United States 

Department of 

Agricu It ure 

Forest Service 

Pacific Northwest 

Forest and Range 

Experiment Station 

Genera I Tech n i ca I 

Report 

PNW-150 

February 1983 

Western Redcedar -- 

A Literature Review 

Don Minore 

. .. . 

s' 

B 

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 EDITOR'S
DON MINORE is plant ecologist, 

Forestry Sciences Laboratory, 

Pacific Northwest Forest and Range 

Experiment Station, Corvallis, 

Oregon. 
Abstract 

Minore, Don. 

1983. Western redcedar: A 

literature review. USDA For. Serv. 

Gen. Tech. Rep. PNW-150, 70 p. 

Pac. Northwest For. and Range 

Exp. Stn., Portland, Oreg. 

This report is a comprehensive compilation of information on western 

redcedar (Thuja plicata Donn) - its 

occurrence and abundance; associated plant species; morphology and 

anatomy; products; medical aspects; 

diseases; insect, bird, and mammal. 

pests; genetics; horticulture; physiology; ecology; mensuration; and 

si lvicu I t ure. Management recommendations and an extensive list of 

references are included. 

Keywords: Western redcedar, Thuja 

plicata, silviculture, ecology, 

physiology, products. 

Contents 

1 Introduction 

1 Occurrence and 

Abundance 

Range 

Volumes 

3 Associated Plant Species 

Trees 

Shrubs 

Herbs 

Major Communities 

12 Morphology, Anatomy, 

and Composition 

Form 

Crown, Branches, and 

Strobili and Seeds 

Roots 

Bark 

Wood 

Foliage 

18 Products 

Uses and Properties 

Prices 

Lumber 

Shakes and Shingles 

Poles and Piling 

Pulp 

Veneer and Plywood 

Waste Utilization 

Extractives 

24 Medical Aspects 

24 Insects 

Bark Beetles 

Wood Borers 

Defoliators 

Seed and Cone Insects 

Miscellaneous Insects 

Extractives and Insects 

27 

30 

30 

30 

31 

41 

45 

48 

48 

49 

50 

51 

Diseases 

Seedling Diseases 

Foliage Fungi 

Root and Butt Rots 

Stem Diseases 

Trunk Rots 

Product Decay 

Extractives and Decay 

Birds and Mammals 

Genetics 

Horticulture 

Physiology and Ecology 

Meteorological 

Influences 

Fire 

Soils 

Nutrients and Nutrition 

Asexual Reproduction 

Sexual Reproduction 

Phenology 

Regenerat ion 

Shade Tolerance 

Succession 

Growth 

Productivity 

Mensuration 

Si lvicu I tu re 

Seeding 

Nursery Practices 

Stand Culture and 

Improvement 

Harvesting 

Discussion 

Recommendations 

for Management 

Acknowledgment 

Common and Scientific 

Names of Trees 

Ll tera t ure CI ted 
lntroduct ion 

The western redcedar is the only 

Thuja species native to western 

North America.J (Northern whitecedar grows in eastern North 

America, and four other Thuja 

species occur in the Orient.) These 

members of the subfamily Thujoideae of the Cupressaceae are 

considered more highly evolved than 

Libocedrus, Cupressus, Chamaecyparis, or Juniperus species (see 

Moseley 1943).3 Large western 

redcedars reach ages of 800 to 1,000 

years, and some individuals in 

eastern Washington may be 2,000 

years old (Sharpe 1974). General attributes of the species include a 

conical form with large and fluted 

base in mature trees, drooping 

branches, thin fibrous bark, and 

small scalelike leaves arranged in 

flat sprays (Sudworth 1908, Sharpe 

1974). 

Redcedar wood is valuable and used 

extensively. Use of redcedar products is far ahead of the management practices for replenishing the 

supply of high-quality timber from 

which most of those products are 

made. More efficient use of western 

redcedar and better management 

are needed; they can best be 

achieved by using available 

knowledge as a base for further advances. Considerable knowledge is 

available, but it is scattered in 

diverse publications under many 

subject headings and titles. This 

report summarizes most of the information in those publications for the 

scientists, administrators, and 

foresters who participate in western 

redcedar research, use, and 

si Iviculture. 

lNomenclature for all northwestern plant 

species is according to Hitchcock and 

Cronquist 1973. Scientific names for 

trees mentioned by common name 

throughout the text are listed on 

page 50. 

?Where information was derived from a 

publication, but not specifically stated 

therein, the author's name is prefaced by 

"see" (e.g., see Little 1971). 

Occurrence and Abundance 

Range 

Western redcedar grows along the 

Pacific coast from northern California to southeastern Alaska (fig. 1). It 

occurs sporadically at its southern 

limit in Humboldt County, California, 

where it is common only in the 

lower Mad River drainage and the 

wet region south of Ferndale (Griffin 

and Critchfield 1972). Elsewhere 

along the northern coast of California, western redcedar occurs only in 

isolated stands on boggy habitats. 

North of the California-Oregon 

border, the natural range of western 

redcedar broadens to include portions of the Cascade Range. On the 

western slopes of the Cascades, 

redcedar grows from Crater Lake 

north (Boyd 1959, Little 1971). On the 

eastern slopes, it occurs north of 

approximately 44'30'N latitude 

(Franklin and Dyrness 1973). The 

redcedar populations of the 

Cascades and the coast meet occasionally in moist portions of the 

Willamette Valley, Oregon. Farther 

north, optimal growth and develop 

ment are achieved near the latitudinal center of western redcedar's 

range - the Olympic Peninsula in 

Wash i ng ton. 

North of Vancouver Island, western 

redcedar is restricted to the Coast 

Ranges and coastal islands. The 

northern limits of its coastal range 

are the northern and western shores 

of Sumner Strait on Kupreanof and 

Kuiu Islands and the Petersburg 

vicinity on Mitkof Island (Harris and 

Farr 1974) at approximately 56'30'N 

latitude (see Andersen 1953). South 

of Petersburg, western redcedar occurs as an overstory dominant on 

former muskeg areas with shallow 

water tables (Stephens et al. 1970). 

It is common and important only farther south, however, near Ketchikan 

and Craig, in the intermediate types 

between bogs and upland forests 

(Neiland 1971). 

Figure 1 .-The natural range of western 

redcedar (from Little 1971, Viereck and 

Little 1975). 

1 
Near the southern border of British 

Columbia, a few scattered populations of western redcedar occur between the Coast Ranges and Selkirk 

Mountains, but the coastal range is 

essentially isolated from the interior 

range of the species. The northern 

limit of the interior range is on the 

western slope of the Continental 

Divide at 54'30'N latitude. The interior range extends south in British 

Columbia through the Selkirk Mountains into western Montana and 

northern Idaho (Boyd 1959). The 

southern limit of the interior range 

is in western Montana's Ravalli 

County at 45'50'N latitude (see Little 

1971). With the possible exception - 

of a few trees east of the Continental Divide near the upper end of St. 

Mary's Lake, the eastern limit is 

near Lake McDonald in Glacier National Park (Aller 1960). 

Western redcedar grows from sea 

level to 915 m (3,000 ft) in southeastern Alaska (Viereck and Little 

1972). In British Columbia, the elevation range is higher - from sea 

level to 1200 m (3,900 ft) (Anderson 

1961). Interior redcedar is found 

from 320 m (1,050 ft) near Orofino, 

Idaho (personal communication, 

Charles A. Wellner, Forestry 

Sciences Laboratory, Moscow, 

Idaho), to 2100 m (7,000 ft) (Boyd 

1959). The greatest range in elevation occurs in Oregon, however, 

where western redcedar occurs from 

sea level to 2300 m (7,500 ft) at the 

rim of Crater Lake (Sudworth 1908, 

Bowers 1956). 

Coastal populations of western 

redcedar receive from less than 89 

to more than 660 cm (less than 35 to 

more than 260 in) of annual rainfall. 

Interior populations receive about 71 

cm (28 in) in the north, 81 to 124 cm 

(32 to 49 in) of annual precipitation 

farther south (Boyd 1959). 

Where sufficient precipitation is 

present, temperature apparently 

limits the range of western redcedar. 

Schmidt (1958) measured an abrupt 

decrease in length of the frost-free 

period just above the upper elevational limits of western redcedar, 

western hemlock, and Douglas-fir on 

Vancouver Island. In southeastern 

Alaska, the northern limits of 

western redcedar are not correlated 

with rainfall or winter temperatures, 

but they are between the 11.1" and 

11.7"C (52" and 53°F) mean summer 

temperature isotherms (Andersen 

1953, 1955a). Average annual temperatures in inland portions of the 

redcedar range are lower than those 

along the coast (see Boyd 1959). 

Western redcedar is often grown 

outside its natural range. In the 

United States, planted trees grow as 

far north as Juneau, Alaska (Harris 

and Farr 1974), and western redcedar is occasionally cultivated as 

an ornamental tree in the Middle 

and North Atlantic States (Sargent 

1933). Redcedars have been 

cultivated as ornamentals in the 

Ukraine since 1870 (Unasylva 1950, 

Perepadya 1971). They are also used 

as ornamentals and hedge trees in 

southern Australia (Streets 1962). 

Western redcedar hedges are widely 

used in Britain (Hubbard 1950) and 

in Switzerland (see Keller 1974). 

For years western redcedar has 

been used in practical forestry in 

England, Ireland, Scotland, and 

Wales (see Keatinge 1947, Zehetmayr 1954, Ovington and Madgwick 

1957, O'Carroll 1967, Aldhous and 

Low 1974, Priest 1974, Carey and 

Barry 1975). It is also well established as a useful forestry species 

in West Germany (see Zimmerle and 

Linck 1951, Borchers 1952, Degen 

1965, Hesmer and Gunther 1968, 

Volk 1968), East Germany (see 

Lembcke 1970), and Austria (see 

Rannert 1976). Indeed, the species is 

almost naturalized in West Germany 

(Volkert 1956). Experimental redcedar stands were established in 

Poland in 1890 (see Gecow 1952), 

and the species was recommended 

for practical Jorestry in Czechoslovakia (Holubcik 1968). It has been 

planted in Denmark and France 

since the 1860's (see Sgegaard 

1956b, Guinier 1951). Western 

redcedar plantations also have been 

established in Italy (Minister0 

dell'Agricoltura e delle Foreste, Collana Verde, Roma 1965). Redcedar 

has been grown in western Norway 

(Smitt 1950), but the northernmost 

stands on record are in Mustila, 

Finland, at 60'41 'N latitude (Artsybashev 1939). 

Western redcedar has been planted 

extensively in New Zealand (see 

Perham 1938, Hocking and Mayfield 

1939, Ranger 1945, Streets 1962, and 

Weston 1971). It has also been successfully grown at higher elevations 

in Tasmania, but it grows relatively 

slowly in Kenya (Streets 1962). The 

species has shown little promise in 

the Union of South Africa (Streets 

1962) or in central Honshu, Japan 

(see Kawada and Yamaji 1949). 

Volumes 

Western redcedar is an important 

commercial species in much of its 

natural range. In North America, an 

estimated volume of 154 billion 

board feet (Scribner rule) exists in 

live western redcedar trees that are 

at least 25 percent sound (Bolsinger 

1979). More than three-fourths of 

this volume (120 billion board feet 

by Bolsinger's estimate) occurs in 

British Columbia. Within British Columbia, 86 percent of the western 

redcedar volume is found in coastal 

areas (British Columbia Forest Service, Inventory Division 1967). The 

rest grows in the interior. When all 

trees larger than 25.4 cm (10 in) in 

diameter are considered, western 

redcedar accounts for about 11 percent of all the sound wood in 

2 
Associated Plant Species 

mature, accessible commercial 

forests in British Columbia. In 

coastal areas, this proportion rises 

to 39 percent (Gardner 1963). When 

only the north coast forests of 

British Columbia are considered, 

western redcedar makes up 52 percent of the merchantable volume 

(McBride 1959). Although much of 

British Columbia’s vast cedar 

resource is sawtimber, an estimated 

121 million western redcedar poles 

also were included in 1961 (Anderson 1961). 

In the United States, most western 

redcedars (13 billion board feet) 

grow in Washington. The greatest 

concentration is on the Olympic 

Peninsula in Clallam, Grays Harbor, 

and Jefferson Counties, where an 

additional 10 percent of the present 

live volume probably exists as dead 

cedars that are at least 25 percent 

sound (Bolsinger 1979). Bolsinger’s 

compilations show that Idaho has 

7.8 billion, Alaska 6.3 billion, Oregon 

5 billion, Montana 1.4 billion, and 

California 76 million board feet of 

cedar volume. Three-fifths of it is in 

the National Forests, where most of 

the redcedar in Idaho, Montana, and 

Alaska occurs. 

Bolsinger found that 66 percent of 

all western redcedar volume in the 

United States is in trees that are 

59cm (21-in) d.b.h. or larger, 44 percent is in trees larger than 74 cm (29 

in). Average size is largest in Washington and smallest in Idaho. Most 

of the redcedar volume in Idaho occurred in 28- to 53-cm (1 1 .O-to 

20.9-in) d.b.h. trees in 1962 (see 

Wilson 1962). 

Trees 

Pure western redcedar stands cover 

some small areas (Eyre 1980), but 

the species usually is associated 

with other tree species. These species are listed by locality in table 1. 

Soil moisture conditions seem to be 

important in determining composition of local stands. Black cottonwood and bigleaf maple often grow 

with western redcedar in swamps 

(Sharpe 1974), as do both Pacific 

silver fir and western white pine in 

coastal swamps of the Olympic 

Peninsula (Franklin and Dyrness 

1973). Dry-site associates include 

grand fir and lodgepole (shore) pine 

along the east coast of Vancouver 

Island (Packee 1976), Pacific 

madrone on the British Columbia 

mainland (see Krajina 1969), and 

western hemlock on the Queen 

Charlotte Islands (Day 1957). 

Western hemlock and black cottonwood are associated with western 

redcedar throughout its natural 

range. Douglas-fir is present in all 

but the Alaska range. Pacific yew 

occurs only in the extreme south 

end of southeastern Alaska (Viereck 

and Little 1972), but it is often found 

as a redcedar associate elsewhere. 

Western redcedar is a major species 

in two forest cover types recognized 

by the Society of American 

Foresters (Eyre 1980) - Western 

Redcedar and Western RedcedarWestern Hemlock. It occurs as a 

minor associated species in 10 

types: Western Hemlock-Sitka 

Spruce, Coastal True Fir-Hemlock, 

Douglas-Fir-Western Hemlock, 

Pacific Douglas-Fir, Port-OrfordCedar, Western Larch, Western 

White Pine, Engelmann SpruceSubalpine Fir, Red Alder, and Redwood. 

Rubus parviflorus Nutt. is associated with western redcedar from 

Alaska to California and from 

coastal Washington and Oregon to 

Montana (table 2). Several other 

shrub associates occur in both interior and coastal environments 

(e.g., Amelanchier alnifolia Nutt., 

Cornus stolonifera Michx., Menziesia ferruginea Smith, Oplopanax 

horridum (Smith) Miq., Pachistima 

myrsinites (Pursh) Raf., Rosa gymnocarpa Nutt., and Symphoricarpos 

albus (L.) Blake), but some associated shrubs are more limited. Sorbus, Lonicera, and Clematis species 

are found with redcedar only in the 

interior; Rubus spectabilis Pursh 

and Vaccinium parvifolium Smith 

are associated only near the coast. 

Shrub associates change less with 

latitude than they do with longitude, 

but two are noteworthy. Rhododendron macrophyllum G. Don is abundant in coastal California, Oregon, 

and Washington; it seems to be 

present in only two stands in 

southern British Columbia, however 

(see Packee 1976). In contrast, the 

northern limits of Gaultheria shallon 

Pursh are nearly the same as the 

northern limits of western redcedar 

in coastal Alaska (see Viereck and 

Little 1972, 1975). 

3 
Table 1 - Tree species associated with western redcedar in 7 portions of its natural range 

Alaska' Coastal British Columbia2 Interior British Columbias Montana4 

Abies amabilis 

Alnus rubra 

Chamaecyparis nootkatensis 

Picea sitchensis 

Pinus contorta 

Populus trichocarpa 

Taxus brevifolia 

Tsuga heteroph ylla 

Abies amabilis 

Abies grandis 

Acer macroph yllum 

Alnus rubra 

Arbutus menziesii 

Betula papyrifera 

Chamaecyparis nootkatensis 

Corn us nut ta llii 

Picea sit c h en s is 

Pinus contorta 

Pinus monticola 

Populus tremuloides 

Populus trichocarpa 

Pseudotsuga menziesii 

Quercus garryana 

Tax us brevi f o lia 

Tsuga heterophylla 

Tsuga mertensiana 

Abies grandis 

Abies la s ioca rpa 

Betula papyrifera 

Larix occiden talis 

Picea engelmannii 

Picea glauca 

Pinus albicaulis 

Pinus contorta 

Pinus monticola 

Populus tremuloides 

Populus trichocarpa 

Pseudotsuga menziesii 

Taxus brevifolia 

Tsuga heterophylla 

Abies grandis 

Abies lasiocarpa 

Betula papyrifera 

Larix occidentalis 

Picea engelmannii 

Picea glauca 

Pinus contorta 

Pinus monticola 

Pinus ponderosa 

Populus trichocarpa 

Pseudotsuga menziesii 

Taxus brevifolia 

Tsuga heteroph ylla 

IFrom Viereck and Little (1972). 

ZFrom Orloci (1961, 1965), Krajina (1969), Packee (1976). 

3From McLean and Holland (1958), Bell (1965), Krajina (1969). 

4From Pfister et al. (1977). 

sFrom Daubenmire (1952), Daubenmire and Daubenmire (1968). 

6From Franklin and Dyrness (1973), Dyrness et al. (1974). 

'From Munz and Keck (1959), Axelrod (1977), Kuchler (1977), Sawyer et al. (1977), Zinke (1977). 

4 
Table 1 - Continued 

Eastern Washington Western Washington 

and northern Idaho6 and Oregone Calif ornla7 

Abies grandis 

Abies lasiocarpa 

Betula papyrifera 

Larix occidentalis 

Picea engelmannii 

Pinus contorta 

Pinus monticola 

Pinus ponderosa 

Populus tremuloides 

Populus trichocarpa 

Pseudotsuga menziesii 

Taxus brevifolia 

Tsuga heterophylla 

Abies amabilis 

Abies grandis 

Abies procera 

Acer macroph yllum 

AInus rubra 

Arbutus menziesii 

Calocedrus decurrens 

Castanopsis chrysoph ylla 

Chamaecyparis la wsoniana 

Chamaecyparis nootkatensis 

Cornus nuttallii 

Lithocarpus densiflorus 

Pinus contorta 

Pinus monticola 

Picea engelmannii 

Picea sitchensis 

Populus tremuloides 

Populus trichocarpa 

Pseudo t s uga m enzies ii 

Taxus brevifolia 

Tsuga heteroph ylla 

Tsuga mertensiana 

Abies grandis 

Acer macroph yllum 

Alnus rubra 

Chamaecyparis la wsoniana 

Corn us nut ta llii 

Lithocarpus densiflorus . 

Picea sit c h en s is 

Populus trichocarpa 

Pseudo tsuga menziesii 

Rhamnus purshiana 

Sequoia sempervirens 

Tsuga heterophylla 

Um bellula ria calif ornica 

5 
Table 2 - Shrub species associated with western redcedar in 7 portions of its natural range 

Alaska' Coastal British Columbia2 interior British Columbiaa Montana4 

Amelanchier alnifolia 

var. semiin tegrif olia 

Alnus sinua ta 

Cla do tha mn us p yroli f lorus 

Cornus s tolonifera 

Gaultheria shallon 

M enziesia f erruginea 

Oplo pa n a x horrid um 

Ribes bracteosum 

Ribes laxiflorum 

Rubus parviflorus 

Rubus spectabilis 

Salix barcla yi 

Salix scouleriana 

Salix sitchensis 

Sambucus racemosa ssp. 

Vaccinium alas kaense 

Vaccinium ovalifolium 

Vaccinium parvifolium 

Va ccin ium uligin os um 

Viburnum edule 

pubens var. arborescens. 

Acer circina tum 

Alnus sinuata 

A m ela nchier a In if olia 

Berberis nervosa 

Cla do tha mn us p yroli f lorus 

Cornus stolonifera 

Gaultheria shallon 

Holodiscus discolor 

Menziesia ferruginea 

Myrica gale 

Oplopanax horridum 

Physocarpus capitatus 

Prunus emarginata 

Ribes bracteosum 

Rosa gymnocarpa 

Rubus parviflorus 

Rubus spectabilis 

Rubus ursinus 

Sa lix s couleria na 

Sambucus ovatum 

Sambucus racemosa 

ssp. pubens 

Spiraea douglasii 

Symphoricarpos albus 

S ymphoricarpos mollis 

Va ccinium a la s ka ense 

Vaccinium m yrtillus 

Va ccinium ova li f olium 

Vaccinium ovatum 

Vaccinium parvifolium 

Vaccinium uliginosum 

Viburnum opulus 

var. america num 

A cer gla brum 

Amelanchier alnifolia 

Arctostaphylos uva-ursi 

Ceanothus sanguineus 

Cladothamnus pyroliflorus 

Cornus stolonifera 

Gaultheria ova ti f olia 

Gaultheria shallon 

Juniperus communis 

Lonicera ciliosa 

Lonicera involucrata 

Lonicera utahensis 

Menziesia ferruginea 

Oplopanax horridum 

Pachystima m yrsinites 

Prunus emarginata 

Rhododendron albiflorum 

Ribes lacustre 

Ribes viscosissimum 

Rosa gymnocarpa 

Rubus nivalis 

Rubus parviflorus 

Sa lix s couleriana 

Sambucus racemosa 

ssp. pubens 

Shepherdia canadensis 

Sorbus sitchensis 

Spiraea be tulif olia 

Spiraea dougla sii 

Vaccinium membrana ceum 

Vaccinium m yrtillus 

Vaccinium ovalifolium 

Viburnum edule 

Viburnum opulus 

var. lucida 

var. americanum 

Acer gla brum 

Alnus incana 

var. occidentalis 

Am ela n ch ier a In if o lia 

Arctostaphylos uva-ursi 

Berberis aqui folium 

Berberis repens 

Ceanothus velutinus 

Clematis columbiana 

Cornus stolonifera 

Holodiscus discolor 

Lonicera utahensis 

Menziesia ferruginea 

Menziesia glabella 

Oplopanax horridum 

Pach ystima m yrsinites 

Ribes lacustre 

Rosa gymnocarpa 

Rubus parviflorus 

Salix sp. 

Shepherdia canadensis 

Sorbus sitchensis 

Sorbus scopulina 

Spiraea betuli f olia 

S ymp horicarpos a lbus 

S ymp horicarpos occiden ta lis 

Vaccinium globulare 

Vaccinium membranaceum 

Vaccinium m yrtillus 

Va ccinium scopa rium 

var. lucida 

'From Viereck and Little (1972); personal communication from Paul Alaback, Department of Forest Science, Oregon 

State University, Corvallis, 1980. 

2From Orloci (1961, 1965), Krajina (1969), Packee (1976). 

3From McLean and Holland (1958), Bell (1965), Krajina (1969). 

4From Aller (1960), Pfister et al. (1977). 

5From Daubenmire (1952), Daubenmire and Daubenmire (1968). 

eFrom Fonda and Bliss (1969), Franklin and Dyrness (1973), Dyrness et al. (1974). 

7Fr~m Munz and Keck (1959), Axelrod (1977), Kuchler (1977), Sawyer et al. (1977), Zinke (1977). 

6 
Table 2 - Continued 

Eastern Washlngton and Western Washlngton 

northern Idaho6 and Oregon6 Calif ornla7 

Acer glabrum 

Ainus sinuata 

Amelanchier alnifolia 

Arctostaphylos uva-ursi 

Clematis columbiana 

Cornus stolonifera 

Corylus cornuta 

Lonicera utahensis 

M enziesia f errugin ea 

Oplopanax horridum 

Pachystima m yrsinites 

Ribes lacustre 

Ribes viscosissimum 

Rosa gymnocarpa 

Rubus idaeus 

Rubus parviflorus 

Sambucus racemosa 

ssp. pubens 

Sorbus scopulina 

Spiraea be tuli f olia 

var. lucida 

S ym p horica rpos a lbus 

Vaccinium membranaceum 

Vaccinium ova lifolium 

Acer circina tum 

A melanchier a In if olia 

Berberis nervosa 

Corylus cornuta 

Gaultheria shallon 

Menziesia ferruginea 

Oplopanax horridum 

Pachystima m yrsinites 

Rhododendron macrophyllum 

Ribes lacustre 

Rosa gymnocarpa 

Rosa nutkana 

Rubus nivalis 

Rubus parviflorus 

Rubus ursinus 

Rubus specta bilis 

Salix hookeriana 

Sorbus sitchensis 

Spiraea douglasii 

Symphoricarpos albus 

S ymphoricarpos mollis 

Vaccinium alaskaense 

Va ccinium membrana ceum 

Va cciniurn ova li f olium 

Vaccinium ovatum 

Vaccinium parvifolium 

Acer circina tum 

Berberis nervosa 

Corylus cornuta 

Gaultheria shallon 

Holodiscus discolor 

M yrica ea li f ornica 

Rhododendron macroph yllum 

Rhododendron occidentale 

Ribes bracteosum 

Rosa gymnocarpa 

Rubus parviflorus 

Rubus spectabilis 

Rubus ursinus 

Vaccinium ovatum 

Va ccin ium pa rvi f olium 

7 
Herbs 

Some of the herbs associated with 

western redcedar are listed in table 

3. Fourteen associates are common 

in both coastal and interior environments: Athyrium filix-femina (L.) 

Roth., Chimaphila umbellata (L.) 

Bart., Clintonia uniflora (Schult.) 

Kunth., Cornus canadensis L., 

Dryopteris austriaca (Jacq.) Woynar, 

Galium trifidum L., Gymnocarpium 

dryopteris (L.) Newm., Linnaea 

borealis L., Polystichum munitum 

(Kaulf.) Presl, Pteridium aquilinum 

(L.) Kuhn., Rubus pedatus J. E. 

Smith, Streptopus amplexifolius (L.) 

DC., Tiarella trifoliata L., and Viola 

glabella Nutt. Two other common 

associates (Carex obnupta Bailey 

and Oenanthe sarmentosa Presl) are 

limited to moist habitats west of the 

Cascades. Aralia nudicaulis L. and 

Coptis occidentalis (Nutt.) T. & G. 

occur with redcedar only in the 

interior. 

Major Communities 

Krajina (1969) described 23 British 

Columbia “Biogeocoenoses” that 

contain western redcedar as a component. The communities represented are listed in table 4. The 

communities of Orloci (1961, 1965) 

and Brooke (1965) on the southwestern British Columbia mainland also 

are listed in table 4. ThujalPolystichum occurs on moist, concave 

lower slopes. ThujalLysichitum also 

occurs on lower slopes, but only in 

swampy situations and on wet outwash terraces where the ground 

water table is near the surface and 

flowing. ThujalCoptis is found in 

swampy depressions where the 

ground water is stagnant, and Thuja/ 

Oplopanax occurs in swampy 

ravines where the ground water 

overf I ows i n t erm it t en t l y. Thuja-A bies 

a ma bilislOplopa nax occ u rs a I on g 

stream margins at 1067- to 1219-m 

(3,500- to 4,000-ft) elevations where 

nonstagnant ground water is near 

the surface. It is of limited occurrence. 

Three of Bell’s (1965) major plant 

communities for the Selkirk and 

Monashee Mountains of southeastern British Columbia include 

western redcedar. The Aralia/ 

Gym n oca rpium co m m u n it y occ u rs 

on slopes and alluvial flats where 

subsurface water is available. 

Oplopanax communities are found 

on steep lower slopes with permanent seepage at or near the surface 

and on alluvial flats with high water 

tables. The Lysichitum community is 

present where soil is saturated by 

slowly moving ground water for 

much of the growing season. A 

si m i I a r ThujalL ysic hitum com m u n it y 

occurs in the coastal environment of 

Vancouver Island’s Nanaimo River 

Valley (see McMinn 1960). 

Daubenmire and Daubenmire (1968) 

recognized three western redcedar 

communities in northern Idaho. 

Thuja plica talPachis tima myrsinites 

is an upland community where 

Athyrium is absent or short and 

Tsuga is absent. Hanley’s (1976) 

biomass estimates indicate that this 

community is very productive. Thuja 

plica talOplopa nax h orridum and 

Thuja plicatalA thyrium filix-femina 

occur on bottomlands where 

Athyrium is usually abundant and 

tall. Oplopanax is present in the 

former, absent in the latter. 

Three additional Idaho redcedar 

communities occur on the North 

Fork of the Clearwater River: Thuja 

plicatalAdiantum pedatum is common, Thuja plicatalDryopteris spp. is 

uncommon, and Thuja plicatal 

Lysichitum americanum is rare 

(Steele 1971). A fourth (Thuja 

plicatalAsarum caudatum) is common in Nezperce County, Idaho 

(Steele et al. 1976). 

Pfister et al. (1977) described two 

western redcedar communities in 

Montana that are essentially similar 

to the Daubenmires’ communities in 

Idaho - Thuja plicatalOplopanax 

horridum and Thuja plicatalClintonia 

uniflora. The latter corresponds to 

the Daubenmires’ Thuja plicatal 

Pachistima myrsinites community, 

but it includes a Menziesia ferruginea phase not present in Idaho. 

Two unnamed communities described by McLean and Holland 

(1958) in the upper Columbia River 

Valley also correspond to the 

Dau benmires’ ThujalOplopanax and 

Th ujalPa c h is t im a co m m u n it i es. 

Bailey (1966) described a Thuja 

plica talAdiantum peda tum-A thyrium 

filix-femina community in the 

southern Oregon Coast Ranges of 

eastern Coos and western Douglas 

Counties. Polystichum munitum and 

Oxalis oregana dominated the herb 

layer, but Bailey used the high constancy, low cover Adiantum and 

Athyrium as indicator species for 

this community. It occurred at low 

elevations on steep lower and middle slopes. 

Franklin and Dyrness (1973) summarized the community information 

available from Oregon and Washington in 1973. They included two San 

Juan Island communities described 

in a 1973 rep0rt.Y Thuja plicataAbies grandislPachistima myrsinites 

occurs on moderately moist, northfacing slopes and level areas in the 

interior of Sucia Island. The 

moistest sites in the interior valley 

of Sucia Island support Thuja 

plicata-A bies grandislPolystichum 

munitum. A report9 is cited by 

Franklin and Dyrness (1973) in referring to a Thuja plicata-Acer circinatumlherb community found in 

moderately moist valleys of Washington’s North Cascades National 

Park. Finally, Franklin and Dyrness 

(1973) described and photographed 

the Thuja plicata- Tsuga heterophyllalOplopanax horridumlA thyrium 

filix-femina community. It occurs on 

very wet slopes and stream terraces 

in western Washington and is characterized by an extremely lush 

understory. 

3Unpublished report, “Preliminary report 

on the vegetation of the San Juan 

Islands, Washington,” by R.W. Fonda 

and J.A. Bernardi. 1973. On file, Forestry 

Sciences Laboratory, Corvallis, Oregon. 

4Unpublished report, “Phytosociological 

reconnaissance of western redcedar 

stands in four valleys of the North 

Cascades Park complex,” by Joseph W. 

Miller and Margaret M. Miller. 1970. On 

file, Forestry Sciences Laboratory, Corvallis, Oregon. 

8 
Table 3 - Herb species associated with western redcedar in 7 portions of its natural range 

Alaska' Coastal British Coiumbla* interior British Columbia' Montana' 

Athyrium filix-femina 

Blechnum spicant 

Clintonia uniflora 

Copt is a s p len if o lia 

Cornus canadensis 

Dryopteris austriaca 

Epilobium a lpinum 

var. nutans 

G ymnocarpium dryopteris 

Hypopitys monotropa 

Listera cordata 

L ysichitum americanum 

Maianthemum dila tatum 

Polypodium glycyrrhiza 

Pteridium aquilinum 

Pyrola uniflora 

Rubus pedatus 

S trep top us am plex if olius 

S trep top us rose us 

var. curvipes 

Streptopus streptopoides 

Thelyp teris p hegop teris 

Tiarella trifoliata 

Achlys triph ylla 

Adiantum pedatum 

Anemone occidentalis 

A th yrium f ilix- f em ina 

Blechnum spicant 

Cardamine breweri 

Carex deweyana 

Carex hendersonii 

Carex obnupta 

Carex pauciflora 

Chimaphila menziesii 

Chimaphila umbellata 

Circaea alpina 

Clintonia uniflora 

Cop tis a spleni f olia 

Coptis trifolia 

Corallorhiza maculata 

Cornus canadensis 

Disporum hookeri 

Drosera rotundifolia 

Dryopteris austriaca 

Epilo bium angus ti f olium 

Equisetum telma teia 

Eriop h orum cham is s o n is 

Galium trifidum 

Glycera elata 

Glycera striata 

Goodyera oblongifolia 

G ymnocarpium dryopteris 

Linnaea borealis 

Listera caurina 

Listera cordata 

Lycopodium clava tum 

Lycopodium complanatum 

Lycopodium selago 

L ysichitum americanum 

Maianthemum dilatatum 

Mimulus moschatus 

Mitella ovalis 

Monotropa uniflora 

Montia sibirica 

Oenanthe sarmentosa 

Polysticum munitum 

Pteridium aquilinum 

Rubus pedatus 

Scirpus m icroca rpus 

Smilacina stellata 

Stachys mexicana 

Stellaria crispa 

Strep top us am plexi f olius 

Streptopus roseus 

var. curvipes 

Streptopus streptopoides 

Tia re Ila tri f o lia t a 

var. laciniata 

Tiarella trifoliata 

var. trifolia ta 

Tiarella trifoliata 

var. unifoliata 

Tofieldia glutinosa 

Trillium ova tum 

Trise t um cern uum 

Veratrum viride 

Viola glabella 

Viola orbicula ta 

Adenocaulon bicolor 

Adiantum pedatum 

Angelica arguta 

Aralia nudicaulis 

A th yrium f ilix- f em ina 

Campanula rotundif olia 

Carex disperma 

Carex laeviculmis 

Carex stipata 

Chimaphila um bella ta 

Circaea alpina 

Clintonia uniflora 

Corallorhiza maculata 

Corallorhiza mertensiana 

Cornus canadensis 

Corydalis sempervirens 

Dryopteris a ustria ea 

Equisetum palustre 

Equisetum scirpoides 

Equisetum sylvaticum 

Fragaria virginiana 

var. glauca 

Galium boreale 

Galium trifidum 

Geum macrophyllum 

Glycera elata 

Good yera o blongif olia 

G ymnocarpium dryopteris 

Heuchera c ylindrica 

Linnaea borealis 

Listera caurina 

Lis tera con va llarioides 

Actaea rubra 

Adenocaulon bicolor 

Aralia nudicaulis 

Athyrium filix-femina 

Carex disperma 

Chimaphila umbellata 

Circa ea a lpina 

Clintonia uniflora 

Cop tis occiden talis 

Cornus canadensis 

Disporum hookeri 

Disporum trach ycarpum 

Galium boreale 

Galium trifidum 

Goodyera oblongifolia 

G ymnocarpium dryopteris 

Linnaea borealis 

Listera borealis 

Lis tera con valla rioides 

Lycopodium annotinum 

Lycopodium complana tum 

Polystichum munitum 

Pteridium aquilinum 

Pyrola a sari f olia 

Pyrola chloran t ha 

Pyrola secunda 

Smilacina stellata , 

Smila cina racemosa 

Strep topus a mplexi f olius 

Tiarella trifoliata 

var. trifoliata 

Tiarella trifoliata 

Lycopodium complanatum var. unifoliata 

Lysichitum americanum Trillium ovatum 

Melamp yrum lineare 

Mitella breweri Veratrum viride 

Mitella pen tandra 

Polypodium glycyrrhiza Viola glabella 

Polystichum andersonii Viola orbiculata 

Polystichum lonchitis Xeroph yllum tenax 

Pteridium a quilin um 

Pyrola asari f olia 

Pyrola chlorantha 

Pyrola picta 

Pyrola secunda 

Rubus pedatus 

Scirpus microcarpus 

Smilacina stellata 

Smilacina racemosa 

S trep top us a mplexi f olius 

Streptopus roseus 

var. curvipes 

Streptopus streptopoides 

Thalictrum occiden tale 

Tiarella trifoliata 

var. laciniata 

Tiarella trifoliata 

var. trifoliata 

Tiarella trifolia ta 

var. unifoliata 

Trisetum cernuum 

Veratrum viride 

Viola adunca 

Viola glabella 

Viola palustris 

Woodsia scopulina 

Va leriana sitch en sis 

Viola ea na dens is 
Table 3 - Continued 

Eastern Washlngton and Western Washington 

northern Idaho6 and Oregone Callfornia7 

Actaea rubra 

Adenocaulon bicolor 

Adiantum pedatum 

Anemone piperi 

Aralia nudicaulis 

Asarum caudatum 

Athyrium filix-femina 

Carex la eviculm is 

Chimaphila menziesii 

Chimaphila umbellata 

Circaea alpina 

Clin tonia uni f lora 

Coptis occidentalis 

Corallorhiza maculata 

Corallorhiza mertensiana 

Corallorhiza trifida 

Cornus canadensis 

Disporum hookeri 

Dryopteris a us tria ca 

Dryopteris f ilix-mas 

Epilobium a ngus ti f olium 

Fragaria vesca 

var. bracteata 

Galium trifidum 

Goodyera oblongifolia 

G ymnocarpium dryopteris 

Hypopitys monotropa 

Linnaea borealis 

Listera caurina 

Lis tera con va llarioides 

L ysichitum americanum 

Mertensia paniculata 

Mitella pentandra 

M it ella s ta uro pe ta la 

Montia sibirica 

Polys tich um m unit um 

Pteridium a quilinum 

Pterospora andromedea 

Pyrola asa ri f olia 

Pyrola chlorantha 

Pyrola picta 

Pyrola secunda 

Pyrola uniflora 

Rubus pedatus 

Smilacina racemosa 

Smilacina stellata 

Stellaria crispa 

Streptopus amplexifolius 

Tiarella trifolia ta 

var. trifoliata 

Tiarella trifolia ta 

var. unifoliata 

Trillium ova tum 

Trisetum cernuum 

Veratrum viride 

Viola glabella 

Viola orbiculata 

Xeroph yllum tenax 

Achlys triphylla 

Adenocaulon bicolor 

Adiantum pedatum 

Anemone deltoidea 

Asarum caudatum 

A th yrium filix- f em ina 

Blechnum spicant 

Campanula scouleri 

Carex obnupta 

C h im a p h ila m enzies ii 

Chimaphila umbellata 

Circaea alpina 

Clin ton ia un if lora 

Coptis laciniata 

Corallorhiza mertensiana 

Cornus canadensis 

Disporum hookeri 

Disporum smithii 

Dryopteris aus triaca 

Galium oreganum 

Galium trifidum 

Goodyera oblongifolia 

G ymnocarpium dryopteris 

Linnaea borealis 

Listera caurina 

Lycopodium clava tum 

Lysichitum americanum 

Maianthemum dilatatum 

Mitella sp. 

Montia sibirica 

Oenanthe sarmentosa 

Osmorhiza purpurea 

Oxalis oregana 

Polystichum munitum 

Pteridium aquilinum 

Pyrola a sari f olia 

Pyrola picta 

Pyrola secunda 

Rubus lasiococcus 

Rubus pedatus 

Smilacina stellata 

Stach ys mexicana 

Streptopus amplexifolius 

Streptopus roseus 

var. curvipes 

Synthyris reniformis 

Tiarella trifoliata 

var. trifoliata 

Tiarella trifoliata 

var. unifoliata 

Tolmiea menzies ii 

Trientalis latifolia 

Trillium ova tum 

Van co uveria hexa n dra 

Viola glabella 

Viola s em pe rviren s 

Whipplea modesta 

Xeroph yllum tenax 

Carex obnupta 

Epilobium angustifolium 

Erechtites arguta 

Erechtites minima 

Oxalis oregana 

Polys tichum m unitum 

Pteridium aquilinum 

Viola sempervirens 

'Personal communication, Paul Alaback, Department of Forest Science, Oregon State University, Corvallis, 1980. 

'From Orloci (1961, 1965), Krajina (1969), Packee (1976). 

3From McLean and Holland (1958), Bell (1965), Krajina (1969). 

'From Aller (1960), Pfister et al. (1977). 

5From Daubenmire (1952), Daubenmire and Daubenmire (1968), Steele (1971). 

6From Fonda and Bliss (1969), Franklin and Dyrness (1973), Dyrness et al. (1974). 

'From Munz and Keck (1959), Axelrod (1977), Kuchler (1977), Sawyer et al. (1977), Zinke (1977). 

10 
Table 4 - Major western redcedar communltles in 5 portions of its native range' 

Eastern Washington Western Washington 

Coastal British Columbiaz interior British Columbiaa Montana4 and northern Idaho' and Oregon' 

Thpl-AbamlOpholGydr-Atfi 

Thpl-Abam-PsmelVaov 

Thpl-Abam-PsmelVaovVaallS t ro- Pom u-B I sp 

T h pl-A bg r- PsmelS yallTi t rPomu 

Thpl-Abgr-Psme/Tit r-Pomu 

Thpl-AbgrlSyallAdpe 

Thpl-Chno-Abam-Psmel 

Vaov-Bene 

Thpl-Pisi-AbamlOphoR i br- R u s pl Pom u 

Thpl-Pisi-Abam-Psmel 

Pomu 

Thpl-Pisi-AlrulLyam/Caob 

T h p I- Pi s i- P i colS pd o 

Thpl-PsmelBene 

Thpl-PsmelPomu-Act r 

Thpl-Psme-Quga/Syal/ 

Pomu 

Psme-Th p IIG ash-Sy moBene 

Tshe-Thpl-Abam-Psmel 

VaallBlsp 

ThpllPomu 

Th p IlVaa IlLyam 

Th p IlCoas-Cot r- Ly am 

Th p I/O p holAd pe 

Th p I- AbamlO p ho 

ThpllLyam 

(1) ThpllLyam (1) ThpllClun (1) ThpllAtfi (1) Th pllAd pe-At f I 

(2) Th p llOp ho/Ti u n (2) ThpllOpho (2) ThpllOpho (2) Th p I-A bg rlPamy 

(3) Thpl-Potr-PienlCostlPyas- (3) ThpllPamy (3) Thpl-AbgrlPomu 

Smst (4) ThpllAdpe (4) Thpl-Accilherbs 

(4) Thpl-PsmelLoinlArnu-GydrCI un-Ti un (6) ThpllLyam 

(5) Thpl-Tshe-Psme-Pimol (7) ThpllAsca 

Pam ylqoca 

(6) Psme-Thpl-PimolVaovPam ylCoca-Ti u n 

(7) Tshe-Thpl-PsmelLoutlArnuGydr-CocaClu n-Tiu n 

(8) Arnu-Gydr 

(5) ThpllDr (5) Th pl-Ts helO p holAt f i 

(9) OPhO 

(10) Lyam 

'Only the first two letters of each genus and species are listed (e.g. Thuja plicata = Thpl). 

2Numbers 1-16 are from Krajina (1969); 17-20 are from Orloci (1965); 21 is from Brooke (1965); 22 is from McMinn (1960). 

SNumbers 1-7 are from Krajlna (1969); 8-10 are from Bell (1965). 

'From Pfister (1977). 

ONumbers 1-3 are from Daubenmire and Daubenmire (1968); 4-6 are from Steele (1971); 7 is from Steele et al. (1976). 

ONumber 1 is from Bailey (1966); 2-5 are from Franklin and Dyrness (1973). 

11 
Morphology, Anatomy, and Composition 

Form 

Western redcedar trees typically attain heights of 60+ m (1979 ft) and 

diameters of 150-300 cm (59-118 in) 

(Franklin and Dyrness 1973), but 

more massive individuals are not uncommon. Trees measuring 4.9 to 

6.1 m (16 to 20 ft) in diameter and up 

to 76 m (250 ft) tall have been found 

(West Coast Lumber Trade Extension Bureau 1927). The largest 

western redcedar known to be alive 

in 1977 grew on the Olympic Peninsula. It was 592 cm (233 in) in 

diameter at breast height and 54 m. 

(178 ft) tall (Pardo 1978). The largest 

redcedar east of the Cascades may 

be a tree 550 cm (216 in) in diameter 

and 54 m (177 ft) high, measured 

recently near Elk River, Idaho (personal communication, Charles A. 

Wellner, Forestry Sciences Laboratory, Moscow, Idaho). 

Large western redcedar trees are 

not uncommon east of the Cascades. A preliminary survey of 

western redcedar in the northern 

Rocky Mountainsy showed 33 

groves containing redcedars larger 

than 152 cm (5 ft) d.b.h. Six contained trees larger than 335 cm (11 

ft) d.b.h. The groves are quite evenly 

distributed among habitat types, but 

the Thuja plicatalA thyrium filixfernina type seems to be most 

typical. Although many groves occur 

on sideslopes, most of the very 

large western redcedars were found 

in stream bottoms or upper basins. 

spaper, “Western redcedar groves in the 

northern Rocky Mountains,” by Frederic 

D. Johnson. 1980. Presented at the 53d 

annual meeting, Northwest Scientific 

Association, in Moscow, Idaho. Abstract 

on file, Forestry Sciences Laboratory, 

Corvallis, Oregon. 

Wherever redcedars grow, the boles 

of old trees tend to be swollen or 

flared at the base (fig. 2). They are 

often conspicuously fluted, with frequent bark seams (Sudworth 1908, 

McBride 1959), but the fluting seems 

to be more common in open-grown 

trees than in dense stands (Nystrom 

1980). Two or more leaders are frequent (Bowers 1956, Day 1957), and 

many old trees have hollow bases 

(McBride 1959, Daubenmire and 

Daubenmire 1968). Mature westerr, 

redcedar trees tend to be larger in 

diameter but shorter than mature 

western hemlock, Sitka spruce, or 

Douglas-fir (Day 1957, Smith et at. 

1961 a). 

Mature western redcedars taper 

more than Douglas-firs and western 

hemlocks. The majority of this taper 

is in the first 16 feet, and most occurs in the first 4 feet above ground 

(Nystrom 1980). Small western redcedar trees seem to taper less than 

large trees, which become nearly 

conical in southeastern Alaska 

(Andersen 1955a). Alaska redcedars 

growing in association with western 

hemlocks have much better form 

than those growing in pure stands 

(Andersen 1955b); this may be 

caused by the greater stand densities associated with hemlockredcedar mixtures. Or it may be the 

result of mixed stands occurring on 

better sites than pure stands (see 

Gregory 1957). 

Most western redcedar trees growing on moderately dry sites in 

western Oregon have rather open 

crowns (see Gratkowski 1956). 

Crown density seems to vary with 

age, however. Young redcedars on 

the Queen Charlotte Islands have 

dense crowns that become thinner 

with age until the upper portions 

die, leaving numerous spike tops 

(Day 1957). This thinning with age 

accompanied by changes in the 

percentages of stem wood, stem 

bark, branches, and foliage in 

western redcedar trees. Branches 

is 

accounted for about 14 percent of 

the aboveground weight of the 5- to 

15-cm (2- to 6-in) d.b.h. redcedars 

measured by Smith and DeBell 

(1973), but only 11 percent of the 

weight of those that were 30 to 41 

cm (12 to 16 in) d.b.h. Individual 

trees vary greatly, however; the two 

redcedars measured by Grier and 

Logan (1977) were 23 and 41 cm (9 

and 16 in) d.b.h. and had about 18 

percent of their weight in living 

branches. 

The branches of young western 

redcedars curve upward. On older 

trees they swing downward near the 

bole, then sweep up again at the 

ends (Bowers 1956). Except where 

densely crowded, most of these 

branches are retained until the trees 

are 46- to 51-cm (18- to 20-in) d.b.h. 

and 15 to 24 m (50 to 80 ft) tall (Sudworth 1908). Tiny branchlets are 

formed when the terminal shoot on 

each branch produces a lateral apex 

at every eighth leaf pair (see 

Malcolm and Caldwell 1971). These 

branchlets (really frondlike aggregations of leaves) die and fall off every 

2 to 5 years (see Sudworth 1908, 

Bowers 1956). 

The leaves of a mature western 

redcedar are small and scalelike - much smaller than the two cotyledons of a germinating seedling or 

the juvenile leaves produced in 

whorls of four soon thereafter (see 

Franklin 1961). They are darker 

green on top and lighter underneath 

than other cedarlike trees of the 

Pacific Northwest (Bowers 1956), 

with white markings on the lower 

surfaces (Dallimore and Jackson 

1967). 

12 
Western redcedar leaves are 

numerous, and foliage comprises a 

higher fraction of the live-crown 

weight in redcedar than it does in 

Douglas

-fir (Brown 1978). Foliage accounts for 10 percent of the aboveground weight of 5- to 15-cm (2- to 6-in) d.b.h. redcedars and 6 percent 

of the weight of 30- to 41 cm (12- to 

16

-in) d.b.h. western redcedars 

(Smith and DeBell 1973). A 0.6- to 

0.9

-m (2- to 3-ft) diameter redcedar 

may have 227 to 1361 kg (500 to 

3,000 Ib) of green foliage (Cochrane 

1951), but Grier and Logan (1977) 

measured an average of only 15.4 kg 

(33.9 Ib) of ovendry foliage on 0.2- 

and 0.4-m (0.8- and 1.3-ft) diameter 

trees. 

Redcedar foliage seems well suited 

to the support of epiphytes. Four 

species of mosses, 1 hepatic, and 

16 lichen species occur on western 

redcedar leaves in western British 

Columbia (Vitt et al. 1973). Daubenmire (1943) also found lichens on the 

leaves of western redcedar in northern Idaho. He described three 

unique attributes that may be 

responsible for the superiority of 

redcedar foliage as an epiphyte habitat: overlapping of the scalelike 

leaves, the surface roughness created by peglike papillae projecting 

from epidermal cells, and a superficial film of scurfy material. Vitt et 

al. (1973) proposed a fourth attribute 

- lack of certain inhibitory volatile 

compounds that are found in the 

foliage of other western conifers. 

E p i p h yt e- i n hi bit i ng com pou nd s may 

not be present, but western redcedar 

foliage contains several other 

substances. The volatile foliage oil 

is chiefly L

-thujone and d-isothujone 

(Von Rudloff 1962), but pinene, d-sabinene, and fenchone are also 

present (Cochrane 1951, Von Rudloff 

1962, Banthorpe et al. 1973). Oil 

from young branchlets contains 

larger amounts of pinene and . 

sabinene than that from older ones 

(Von Rudloff 1962). In addition to the 

above monoterpenes, diterpene 

hydrocarbons (Aplin and Cambie 

1964), biflavonyl pigments (Rahman 

et al. 1972), and dilignol rhamnosides (Manners and Swan 1971, 

1977) have also been found in 

Figure 2.-Old-growth western redcedars. 

Note the fluted, flared lower boles. The 

striped stick is 1 m long. 

western redcedar leaves. Some of 

these compounds inhibit bacterial 

growth (Michel 1976). Those present 

in the steam volatiles obtained from 

redcedar foliage are highly toxic to 

coho salmon fry (Peters 1974, Peters 

et al. 1976). 

13 
The dry, powdered western redcedar 

foliage analyzed by Chow (1977a) 

had a pH of 5.3 - equal to the pH 

of red alder foliage, but much higher 

than the pH values measured for 

Douglas-fir (3.8), western hemlock 

(4.0), lodgepole pine (4.3), or white 

spruce (4.3) foliage. This high pH 

value was accompanied by a high 

calcium content. Ovington (1953) 

analyzed fresh leaves and also 

found higher pH values in redcedar 

than in Douglas-fir or western 

hemlock when all three species 

were measured on the same British 

site. He recorded great variation 

among sites, however, and concluded that leaf pH was related to 

acidity of the underlying soil. 

When litter fall was analyzed near 

the Pacific coast, the calcium concentration in western redcedar 

foliage was over 2 percent - twice 

that of bigleaf maple foliage and 30 

times that of lodgepole pine foliage 

(Tarrant et al. 1951). Calcium content 

was also high in freshly fallen 

western redcedar foliage in the 

northern Rocky Mountains (Daubenmire 1953). Nitrogen and phosphorus 

concentrations were relatively low 

for western redcedar foliage in both 

regions. Potassium concentrations 

were moderately high along the 

coast, moderately low in the northern Rocky Mountains. Packee’s 

(1975) literature review showed that 

crude protein content of western 

redcedar foliage on Vancouver 

Island varies seasonally but is lower 

than that of Douglas-fir foliage. 

Western redcedar foliage apparently 

contains more fat than Douglas-fir 

foliage in July and December, less 

in March. 

Redcedar does not form buds containing preformed shoots (Owens 

and Pharis 1971), and no clearly visible buds or rapidly elongating succulent shoots are present (Aldhous 

and Low 1974). Instead, the shoot 

apex is covered by numerous leaf 

primordia at various stages of 

development. Owens and Pharis 

found that branches are two ranked, 

occurring every two to four nodes. 

Only one branch occurs at a node, 

and secondary branches are more 

abundant on the side closest to the 

apex of the main branch. 

Strobili and Seeds 

Male and female strobili are borne 

on different branches of the same 

tree (Schopmeyer 1974). Both occur 

at the tips of small lateral branches, 

and both are formed as a result of 

the transformation of previously 

vegetative apices (Owens and Pharis 

1971). Male and female strobili occur. 

at different heights, however, and 

they differ in color. The reddish 

male strobili are borne on lower 

branches; the green female strobili 

occur near the treetops (Hedlin 1964, 

SQegaard 1969). The male strobili 

fall off after shedding the pink 

pollen. Pollen grains are single and 

spheroidal, without bladders, apertures, ridges, or folds. They are 20 to 

45 pm in diameter and have scattered, isodiametric radial projections 

(see McAndrews et al. 1973). Western redcedar pollen does not 

preserve well, and it decays rapidly 

in peat bogs (Hansen 1941). 

As the female strobili ripen, they 

change from green to yellow and 

finally to a pale cinnamon-brown 

(Schopmeyer 1974). Erect when 

young, they become reflexed when 

they reach their mature length of 13 

mm (112 in) (Dallimore and Jackson 

1967). Although immature female 

strobili may consist of up to 10 pairs 

of cone scales, only 5 or 6 develop 

to form the mature strobilus and, of 

these, only pairs 3 and 4 are fertile 

(Hedlin 1964). Two or three seeds 

are borne under each fertile scale 

(Bowers 1956). 

Western redcedar seeds are chestnut brown and about 6 mm (114 in) 

long, with lateral wings about as 

wide as the body (Schopmeyer 1974). 

Approximately 9.65 g of cleaned 

seed are obtained per liter of cones 

(0.75 Ib of seed per bushel). Schopmeyer’s 1974 data summary shows 

448,000 to 1,305,000 cleaned seeds 

per kilogram (203,000 to 592,000 

seeds per pound). 

Roots 

The roots of western redcedar may 

be recognized by their extremely 

thin brown outer bark, which is 

underlain by a thin pink to purplered zone above the white inner bark. 

Young roots may have a thick, 

white, pulpy outer layer outside the 

pink zone (Gilbertson et al. 1961). 

The tap roots are poorly defined or 

nonexistent, but a profuse fine root 

system is developed (Leaphart and 

Wicker 1966). These small roots 

decay rapidly and lose most of their 

tensile strength within 3 to 5 years 

after the parent tree is felled. Larger 

redcedar roots may remain 

reasonably sound and intact for 

many years (O’Loughlin 1974). 

Depth of root penetration was 

similar for western redcedar, 

Douglas-fir, and western hemlock 

where Eis (1974) excavated trees on 

Vancouver Island, but Smith (1964b) 

found redcedar roots to be shallower than those of Douglas-fir and 

deeper than western hemlock roots. 

Boyce (1929) mentioned the deep 

root system of western redcedar in 

explaining its windfirmness on the 

Olympic Peninsula. Jackson and 

Knapp (1914), Flint (1925), Hepting 

(1971), and Shinn (1971) refer to 

western redcedar as a shallowrooted species, however, and Haig 

(1936) and Haig et al. (1941) found 

the root penetration poor. Where a 

thick duff layer is present, most 

redcedar roots occur in the duff 

rather than underlying soil (Ross 

1932). Ross found no root hairs on 

these duff-inhabiting roots. Differences in local soil conditions 

probably are responsible for these 

various conclusions. Redcedar may 

form deep root systems on deep, 

moderately dry soils. Its root development is limited and shallow on 

wet sites (see Day 1957, McMinn 

1960). 

All authorities seem to agree that 

western redcedar has an extensive 

root system. Jackson and Knapp 

(1914) believed that bole buttresses 

indicated the number of principal 

roots, with masses of slender 

fibrous roots extending 3 m (10 ft) or 

14 
more in all directions from the buttresses. The ratio of rootlet length 

to the length of the parent lateral 

root was 0.960 for the redcedars examined by Leaphart (1958) in northern Idaho. It was 0.260 for grand fir 

and only 0.005 for lodgepole pine. 

Leaphart and Grismer (1974) measured the extent of roots in a mixedspecies stand in northern Idaho and 

found that western redcedar made 

up only 17 percent of the basal area 

but accounted for 82 percent of the 

root length. 

Root grafting is more frequent in 

western redcedar than in Douglas-fir 

or western hemlock (Eis 1972). In addition to numerous small grafts, Eis 

found 27 grafts greater than 1 cm 

(0.4 in) in diameter between two 

redcedar trees growing on shallow 

soil over bedrock. 

Western redcedar mycorrhizae are of 

the vesicular-arbuscular type (personal communication, James M. 

Trappe, Forestry Sciences Laboratory, Corvallis, Oregon). 

Western redcedar bark is light 

cinnamon-red or brown on young 

trunks, gray on old trees (Isenberg 

1951). It is divided into wide ridges 

by irregular fissures that break up 

the surface into small plates 

(Dallimore and Jackson 1967). 

Redcedar bark is stringy (Wethern 

1959) and, even on old trees, thin. It 

varies from 1.3 to 2.5 cm (1/2 to 1 in) 

thick (Sudworth 1908, lsenberg 1951, 

Bowers 1956, Dallimore and Jackson 

1967). It is slightly heavier than the 

wood, weighing 0.37 to 0.39 g per 

cm3 (23.1 to 24.3 Ibs per ft3) (see 

Smith and DeBell 1973, Brown et al. 

1977). 

Stem bark accounted for about 19 

percent of the aboveground weight 

of 5- to 15-cm (2- to 6-in) d.b.h. trees 

measured by Smith and DeBell, 10 

percent of the weight of 30- to 41-cm 

(12- to 16-in) d.b.h. trees. About 6 

percent of the aboveground weight 

of 23- and 41-cm (9- and 16-in) d.b.h. 

redcedars measured by Grier and 

Logan (1977) consisted of stem bark. 

Smith et at. (1961a) found redcedar 

bark percentages to be slightly 

lower than those of western 

hemlock, much lower than the bark 

percentages of Douglas-fir. When 

Brown et al. (1977) compared bark 

and stem volumes in Montana and 

Idaho, they found the bark volume/ 

stem volume ratio lower in western 

redcedar (0.15) than in ponderosa 

pine (0.24), white pine (0.21), 

Douglas-fir (0.19), western larch 

(0.24), or western hemlock (0.18). 

When they compared bark weight to 

stem weight, the redcedar bark proportion (0.173) was smaller than that 

for all other conifers except 

lodgepole pine (0.1 14). 

For similar tree sizes, redcedar bark 

is slightly thinner than western 

hemlock bark at the top of the first 

4.9-m (16-ft) log in southeastern 

Alaska. It is slightly thicker than 

Sitka spruce or Alaskacedar bark 

measured at that point (see Bones 

1962). Bark thickness varies among 

trees, but the inner bark of western 

redcedar tends to be thinner than 

that of Sitka spruce and its outer 

bark tends to be thicker. Redcedar 

bark has less airspace, lower 

moisture content, and a higher 

specific gravity than Sitka spruce 

bark (see Smith and Kozak 1971). 

Western redcedar has a brown first 

periderm and a reddish purple 

secondary periderm (Mullick 1971). 

The purple color is a property of the 

nonanthocyanic phlobaphene 

pigments found there (Mullick 

1969a). One of these phlobaphenes 

was analyzed and described by 

Swan (1963a). Anthocyanidins are 

also present in the secondary 

periderm (Mullick 1969b). The inner 

and outer bark are similar, but outer 

bark has a higher lignin content 

(Cram et al. 1947). The lignin from 

the outer bark differs from that of 

the inner bark and from most other 

softwoods in that it contains fewer 

methoxyl groups and aromatic protons, more catechol groups, and 

more aliphatic protons (Swan 1966). 

Compounds that have been extracted from western redcedar bark 

i ncl u de: 

arachidic acid (Fraser and Swan 

aspartic acid (Swan 1963b) 

campesterol (Fraser and Swan 1978) 

catechin (Swan 1963b) 

D-fructose (Swan 1963b) 

D-glucose (Swan 1963b) 

diethyl octadecanedioate (Swan 

docosanoic acid (Fraser and Swan 

eicosanoic acid (Fraser and Swan 

epicatechin (Swan 1963b) 

ethyl 18- h yd roxyst earat e (Swan 

ferulic acid (Swan 1968) 

isopimaric acid (Fraser and Swan 

leucocyanidins B and C (Swan 

myristic acid (Fraser and Swan 1978) 

1 9-nor i sop i ma raS( 1 4), 1 5-d ien-3-one 

norditerpene alcohols (Quon and 

oleic acid (Fraser and Swan 1978) 

palmitic acid (Fraser and Swan 1978) 

phydroxyphenylpyruvic acid 

shikimic acid (Swan 1963b) 

stearic acid (Fraser and Swan 1978) 

sucrose (Swan 1963b) 

tannins, oils, and waxes (Smith and 

taxifolin glucoside (Hergert and 

terpinen-4-01 (Fraser and Swan 1978) 

tetracosanoic acid (Fraser and Swan 

thujone (Fraser and Swan 1978) 

xanot hoperol (Fraser and Swan 

1978) 

1968) 

1978) 

1978) 

1968 

1978) 

1963 b) 

(Fraser and Swan 1973) 

Swan 1969) 

(Swan 1963b) 

Kurth 1953) 

Goldschmid (1958) 

1978) 

1978) 

When Smith and Kurth (1953) analyzed several western redcedar 

trees near Oakridge, Oregon, they 

found that extractive contents of 

the bark were higher in treetops 

than in butt logs, rangingfrom 18 to 

29 percent. In contrast, calcium 

content of western redcedar bark 

Increases with distance from 

the treetop (Webber 1973). 

15 
Wood 

Stem wood made up 57 to 73 percent of the aboveground weight of 

the western redcedar trees 

measured by Smith and DeBell 

(1973) and 70 percent of the two 

redcedars measured by Grier and 

Logan (1977). The wood is coarse 

and straight grained with a 

characteristic sweet odor and faint 

bitter taste (Brown et al. 1949, 

lsenberg 1951, Forest Products 

Laboratory 1955). The green heartwood has an average moisture content in North America of 58 percent 

- about the same as the moisture 

content in the heartwoods of 

western larch, western white pine, 

Pacific silver fir, Engelmann spruce, 

and Port-Orford-cedar (see Forest 

Products Laboratory 1955). Western 

redcedar heartwood grown in New 

Zealand is very wet in many trees, 

however, and heartwood moisture 

content up to 298 percent has been 

recorded there (Harris and Kripas 

1959). The average moisture content 

of green redcedar sapwood in North 

America is higher than that of any 

other conifer - 249 percent (see 

Forest Products Laboratory 1955). 

North American western redcedar 

wood weighs 0.37 to 0.38 gkm3 (23 

to 24 Ib/ft3) when air dried, 0.31 to 

0.34 gkm3 (19.5 to 21.0 Ib/ft3) when 

ovendried (Desch 1948, lsenberg 

1951, Forest Products Laboratory 

1955, Higgins 1957, Smith and 

DeBell 1973). Weight per unit volume 

(density) of western redcedar wood 

varies with its position in the tree, 

increasing with height and decreasing from pith to cambium (Wellwood 

and Jurazs 1968, Okkonen et al. 

1972). Wood density also varies with 

geographic location and site. 

Western redcedar in Montana and 

Idaho is less dense than all other 

western conifer woods except that 

of subalpine fir (see Brown et al. 

1977). Densities of commercial 

redcedar wood are similar in Oregon 

and British Columbia - 55 percent 

and 56 percent that of Douglas-fir. 

The “scrub” redcedars of British 

Columbia have denser wood, however - 71 percent of Douglas-fir 

density (Wethern 1959). A survey of 

densities of western woods (Maeglin 

and Wahlgren 1972) showed great 

variation, with average specific 

gravities of western redcedar ranging from 0.318 in western Washington to 0.357 in Montana. Western 

redcedar wood grown in Germany is 

denser (0.37 g/cm3) than that grown 

in North America (see Volkert 1956). 

The German values decreased as annual ring widths increased - from 

0.4 gkm3 with 2-mm rings to about 

0.28 g/cm3 with 8-mm rings. 

Annual growth rings are distinct in 

western redcedar. Transition from 

springwood to summerwood within 

each annual ring is more or less 

abrupt, and the summerwood is narrow and hard (Brown et ai. 1949, 

lsenberg 1951, Forest Products 

Laboratory 1955). Resin canals are 

absent. Metatracheal parenchyma is 

present, but very variable in distribution. Rays are uniseriate and 1 to 

12+ cells high, with some gummy 

infiltration of the ray cells (Brown et 

al. 1949, Johnston 1951). Ray 

tracheids are occasionally found on 

the upper and lower margins (Brown 

et al. 1949, Kobayashi 1956). 

Tracheids have one to two rows of 

bordered pits on the radial walls 

(Brown et al. 1949). The membranes 

of these bordered pits do not 

possess a torus, but consist of 

numerous, closely packed strands 

(Krahmer and Cote 1963). 

Average tracheid diameter of 

western redcedar decreases with increased latitude, altitude, and tree 

age in Idaho (Crooks 1964). Redcedar tracheids in British Columbia 

are shortest near the stump. They 

reach maximum length about 

midheight in the tree and decrease 

slightly thereafter (Wellwood and 

Jurazs 1968). Wellwood and Jurazs 

found that tracheid length increased 

from the pith outward in redcedar 

wood. When the wood is macerated 

to make kraft pulp, western redcedar 

fibers average shorter (2.05 mm) 

than either western hemlock (2.21 

mm) or Douglas-fir (2.62 mm) fibers 

(Graff and lsenberg 1950). Summerwood fibers of western redcedar are 

unique in that increasing tensile 

strength is associated with a 

decreasing Young’s modulus (Jayne 

1960). 

Other stress limits and strength 

properties of western redcedar wood 

are listed by Newlin and Wilson 

(1917), the West Coast Lumber Trade 

Extension Bureau (1927), the Forest 

Products Laboratory (1955, 1963), 

and Bendtsen (1972). Their data 

show that the ends of western 

redcedar are harder and more difficult to crush than the ends of 

western white pine and sugar pine, 

but its sides are softer and easier to 

crush. Redcedar shear strength is 

low. Volumetric shrinkage and thermal conductivity are also low, 

however; western redcedar has the 

lowest volumetric shrinkage listed 

by Higgins (1957) and the lowest 

thermal conductivity of any softwood listed by the Forest Products 

Laboratory (1955). Its thermal 

emissivity is approximately 0.91 

(Owens 1964). The low tangential 

shrinkage of redcedar seems to be 

the result of a low summerwood 

percentage in the annual rings, plus 

relatively low shrinkage of both 

springwood and summerwood 

(Erickson 1955). Its longitudinal 

shrinkage, though low, is greater 

than those of western hemlock and 

the true firs (Espenas 1974). 

Western redcedar is a soft, stable, 

weak wood that splits easily and is 

not very tough. Toughness is increased by extracting extraneous 

compounds with an alcohol-benzene 

mixture (Raczkowski 1968, Lawniczak and Raczkowski 1970). 

Toughness and strength seem to 

vary with redcedar wood color. Dark 

brown heartwood is less tough, 

softer, and weaker than lighter colored heartwood (Findlay and Pettifor 

1941). This dark brown heartwood 

usually occurs near the center of the 

tree and is surrounded by a narrower red-stained layer inside an 

16 
outer zone of straw-colored heartwood (van der Kamp 1975). Redcedar 

sapwood is white and narrow, 

generally 2.5 cm (1 in) or less wide 

(Lutz 1972). It is wider than western 

larch sapwood, narrower than the 

sapwoods of Engelmann spruce, 

Douglas-fir, lodgepole pine, or 

ponderosa pine (Lassen and Okkonen 1969). Krahmer and Cote 

(1963) found the air-permeability 

ratio of early sapwood to late heartwood to be 6.5 in redcedar - lower 

than in Douglas-fir or western 

hemlock. Redcedar heartwood pH 

(3.0 to 3.4) is lower than sapwood 

pH (4.1 to 4.7) (van der Kamp 1975). 

Although western redcedar has a 

lower pH than most species (see 

Farmer 1962), the wood acts as a pH 

buffer when suspended in water 

(Carroll et al. 1973). 

The identification of heartwood and 

sapwood is usually relatively easy 

for western redcedar. Nevertheless, 

application of perchloric acid, 

Benedict’s solution, Fehling’s solution, or ammonium bichromate may 

be useful in difficult cases (Brown 

and Eades 1948, Eades 1958). The 

usual heartwood-sapwood orientation is absent in some southeastern 

British Columbia redcedars, where a 

target-shaped pattern of alternate 

concentric bands of light- and darkcolored wood occurs (MacLean and 

Gardner 1956b). The dark heartwood 

bands are rich in natural preservatives. Very dark oil or resin streaks 

are even richer in preservatives 

when they occasionally occur in 

western redcedar heartwood (Gardner 1963). 

Natural preservatives comprise one 

of the most important and interesting characteristics of western 

redcedar. About 10 percent of the 

total heartwood consists of extractives (Gardner 1963), and up to 23 

percent extractive content has been 

found in some portions (MacLean 

and Gardner 1956a). Indeed, 30 to 50 

percent extractive content sometimes occurs in the resin streaks 

(Gardner 1963). 

A complete list of the many organic 

compounds in redcedar wood would 

be long. The six most important 

compounds isolated from volatile 

oils and their approximate percentages in butt heartwood are listed 

below (see Anderson and Gripenberg 

1948; Erdtman and Gripenberg 

1948a; Rennerfelt 1948; Gardner and 

Barton 1958a, 1958b; Roff and Whittaker 1959; Wethern 1959; Lyr 1961; 

and Gardner 1963): 

a-t h u japl ic i n 0.01 percent 

p t h ujapl ici n 0.30 percent 

y-t hujapl ici n 0.20 percent 

p-thujaplicinol (7-hydroxy 

4-isopropylt ropolone) 0.07 percent 

thujic acid ’ 0.08 percent 

methyl t hujate 0.17 percent 

Polyphenolic lignans may not be as 

important, but they make up the major portion of the heartwood extractives (see MacLean 1970). Eleven of 

these lignans have been identified 

and described (Gardner et al. 1960, 

1966; MacDonald and Swan 1970; 

MacDonald and Barton 1973; Kirbach and Chow 1976): thujaplicatin, 

di hydroxy t hujapl icat i n, t hujapl icat i n 

methyl ether, hydroxy thujaplicatin 

methyl ether, di hydroxy t hujaplicatin 

methyl ether, y-thujaplicatene, plicatic acid, plicatin, plicatinapht halene, plicat inapht hol, and 

paplopl icat itoxin. 

Thujaplicatin and the thujaplicatin 

methyl ethers are also present in 

much smaller concentrations within 

the sapwood. They build up slowly 

there, then increase dramatically at 

the sapwood-heartwood boundary 

(Hillis 1968, Swan et al. 1969, 

MacLean 1970). Treatment with enzyme inhibitors may increase the 

amounts of thujaplicatin, thujaplicatin methyl ethers, and 

p-sitosterol produced in sapwood 

(see Swan 1971). 

Other western redcedar wood constit uen t s i nc I ud e p-d o I a b r i n (Gard ner 

and Barton 1958a, Gardner 1963), 

nezukone (Hirose and Nakatsuka 

1967), cumic acid (Barton and MacDonald 1971), unnamed soluble and 

insoluble phenols (Barton and Gardner 1954, Krueger 1968), and various 

hemicelluloses (Lewis 1950, Hamilton and Partlow 1958). Western 

redcedar hemicel I u loses are si mi lar 

to those of other conifers, except 

that the xylan contains a lower 

percentage of L-arabinose (Dutton 

and Funnel1 1973). Western redcedar 

wood has a high lignin content 

(Lewis 1950) - higher than the 

woods of western hemlock, Douglasfir, and Engelmann spruce (Wilson 

et al. 1960). More nonreducing 

sugars than reducing sugars are 

present in the sapwood (Radwan 

1969). 

Thujaplicin and water-soluble phenol 

increase in redcedar heartwood with 

distance from the pith, decrease 

with height (MacLean and Gardner 

1956a, Tickle 1963). Calcium and 

potassium in the wood increase with 

height (see Webber 1973). 

Soluble phenols apparently leach 

out of redcedar wood when fresh 

logs are stored in water. Kiser and 

Griel related the periodic absence of 

plankton from millponds to the 

presence of freshly cut western 

redcedar logs in those p0nds.Y Their 

subsequent laboratory experiments 

indicated that steam-distilled redcedar oil from freshly cut old-growth 

sawdust was more toxic to 

copepods and cladocerans than 

‘either formalin or chloral hydrate. 

Wnpublished report, “The effect of red 

cedar oil on zooplankton organisms,” by 

R.W. Kiser and J.V. Griel. 1956. On file, 

Centralia Junior College, Centralia, 

Washington. 

17 
Products 

The thujaplicins, dolabrin, and thujaplicinol (“tropolones”) are toxic to 

coho salmon fry (Peters 1974, Peters 

et al. 1976) and guppies (Erdtman 

and Gripenberg 1948b). They are 

also largely responsible for the high 

natural durability of western redcedar wood (Barton 1973b). Variation 

in tropolone content therefore leads 

to variation in wood durability. Some 

cedar roofs last 50 years, for example, but others decay in less than 10 

(Roff et al. 1962). The different 

moisture conditions associated with 

steep and flat roof pitches probably 

also contribute to these differences. 

Under similar conditions, redcedar 

wood deteriorates more slowly than 

the woods of western hemlock, 

Pacific silver fir, Sitka spruce, or 

Douglas-fir (Boyce 1929, Buchanan 

and Englerth 1940). 

Cartwright (1941) and Englerth and 

Scheffer (1954) found the most 

durable western redcedar to be that 

nearest the base of the tree in the 

outer heartwood. The wood in large 

western redcedar logs is often exceedingly resistant to decay, and it 

sometimes remains sound after hundreds of years on the ground (see 

West Coast Lumber Trade Extension 

Bureau 1927). The fire resistance of 

western redcedar is poor (see Hall 

and Dell 1970), and moist heat 

reduces its decay resistance (Scheffer and Eslyn 1961). 

Uses and Properties 

Western redcedar products have 

been important since prehistoric 

times. North American Indians, particularly tribes living along the 

coasts of Washington and British 

Columbia, used redcedar in many 

ways. Large logs were carved into 

totem poles and hollowed out to 

make huge ocean-going canoes. The 

redcedar logs were also split into 

wide planks used in building large 

timber frame structures that were 

often 15 m (50 ft) or more square 

(Vastokas 1969). Recent excavations 

of buried structures made by Indians 

have uncovered redcedar planks 

thought to be 6,000 to 10,000 years 

old (Sharpe 1974). Bark from young 

trees was used by the Indians to 

make baskets, ropes, blankets, 

mats, clothing, and thatch (see 

Sargent 1933, Bowers 1956, 

Dallimore and Jackson 1967, Bolsinger 1979). The flexible young 

branches were also used in making 

baskets. Thin twigs were woven into 

whaling ropes, and thicker ones 

were used for arrows (Edlin 1968). 

The roots were used for fishhooks 

(Dallimore and Jackson 1967). 

Modern society also uses western 

redcedar in a variety of products. 

The wood is valued for canoe and 

boat construction, and redcedar is 

still being used to build timber 

frame structures - as exterior 

siding, shingles, sashes, doors, window frames, and interior finish 

(Forest Products Laboratory 1955, 

Wood 1959). In addition, western 

redcedar is used in utility poles, 

fenceposts, piling, paper pulp, 

clothes closets and chests, caskets, 

crates, boxes, beehives, rain gutters, 

and fish-trap floats (Butler 1949, 

Viereck and Little 1972, Sharpe 

1974). A complete list would include 

many other products, for the wood 

is suitable for many uses. 

Western redcedar wood is nonresinous, light, and easy to work 

(Forest Products Laboratory 1955, 

Wood 1959). It has exceptional 

dimensional stability and is a good 

thermal insulator (Forest Products 

Laboratory 1955, Tickle 1963). Redcedar wood glues easily, particularly 

with nonresin glues (Forest Products 

Laboratory 1955). Although naturally 

durable, it is difficult to impregnate 

with artificial preservatives - even 

by pressure processes (Titniuss 

1965). 

The ease of splitting redcedar is an 

advantage in the manufacture of 

handsplit shakes, but a disadvantage when trees are felled on rough 

hills and yarded with heavy machinery. Breakage, splitting, and 

shattering are often severe (McBride 

1959). The wood is weak when used 

as a beam or post and low in shock 

resistance (Forest Products Laboratory 1955). The low density of redcedar was associated with poor fire 

resistance in the British standard 

fire-propagation test (Hall and Dell 

1970). It is a soft wood that is extremely sensitive to marring (Packee 

1976). The density and hardness of 

western redcedar can be increased 

threefold by using heat and pressure, without the addition of chemicals, but this is only a laboratory 

procedure of no commercial importance (Research News, Ottawa 

1962a). 

Western redcedar is one of the 

poorest woods for nail- and screwholding capacity. It is also poor for 

bolt-holding and is one of the 

weakest woods for withstanding 

connector loads (see Forest Products Laboratory 1955, Hokhold 1965). 

Special ring-shanked nails improve 

the nail-holding capacity of redcedar 

(Lee and Lord 1960), and increasing 

the screw lengths by 0.6 cm (114 in) 

improves its screw-holding properties enough to equal those of western hemlock, Scotch pine, and Norway spruce (British Columbia 

Lumber Manufacturers Association, 

n.d.) 

Dry western redcedar takes and 

holds stains, paints, enamels, and 

clear finishes very well (West Coast 

18 
Lumber Trade Extension Bureau 

1927, Wood 1959, Jones 1966). It 

ranks with redwood as the best 

paint substrate available in North 

American woods (Gardner 1963). 

Lack of extreme differentiation between springwood and summerwood, plus low summerwood swelling and the resulting lack of raised 

grain, seem to be responsible (see 

Brown 1957, MacLean 1970). Blistering is serious where free water (not 

just water vapor) is present behind 

the paint film in western redcedar, 

however; more serious than in 

Douglas-fir, Alaska-cedar, white 

pine, red pine, or spruce (Veer and 

King 1963). Extractive globules 

became concentrated on the paint 

surface in the 100-percent humidity 

maintained by Veer and King. Extractive bleedthrough can be a problem (Forest Products Laboratory 

1966, MacLean 1970). 

One of the best clear finishes for 

western redcedar wood is a tung oil 

modified, phenolformaldehyde-resinbased varnish (Oliver 1957). The best 

pigmented, penetrating stain seems 

to be the Forest Products Laboratory natural finish (60 percent 

linseed oil, 5 percent pentachlorophenol, 10 percent pigment, 0.3 percent zinc stearate, 1.0 percent wax, 

and 3.7 percent volatiles); the best 

water-soluble inorganic salt finishes 

contain acid copper chromate, 

cbromated copper arsenate, or 

copper-pentachlorophenol (Grantham et al. 1976). When left unfinished, western redcedar weathers 

gray wood 1959) and resists decay, 

but erodes appreciably faster than 

redwood, Douglas-fir, Engelmann 

spruce, or ponderosa pine (Feist and 

Mraz 1978). Both western redcedar 

and redwood weathered better than 

Monterey pine, alpine-ash, Brisbane 

boxwood, or King-Wil I iam-pi ne in 

Australia (Woodhead 1969). Redcedar wood is quite resistant to corrosion by hydrochloric acid but is 

less suitable than baldcypress or 

longleaf pine for use in contact with 

acids (American Wood Preservers 

Association 1946). 

The many uses and excellent properties of western redcedar products 

have increased the demand for them 

in recent years. This increasing demand has been accompanied by accelerating price increases. Both consumption rates and prices have increased more rapidly for western 

redcedar products than for products 

of most other west coast woods 

(Bolsinger 1979). Western redcedar 

and Alaska-cedar commanded 

average round-log values higher 

than any other Alaska tree species 

in 1971 (Farr and LaBau 1971). 

In western Washington and northwestern Oregon, the average price 

paid for all western redcedar logs increased from $57.30 per thousand 

board feet in 1965 to $320.80 per 

thousand board feet in 1977 - an 

average annual increase of 15.4 percent compared with average annual 

price increases of about 12 percent 

for Douglas-fir and western hemlock 

during the same period (Bolsinger 

1979). The accelerating nature of 

these price increases is emphasized 

by Ruderman's (1978) calculations 

for 1975-77; average annual increases in log price were 35.1 percent for western redcedar, 20.0 percent for Douglas-fir saw logs, and 

13.2 percent for western hemlock. 

As the estimated annual harvest of 

western redcedar in the United 

States for 1975 to 1976 was 950 

million board feet (Bolsinger 1979), 

such price increases represent very 

large sums spent for redcedar products. 

Accelerating price increases and an 

increasing demand for redcedar 

products may stimulate greater use 

of defective western redcedars Ii ke 

those found in the extensive stands 

of decadent cedar and hemlock in 

interior British Columbia. Dobie 

(1976) concluded that rehabilitation 

of these decadent stands could be 

profitable only at very low discount 

rates for short rotations on good 

and medium sites, but subsequent 

price increases may provide 

economic alternatives. 

Lumber I 

Lumber was the chief western redcedar product in Oregon, Montana, 

and Idaho in 1976 (Bolsinger 1979). 

Most redcedar logs used for lumber 

manufacture are acceptable in 

terms of eccentricity, sweep, taper, 

and shake (see Packee 1976). 

Redcedar lumber cut from these 

logs is easy to kiln dry, but boards 

from the butt log (Desch 1948) and 

thick planks (Forest Products 

Research Board 1950a) sometimes 

collapse during drving The cell walls 

are distorted or obliterated, and 

redcedar lumber does not recover 

after collapsing (Tiemann 1941). 

Predicting collapse from the appearance of a log is difficult or impossible, but collapse is associated 

with higher than normal extractive 

content (Meyer and Barton 1971, 

Barton 1975). Most redcedar logs 

subject to collapse seem to come 

from low or swampy ground 

(Guernsey 1951). Guernsey observed 

that heavy boards were more likely 

to collapse than light ones. He 

recommended air drying before kiln 

drying or, if this is impossible, initial 

kiln temperatures that do not exceed 49°C (120°F). 

Kiln temperatures above 100 "C 

(212°F) with three to six times 

shorter drying times have been 

tested, but they resulted in nonuniform moisture content and a 

5-percent loss of bending strength in 

western redcedar (Ladell 1953). Less 

severe,' moderately accelerated drying schedules can be successfully 

used with lightweight boards of less 

'than 45-percent moisture content 

(Salamon and Hejjas 1971). Kiln drying does not destroy the heartwood 

extracts of redcedar, but it makes 

them more soluble (Sowder 1927). 

Kiln corrosion should be considered 

when western redcedar is dried, 

because the thujaplicins are steamdistillable; they sometimes condense on metal kiln parts and corrode them (Barton 1972). 

I 

19 
Extractive-caused metal corrosion 

occurs even without the high 

temperatures associated with kiln 

drying. The zinc and lead used in 

roof gutters and valleys are sometimes corroded by rainwater extracts 

from western redcedar shingles or 

shakes (Forest Products Research 

Board 1950b). Iron, steel, copper, 

and brass fasteners (such as nails, 

screws, hinges) often corrode when 

in contact with redcedar lumber (see 

Campbell and Packman 1944, 

Farmer 1962, Titmuss 1965). The 

carbide-tipped saws and knives used 

in lumber manufacture also are corroded, dulling much sooner when 

used on unseasoned western redcedar than when used on other 

woods (Kirbach and Chow 1976). 

Recommended remedies include 

substituting another metal for the 

cobalt in tungsten carbide and using 

aluminum or stainless steel nails, 

screws, and fittings (Research 

News, Ottawa 1962b). 

Where iumber is used under moist 

conditions, as in water-cooling 

towers, western redcedar seems to 

be less suitable than redwood (see 

Western Australia Forests Department 1961). Nevertheless, untreated 

redcedar lumber had a service life of 

about 18 years in Canadian cooling 

towers (Roff 1964). When waterrepellent treatments were applied to 

western redcedar, waxes and wax 

solutions gave the most durable 

results (Gray and Wheeler 1959). 

Western redcedar responded better 

than eastern redcedar or baldcypress to waxing and staining 

treatments used in the preparation 

of pencil slats (Greaves and Harkom 

1 949). 

Redcedar is the most important 

western species used for siding in 

the United States and Canada (Panshin and deZeeuw 1970), and it 

shows promise as a homegrown 

lumber species in Great Britain 

(Priest 1974). It is suitable for pattern making in foundries (Hale 1954). 

Redcedar makes excellent horticultural boxes (Moore and Bryan 1946) 

and is used in greenhouse construction (Syrach Larsen 1943). Western 

redcedar is unsuitable for apple 

boxes, however; the apples absorb 

volatiles from the wood and spoil 

(Ministry of Agriculture, Belfast, n.d.; 

Colhoun et at. 1961; Colhoun and 

Park 1963; Loughnane and Gallagher 

1963). 

Shakes and Shingles 

Shakes and shingles are the chief 

western redcedar products in Washington, and British Columbia exported 3,294,000 squares in 1978.1 

Recent increases in shake and 

shingle production have been 

greater than the production increases in other redcedar products 

(Bolsinger 1979). Even before those 

increases, more than 95 percent of 

all wooden shingles manufactured 

in the United States were made from 

western redcedar (Brown and Panshin 1940). Attractive appearance, 

durability, lightness, and superior insulation probably are responsible for 

the popularity of redcedar as a roofing material. The insulating properties of 2.54 cm (1 in) of western 

redcedar wood are equal to 30 cm 

(12 in) of concrete or 19 cm (7.5 in) 

of brick or clay tile (O’Hea 1947). 

Three types of redcedar shakes are 

manufactured: Straight split, taper 

split, and handsplit-resawn. All 

come in random widths of 10 to 30 

cm (4 to 14 in). Lengths range from 

46 to 81 cm (18 to 32 in), but the 

61-cm (24-in) length is most common 

‘This statistic was obtained from the 

Council of Forest Industries of British 

Columbia, Vancouver. A “square” is the 

amount of shingles or shakes required to 

cover an area of 9.29 m2 (100 ft’), exclusive of overlap. 

(The Lumberman 1957). St raig ht-spli t 

and taper-split shakes are both 

handsplit from redcedar blocks, but 

the blocks are reversed every other 

time for taper-split shakes. Handspl it-resawn shakes, which account 

for most of the shake production, 

have a coarse-textured split surface 

on one side and a smooth sawn surface on the reverse side (Munger 

1970). 

Only old, slow-growing, straightgrained, relatively knot-free western 

redcedar trees seem to be suitable 

for shake manufacture. Good shake 

material has 35 to 50 annual rings 

per inch (14 to 20 rings per cm). At 

least 245 years are required to produce a tree of suitable size for such 

material, and the shake industry is 

supported by redcedar trees that are 

500 to 1,500 years old (Munger 1970). 

Such trees probably constitute a 

nonrenewable resource when considered in the scale of human time 

(see Munger 1970, Mitson and 

Holman 1975). 

Younger trees may be suitable for 

redcedar shingles (Packee 1976). The 

two types of western redcedar 

shingles are slash grain and edge 

grain. Edge-grain shingles do not 

curl and are more durable (O’Hea 

1947). Although untreated redcedar 

shingles may last for 25 years in 

Pennsylvania (Fergusson 1938) and 

50 years in Washington (see Grondal 

1913), they are less durable than redwood shingles in the wetter parts of 

Honolulu (Skolmen 1968). Leaching 

of the water-soluble heartwood extractives in wet conditions may be 

responsible (see Cserjesi 1976), but 

the low pitch of modern roofs also 

reduces durabi I ity. 

Pressure impregnation with copper, 

chromium, and arsenic preservatives 

improves the durability of redcedar 

shingles (Smith 1964b). Impregnation 

with leach-resistant fire retardants 

makes the shingles more fire resistant (St. Clair 1969, Holmes 1971, 

Juneja 1972). Amino-resin-forming 

compounds are effective retardants 

(King and Juneja 1974). 

20 
High-temperature kiln-drying schedules can be used to bring unbundled 

western redcedar shingles from 

green to shipping weight in less 

than 2 hours (see Salamon 1960). 

Shingle durability is not appreciably 

affected by these high-temperature 

schedules (MacDonald and MacLean 

1965). 

Poles and Piling 

Good form, large size, light shipping 

weight, easy climbing-spur penetration, and durability make western 

redcedar an excellent species for 

pole production, but it has a tendency to crush when used as piling 

(Brown and Panshin 1940). Redcedar 

poles taper more than southern pine 

or Douglas-fir poles (Bohannan et al. 

1974). They are remarkably consistent in strength, however, showing 

no significant differences between 

geographic locations, elevations, or 

seasoning treat men ts (McGowan 

and Smith 1965). 

Western redcedar poles constitute a 

plentiful renewable resource in 

British Columbia. Anderson (1961) 

estimated a provincial supply of 

about 121 million poles. Without 

considering annual growth, he 

forecast a pole supply of 300 years 

at the 1961 cutting rate of 400,000 

poles per year. Approximately 

200,000 poles were cut each year in 

the United States, which consumed 

about 400,000 redcedar poles annually (Anderson 1961). 

Average-size western redcedar poles 

with sapwood less than 2.54 cm (1 

in) thick should last about 12 to 17 

years without treatment (Forest 

Products Laboratory 1955). More 

than half the untreated redcedar 

telephone poles on the Island of 

Hawaii were still serviceable after 20 

years, however (Boone 1965). When 

in contact with the ground, they 

have a service life proportional to 

their diameter, not their crosssectional area (Purslow 1962). 

The service life of redcedar poles 

has been increased through several 

preservative treatments. Spraying 

freshly peeled green poles with urea 

minimized the checking that sometimes occurs during drying (West 

Coast Lumberman 1941). The dry 

poles were pressure treated with 

creosote and creosote-coal tar solutions during the 1940’s (American 

Wood Preservers Association 1943, 

1944). Hot- and cold-bath treatments 

with creosote and pentachlorophenol were then tried (see Colley 

1946). Preservative penetration was 

often poor in western redcedar 

poles, however, and it varied with 

position and wood condition within 

a single pole (Jurazs and Wellwood 

1965). Fortunately, the portions with 

poorest penetrability seemed to 

have the highest extractive content 

and least need for preservative treatment. Nonpressure treatment - 

such as butt-soaking or soaking the 

entire length of the pole - is common now. Pressure treatments are 

less used - the redcedar poles tend 

to become oversaturated (Randall 

and Sutherland 1974). 

Redcedar poles are seldom retreated now, but several formerly 

used procedures for retreating inservice poles are of historical 

interest. One method was machineshaving the sapwood and subsequently soaking the shaved pole in 

creosote (Lyon 1939). A somewhat 

similar procedure was used on redcedar bridge piling. After removing 

soil from around the affected portion, decayed wood was scraped off 

and the piling treated with a gelatinous suspension of NaF dinitrophenol and potassium dichromate 

(Railway Track and Structures 1955). 

Aboveground sap rot in redcedar 

poles has been treated by spraying 

with a 10-percent solution of pentachlorophenol (Graham and Wright 

1959, Scheffer and Graham 1973). 

Green or wet western redcedar 

power poles - particularly wet 

poles that have been in saltwater - may have low electrical resistances 

that are potentially hazardous to 

line workers (see Katz and Miller 

1963, Breeze and Vitins 1965). 

Pulp 

The low density of western redcedar 

is the most serious handicap to its 

increased use in pulping (Wethern 

1959). Pulp is produced and sold by 

weight, but the logging and lumber 

industries work by volume. Because 

a given volume of western redcedar 

contains only 77 percent as much 

wood by weight as the same volume 

of western hemlock and only 66 percent as much as the equivalent 

volume of Douglas-fir, the redcedar 

produces less pulp (Wethern 1959). 

Low lignin and ex;. active contents 

are highly desirable for chemical 

pulping processes - but western 

redcedar wood has relatively high 

contents of both (see Packee 1976). 

The stringy redcedar bark is difficult 

to remove with standard debarking 

equipment. Chemical debarking with 

sodium arsenate has been tried successfully (DeMoisy 1952); ingrown 

bark is difficult to remove by any 

debarking technique, and it may 

create problems in some chemical 

pu I pi ng processes. Pi lot-plant 

studies indicated that redcedar bark 

could be processed satisfactorily, 

however, and even whole-log chipping was possible (Thomas and 

Davis 1974). 

The sulfate process is most frequently used to produce pulp from 

western redcedar. Yields are lower 

in sulfate than sulfite pulping, increasing the disadvantage of redcedar density mentioned earlier 

(Wethern 1959). The acidic constituents of western redcedar wood 

consume extra alkali, further reducing profits in a sulfate pulping 

operation (see Thomas and Davis 

1974). Redcedar extractives corrode 

the steel ordinarily used in digesters 

and recovery equipment, sometimes 

reducing digester life by 50 percent 

compared with digesters used for 

western hemlock or Douglas-fir 

21 
(Wethern 1959, Thomas and Davis 

1974). The life of evaporator tubes 

may be reduced by 80 percent (see 

Gardner 1963). Thujaplicins, a 

phenolic constituent, or both probably are responsible (British Columbia Lumberman 1953, MacLean and 

Gardner 1953a). Redcedar pulp 

drains poorly, sometimes restricting 

production even further (Thomas and 

Davis 1974). Its color constitutes a 

final handicap (Troxell 1954); redcedar pulp bleaches with difficulty 

(Isenberg 1951). 

Some handicaps of redcedar pulping 

have been turned into advantages by 

skillful manipulation of the sulfate 

process, and redcedar has some 

favorable pulping characteristics. 

For example, adding 3 to 5 percent 

sodium sulfide to the cooking liquor 

offsets the deleterious effects of 

high alkalinity and improves both 

the yield and strength of redcedar 

pulp (Christiansen et al. 1957). 

Western redcedar requires a shorter 

sulfate-process cooking time than 

other British Columbia species 

(Wilson et al. 1960). It has finer 

fibers than western hemlock, 

Douglas-fir, or southern pine and 

makes a dense sheet with good 

opacity (Murray and Thomas 1961). 

Indeed, bleaching sulfate pulp made 

from western redcedar sawdust 

yields a product with an opacity 

comparable to hardwood pulps 

(Proctor and Chow 1976). The fine 

fibers tend to be shorter than those 

in Douglas-fir pulp (Heinig and Simmonds 1948, Graff and Isenberg 

1950), but western redcedar pulp 

does not differ chemically from the 

sulfate pulps of Douglas-fir, western 

hemlock, black spruce, or loblolly 

pine (Lewis et al. 1950). 

Physically, redcedar pulp has 

several desirable attributes. Unlike 

Douglas-fir, western hemlock, or 

Pacific silver fir, western redcedar 

produces very good kraft (sulfate) 

pulp (see Packee 1976). This pulp 

has high bursting, folding, and tensile strengths that offset its low 

tearing strength (see Bray and Martin 1947, Holzer and Booth 1950, 

Wethern 1959, Wilson et al. 1960, 

Murray and Thomas 1961). Western 

redcedar pulp has a high specific 

surface area (Browning and Baker 

1950). Its cellulose characteristics 

are similar to those of western 

hemlock and loblolly pine pulps (see 

Clark 1950, Heuser et al. 1950). 

Sulfate pulp made from redcedar 

bark has lower bursting and tensile 

strengths, higher tearing strength 

than that made from wood (Thomas 

and Davis 1974). 

Although sulfite pulp yields are 

higher than sulfate (kraft) yields for 

western redcedar (see Packee 1976), 

redcedar requires a longer cooking 

time and more chemicals than 

western hemlock in the sulfite process. The resulting low-brightness 

cedar pulp drains poorly (Wethern 

1959). Redcedar sulfite pulp is dark 

and difficult to bleach (Isenberg 

1951), and the use of a bisulfite 

cooking liquor with a high magnesium content seems necessary (see 

Keller and McGovern 1945). The 

bursting strength of western 

redcedar sulfite pulp is relatively 

high in comparison with the‘sulfite 

pulps of other species. Its tear 

strength is relatively low (see Holzer 

and Booth 1950). 

Mechanical (ground wood) pu I pi ng 

processes are not practical for 

western redcedar (Wet hern 1959). 

The resulting product has very good 

strength and printing qualities but 

poor brightness (see Packee 1976). 

Semichemical redcedar pulps may 

be useful in making paperboard 

(McGovern et al. 1951). 

Veneer and Plywood 

Western redcedar is highly suitable 

for decorative face veneer, but unsuitable for the inner plies of 

decorative veneer or for use in container material (see Packee 1976). 

Packee rated redcedar veneer logs 

as excellent when assessed for 

freedom from reaction wood, resin 

or gum, and bark pockets. Redcedar 

logs were rated “acceptable” when 

assessed for freedom from decay, 

knots, and wet wood. 

Western redcedar plywood panels 

can be made by slicing the logs and 

cold pressing the resulting veneer 

(West Coast Lumberman 1946). 

Where hot pressing is used, high 

glue spreads and press temperatures of 270°F (132°C) or lower have 

been recommended to prevent 

blistering (Carstensen 1961). Although highly rated for decorative 

plywood (Lutz 1972), redcedar is too 

weak for construction grade structural plywood (Palka and Warreh 

1977). 

Waste Utilization 

Redcedar lumber, shake, and 

shingle manufacture produces tremendous quantities of waste material. Logging residue in some clearcut redcedar stands may average 

238 mVha (3,400 ftjlacre) (Howard 

1973). The residues produced annually from cedar sawmills in 

Oregon, Washington, and British 

Columbia were estimated to be 1 to 

1.5 million ovendry tons (907 to 1361 

million kilograms) in 1968 (Scroggins 

and Currier 1971). Annual residues 

from shake and shingle mills were 

estimated to be 700,000 ovendry 

tons (635 million kilograms). 

The average amounts of mill residues produced in western redcedar 

log processing are listed in table 5. 

Shake manufacture produces the 

least amount of waste, shingle 

manufacture the most. In shingle 

manufacture only a small portion of 

the original tree is marketed; slash 

and mill residues account for most 

of the original standing volume. 

Much of the mill residue is suitable 

for pulp production (Bray and Martin 

1947). It can also be used in fiberboard production if treated properly. 

Boards made from western redcedar 

bark alone tend to be unacceptably 

weak (see Schwartz 1949, Clermont 

and Schwartz 1948, Stewart and 

Butler 1968, Maloney 1973), but 

ozone treatment increases the 

22 
bark’s internal bond strength (Chow 

1977b) and the addition of 10 percent sulfite pulp or sulfite screenings makes bark boards stronger 

(British Columbia Lumberman 1948). 

Boards made from wood components of the residue were acceptably strong (King and Bender 1951, 

1952). Those made from sawdust, 

shingle tow (a stringy waste product 

resulting from shingle manufacture), 

or both were not (see Forest Products Laboratory, Canada 1949; King 

and Bender 1951, 1952). 

Of all west coast conifer sawdusts, 

that of western redcedar is the only 

one that can be made into high 

quality, opaque pulp comparable to 

the hardwood sulfate pulps used in 

high-quality papers (Proctor and 

Chow 1976). It can be differentiated 

from the sawdusts of Douglas-fir, 

western hemlock, true firs, and the 

spruces with a color test using 

chloroform and ferric chloride (Barton 1973a). Redcedar sawdust apparently decomposes more rapidly 

than Douglas-fir or western hemlock 

sawdust (see Bollen and Lu 1957). 

When not leached, it inhibits seed 

germination and seedling growth 

(Newton 1953) and damages 

Douglas-fir seedling roots (Krueger 

1968). Redcedar sawdust makes a 

satisfactory rooting medium, how 

ever, when it is leached to remove 

the water-soluble extractives and 

mixed 3:l with peat (Briggs 1973). 

Perhaps the most novel use of 

redcedar sawdust was as fill 

material where the trans-Canada 

highway crossed bogs and marshes 

(Southern Lumberman 1961). 

Shingle tow has been used since 

about 1915 to keep tree seedlings 

moist during shipment. Krueger 

(1963, 1968) studied its effects on 

seedling survival and growth. He 

found that the thujaplicin extractives present in shingle tow were 

damaging to Doug las-f ir seedlings 

but considered that the use of 

shingle tow was unlikely to cause 

heavy losses. 

Table 5 - Average amounts of mlll resldues produced In processing of 

western redcedar logs‘ 

Product 

Coarse 

residues 

Fine 

residues 

Total 

waste 

Lumber 

Shakes 

Shingles 

Percent of log volume 

37 

28 

18 19 

14 14 

14 47 61 

‘From McBride (1959), Gardner (1963), Scroggins and Currier (1971). 

Extractives 

Shingle tow, sawdust, and coarse 

residues are probably the best raw 

materials for producing most redcedar extractives (Wethern 1959). 

p- t h u j a p I i c i n acc u m u I at es i n 

digesters, evaporators, and kilns 

during redcedar processing, however, where it is readily available in 

commercially usable quantities 

(Trust and Coombs 1973). Potential 

uses of these extractives include insecticides, fungicides, antibiotics, 

chelating agents, catalysts, and perfumes (Wet hern 1959). 

Cedar leaf oil has been used in perfumes, insecticides, medicinal preparations, veterinary soaps, shoe 

polishes, and office deodorants 

(Forestry Abstracts 1965, Barton 

1973b). It is a strongly scented, 

viscous liquid containing thujone, 

pinene, borneol, and borneol esters 

(Cochrane 1951, Bender 1963). 

Cochrane and Bender described the 

distillation procedure used to obtain 

this product. Steam extraction of 

freshly cut western redcedar leaves 

yielded 2.5 percent oil, based on dry 

leaf weight (Cochrane 1951). 

Extractives probably were important 

in the successful production of fuel 

logs from wet redcedar sawdust 

(Gardner 1963). They were used to 

make a boiler-water additive that 

removed boiler scale and controlled 

foaming (British Columbia Lumberman 1951, McBride 1959). Watersoluble redcedar extractives have 

also been used in the electrolytic 

refining of lead (British Columbia 

Lumberman 1959). Even the lignin 

residue of Poria asiatica butt rot in 

western redcedar has been used - 

as a filler and extender in plywood 

glues (MacLean and Gardner 1953b). 

Most of the extractives in western 

redcedar heartwood are formed from 

precursors at the sapwoodlheartwood boundary (Swan et al. 1969). 

For example, nezukone is converted 

to thujaplicin at this boundary by 

hydroxylation of the tropone ring 

(Swan and Jiang 1970). The formation of different amounts of each extractive in older heartwood may be 

the result of changes in metabolism 

(more hydroxylation, less methylation) with aging (Hillis 1968). 

23 
Medical Aspects 

Although less potent than sodiumpenicillin G and tetracycline hydrochloride, a-thujaplicin has been 

shown to inhibit the growth of a 

wide variety of bacterial species 

(Trust and Coombs 1973). It loses its 

antibacterial potency after irradiation by laboratory lighting (Coombs 

and Trust 1973). 

Other western redcedar extractives 

seem to be more stable than 

a-thujaplicin. Southam (1946) found 

that water extract of redcedar heartwood inhibited the growth of bac- . teria and fungi even after the extract 

was boiled. It was inactivated by 

blood, serum, and cysteine. Large 

doses of redcedar extract did not 

cause death or illness in mice, and 

no in vivo activity against infection 

was demonstrated (Southam 1946). 

Both p- and y-thujaplicins exert a 

combination of stimulant and 

depressant actions on the mammalian central nervous system, but 

the depressant component appears 

to be more predominant in 

a-t hujapl icin (Hal I iday 1959). 

Western redcedar allergies are frequently mentioned in the literature. 

Woods workers who handle redcedar sometimes develop dermatitis, 

conjunctivitis, or both (Ishizaki et al. 

1971a, 1971b; Mitchell and ChanYeung 1974). Most of the dermatitis 

seems to result from contact with 

lichens and liverworts on the logs, 

however, and contact dermatitis 

from the redcedar itself is rare 

(Mitchell and Chan-Yeung 1974). 

Where dermatitis was caused by exposure to redcedar heartwood in a 

mi I I, y-t hujapl ici n and 7-hydroxyisopropyltropolone appeared to be 

allergenic (Bleumink et al. 1973). 

Allergic mi I Iworkers, carpenters, 

cabinet workers, construction 

workers, and wood carvers develop 

asthma or rhinitis after being exposed to western redcedar dust 

(Mitchell and Chan-Yeung 1974, 

Chan-Yeung and Grzybowski 1976). 

The allergy seems quite common 

(Gandevia 1970; lshizaki et al. 1971a, 

1971b; Shida et al. 1971; Mue et al. 

1975; Chan-Yeung 1977). Symptoms 

are delayed, but persistent - nocturnal coughing and asthma for 

days or weeks after exposure (see 

Milne and Gandevia 1969, Gandevia 

and Milne 1970, Mitchell 1970, ChanYeung et al. 1971). Plicatic acid 

probably causes these symptoms 

(Chan-Yeung 1973, Chan-Yeung et al. 

1973, Barton 1975). 

Western redcedars suffer little insect damage (Boyd 1959). Nevertheless, a considerable number of insects use redcedar as a host. 

Bark Beetles 

The western cedar bark beetle 

(Phloeosinus punctatus LeConte) is 

widespread in the native range of 

western redcedar (see Boyd 1959, 

Canada Department of Agriculture 

1959, Canada Department of Forestry 1960). Generally of little importance, it has been reported to kill 

trees sometimes (Furniss and 

Carolin 1977), but it usually occurs 

in felled or weakened trees (Isenberg 

1951). 

The redwood bark beetle (P. sequoiae Hopkins) is present on redcedars in coastal Oregon, Washington, British Columbia, and southeastern Alaska. In southeastern 

Alaska it is aggressive, attacking 

and killing western redcedar on poor 

sites (see Hard 1974, Furniss and 

Carolin 1977). P. thujae Perris attacks redcedars planted in the 

Netherlands (Doom 1964) and Germany (Kamp 1951). 

Wood Borers 

The most damaging redcedar wood 

borer seems to be Trachykele 

blondeli Marseul, a flat-headed borer 

whose larvae mine the heartwood, 

causing degrade and cull in trees 

cut for products that require sound 

wood (Keen 1952, Boyd 1959, Furniss and Carolin 1977). Another flatheaded borer, T. opulenta Fall, also 

may occur in western redcedar (see 

Keen 1952). 

Three round-headed borers mine the 

sapwood of native western redcedar: 

Atimia confusa Say (Furniss and 

Carolin 1977), Semanotus amethystinus LeConte (Boyd 1959, Furniss 

and Carolin 1977), and S. ligneus F. 

(Furniss and Carolin 1977). Ambrosia 

24 
beetles (Gnathotrichus sulcatus 

LeConte, Trypodendron cavifrons 

Mannerheim, and other Trypodendron species) also work in western 

redcedar sapwood - but they seem 

to prefer Douglas-fir, western 

hemlock, or grand fir wood (see 

Johnson 1958). 

The sapwood weevil Hexarthrum 

thujae Brown attacks overmature 

redcedar in British Columbia 

(Canada Department of Forestry 

1960, Brown 1966, Furniss and 

Carolin 1977). Another sapwood 

weevil, Rhyncolus brunneus Mannerheim, breeds in dead redcedar 

wood (see Keen 1952, Canada 

Department of Forestry 1960, Furniss and Carolin 1977.) Insects of a 

third sapwood weevil genus 

(Cossonus spp.) live in decaying 

western redcedar, causing little or 

no economic damage (Keen 1952). 

Other native western redcedar 

borers include a horntail, Urocerus 

albicornis F. (Furniss and Carolin 

1977) and Syntexis libocedrii 

Rohwer, a wood-boring sawfly (Westcott 1971, Middlekauff 1974). European wood borers also attack 

western redcedar. Xyloborus dispar 

F. (an ambrosia beetle) is found on 

western redcedars growing in Germany (von Hennig 1954), and 

Hylotrupes bajulus L. (the oldhouse 

borer) can develop in redcedar wood 

grown in Poland (Dominik 1966). 

Redcedar siding on several British 

schools was riddled with the prepupal burrow: of Ametastegia 

glabrata Fallen (a sawfly) after the 

wet summer of 1958 (Benson 1959). 

Defoliators 

Seven loopers feed on western redcedar foliage: 

Lam bdina f is cell aria lugubrosa 

Hulst (Boyd 1959, Canada Department of Fisheries and Forestry 1969, 

Canada Department of the Environment 1974) 

Melanolophia imitata Walker (Evans 

1962, Dawson 1970) 

Ectropis crepuscularia Denis & 

Schiffermuller (Canada Department 

of Fisheries and Forestry 1968, Furniss and Carolin 1977) 

Caripeta diwisata Walker (Furniss 

and Carolin 1977) 

Neoalcis californiaria Packard (Furniss and Carolin 1977) 

Nepytia phantasmaria Strecker (Furniss and Carolin 1977) 

Nepytia umbrosaria nigrovenaria 

Packard (Furniss and Carolin 1977) 

Lambdina fiscellaria lugubrosa, the 

western hemlock looper, is periodically destructive in coastal forests 

(Furniss and Carolin 1977). Its 

preferred host is western hemlock, 

but western redcedar is damaged 

when the loopers attack associated 

trees. Melanolophia imitata, the 

green striped forest looper, prefers 

humid areas (Furniss and Carolin 

1977), where infestations sometimes 

cause serious defoliation of western 

redcedar and western hemlock 

(Dawson 1970). The saddleback 

looper, Ectropis crepuscularia, 

damaged redcedar trees in Alaska 

and British Columbia during 1951, 

1953, 1960, 1961, and 1969. The 

other loopers listed above do not 

damage western redcedar significantly (see Furniss and Carolin 

1977). 

Nine nonlooper lepidopteran species 

occur on western redcedar foliage: 

A rgyres thia cupressella W a I s i n g ha m 

(Keen 1952, Pettinger and Dolph 

1967) 

A. thuiella Packard (Van Frankenhuyzen 1974) 

Halisidota argentata Packard 

(Sellars-St. Clare 1968, Furniss and 

Carolin 1977) 

Protoboarmia porcelaria Gn. indicataria Walker (McGuffin 1943) 

Callophrys acumina ta Johnson 

(Johnson 1976) 

C. barryi Johnson (Johnson 1976) 

C. byrnei Johnson (Johnson 1976) 

C. plicataria Johnson (Johnson 1976) 

C. rosneri Johnson (Johnson 1976) 

A rgyres thia cupressella, the cypress 

tip moth, caused moderate redcedar 

defoliation on the Olympic Peninsula in 1966 (Pettinger and Dolph 

1967). A. thuiella damaged western 

redcedar hedges in Holland during 

the winter of 1971-72 (Van Frankenhuyzen 1974). An outbreak of silverspotted tiger moth (Halisidota argentata) occurred on southern Vancouver Island in 1954-55 (Furniss 

and Carolin 1977). The other species 

listed are not economically important. 

25 
Seed and Cone Insects 

Keen (1958) and Hedlin (1959) identified several insects of minor importance in western redcedar cones: 

Ptinus fur L. 

Microgramme arga Reitt. 

Eurytoma sp. 

Torymus sp. 

Amblymerus sp. 

Tetrastichus sp. 

L es to diplosis tax icon is Foot e 

The only major seed-damaging insect on redcedar seems to be a gall 

midge - Mayetiola (Phytophaga) 

thujae Hedlin (Hedlin 1959, 1964, 

1974; Furniss and Carolin 1977). 

Mayetiola is a common pest, sometimes infesting 100 percent of the 

cones (Keen 1958, Hedlin 1964) and 

seriously damaging western redcedar seeds in Oregon, Washington, 

and British Columbia (Furniss and 

Carolin 1977). 

Miscellaneous Insects 

Newly planted redcedar seedlings 

are sometimes damaged by the 

seedling weevi I Steremnius 

carinatus Mannerheim) on cutover 

areas in British Columbia (Koot 

1972), and another weevil (Hylobius 

abietis L.), attacks western redcedars in Poland (Ilmurzyhski 1968). 

A cicada (Melampsalta cingulata 

Fabricius) seriously damaged the 

western redcedars planted in 

Waimiha State Forest, New Zealand 

(Ranger 1945). 

Resistance of western redcedar 

wood to termites seems to vary with 

the termite species attacking it. 

Redcedar heartwood was not 

favored by Reticulitermes flavipes 

(Kollar) in a laboratory feeding test 

of 11 wood species (Carter and 

Smythe 1974). In feeding-choice 

tests of 21 commercial woods with 

R. virginicus Banks and Coptotermes formosanus Shiraki, however, western redcedar was among 

the least resistant woods tested 

(Mannesmann 1973). lncisitermes 

minor Hagen, the western drywood 

termite, preferred western redcedar 

heartwood to that of Douglas-fir, 

redwood, bald cypress, and PortOrford-cedar (see Rust and Reierson 

1977). It preferred redcedar sapwood 

to that of birch, Douglas-fir, oak, 

pine, redwood, or walnut. Another 

d r y w o o d t e r m i t e, C r yp to term e s 

brevis Walker, also preferred 

redcedar sapwood to the sapwood 

of Douglas-fir or southern yellow 

pine (Minnick et al. 1973). Redcedar 

heartwood lost much of its resistance to attack by Reticulitermes 

lucifugus Rossi after weathering in 

Germany (Arndt and Willeitner 1969). 

Extractives and Insects 

Loss of extractives probably was 

responsible for decreased termite 

resistance after weathering in the 

German study. Although western 

redcedar wood is not particularly 

termite resistant, a neutral fraction 

of the volatile oil extracted from it is 

very effective against termites 

(MacLean 1970). Arndt (1968) found 

Reticulitermes lucifugus and R. 

flavipes to be adversely affected by 

the neutral oil fraction, unaffected 

by a- and y- thujaplicins. lncisitermes minor preferred the extracts 

of walnut, Douglas-fir, sugar pine, 

redwood, and red oak to those of 

western redcedar - in almost 

reverse order to its preference for 

the woods from which these extracts were obtained (see Rust and 

Rei erson 1 977). The term it e- re pe I I en t 

oil in redcedar, though effective 

when extracted, probably is present 

in inadequate quantities to protect 

redcedar wood from attack by most 

termite species. 

Western redcedar sap probably is 

somewhat repellent to Pissodes 

strobi Peck, the Sitka spruce weevil. 

In laboratory bioassays, weevils 

preferred to feed on Sitka spruce 

sections soaked in water rather than 

on sections soaked in redcedar exudate (Vandersar and Borden 1977). 

Volatile extractives of western redcedar wood apparently affect the 

choices of scolytid beetles for logs 

- they choose other log species 

(see Chapman 1963). Another volatile derived from redcedar, the N, N, diethylamid of thujic acid, is a potent 

mosquito repellant that surpasses the 

activity of standard repellants (Hach 

and McDonald 1971). Methyl thujate 

has some toxicity to carpet beetles and 

clothes moths, and its presence in 

cedar shavings used as litter probably 

controls poultry mites (Gardner 1963). 

Wood extracts from western 

redcedar demonstrated juvenilehormonelike activity on pupae of 

Galleria mellonella L. (Mansingh et 

ai. 1970) and Tenebrio sp. (Barton et 

al. 1972). Similar activity occurred 

when larvae of the western tent 

caterpillar (Malacosoma californicum Packard pluviale Dyar) were 

treated with crude ether extracts of 

western redcedar (Wellington 1969). 

26 
Diseases 

Although Shaw (1973) lists 221 fungi 

that occur on western redcedar, the 

species is reputed to be less susceptible to pathological attacks than 

most of its associates (Boyd 1959). 

Nevert heless, most redcedars harbor 

pathogens. Redcedars live longer 

than their associates, and hollow 

old redcedar trees are common in 

the interior (see Daubenmire and 

Daubenmire 1968). Western redcedar 

is twice as defective as western 

hemlock and 20 times as defective 

as Sitka spruce in southeastern 

Alaska, where redcedars over 94-cm 

(37-in) d.b.h. average more than 50 

percent cull (Klein 1951). Smaller 

trees also are affected. Half the 

coastal redcedar trees in the southcentral portion of Vancouver Island 

have some decay by age 50; 100 percent have decay by age 450. In the 

interior, 80 percent of the redcedars 

are infected by age 150 and 100 percent have decay by age 290 (Buckland 1946). 

Seedling Diseases 

Western redcedar seedlings are 

seldom damaged by damping-off 

fungi (Hepting 1971). They are resistant to Phytophthora cactorum Leb. 

& Cohn (see Vaartaja 1957b) and 

often undamaged by Thelephora terrestris Ehr. growth (Hepting 1971). 

Where redcedar seedlings are dense 

enough to shade the ground, however, T. terrestris sometimes 

smothers them (Weir 1921). Some 

redcedar seedlings are killed by the 

brown-felt snow mold (Herpotrichia 

nigra Hartig) in the Rocky Mountains 

(Hepting 1971). Other fungi that 

sometimes damage western redcedar seedlings include Diaporthe 

lokoyae Funk, Seiridium cardinale 

(Wagener) Sutton & Gibson, 

Kabatina thujae Schneider & v. Arx, 

and Velutarina rufo-olivacea (Alb. & 

Schw. ex Fr.) Korf (Funk 1974). 

The major redcedar seedling disease 

- Didymascella (Keithia) thujina 

Durand - is a leaf blight that also 

occurs on older trees but is only 

serious on seedlings. When 

Didymascella reaches epidemic proportions, as much as 97 percent of 

the redcedar reproduction may be 

killed in its first season (Boyd 1959). 

Epidemics probably are rare in 

North America, however, and 

Didymascella is not as damaging 

there as it is in Europe (see Peace 

1955, Spegaard 1969). Infection is 

rarely observed on 1 st-year nursery 

seedlings in Europe, where major 

damage to nursery stock occurs during the 2d and 3d years (Spegaard 

1966, Forestry Commission, London 

1974). British attempts to avoid 

seedling damage by growing western redcedar in isolated nurseries 

(Peace 1955, 1958; Pawsey 1962b) 

succeeded at first, but eventually 

failed when those nurseries also 

became infected. Fortunately, 

diseased nursery seedlings sometimes recover after being planted 

out (see Keatinge 1948, Penistan 

1966). 

Effective control of Didymascella 

has been achieved by applying 

cycloheximide fungicides in British 

nurseries (Pawsey 1962a, 1965; 

Phillips 1962, 1964; Burdekin and 

Phillips 1971). Danish workers found 

that western redcedar cuttings are 

blight resistant (Spegaard 1954, 

1956a). 

Foliage Fungi 

The Didymascella leaf blight that attacks seedlings is the most important foliage disease of western redcedar. Blights caused by Coryneum 

thujinum Dearn. (Boyce 1961, Hepting 1971) and Lepteutypa cupressi 

(Nattrass, Booth, & Sutton) Swart 

(Canadian Forestry Service 1975) are 

much less important. 

P. peregrina Ell. & Mart. caused a 

severe dieback of western redcedar 

in India (Sharma et at. 1973) and 

Lophodermium juniperinum (Fr.) 

DeNot. has been found on redcedar 

in Australia (Stahl 1966). 

Chloroscypha seaveri (Re h m) Seav. 

has been associated with the death 

of weslern redcedar twigs (Ehrlich 

1942), but the twigs probably were 

killed by other organisms (Gremmen 

1963). Other fungi inhabiting dead or 

senescent redcedar foliage include 

Sphaerella canadensis, Ell. & Ev., 

Mycosphaerella thujae Petr., and 

Microthyrium thujae Dearn. (Hepting 

1971). Limacinia alaskensis (Sacc. & 

Scalia emend Barr.) causes a minor 

surface mold in cold regions (Hepting 1971). 

Root and Butt Rots 

Phellinus (Poria) weirii (M u rr.) 

Gilbertson is the principal root- and 

butt-rot fungus infecting western 

redcedar (Hepting 1971). Redcedars 

and Douglas-firs are the most frequent hosts of P. weirii (Smith 1978). 

The P. weirii hosted by western 

redcedar seems to be different from 

that hosted by Douglas-fir and other 

northwestern conifers, however. P. 

weirii sporophores are perennial on 

western redcedar, annual on other 

conifers (Buckland et al. 1954). Furthermore, nonredcedar isolates are 

less able to parasitize western 

redcedar than isolates from the 

redcedar race (Morrison 1969). Ectotrophic mycelia are nearly absent 

on redcedar roots infected with P. 

weirii (Wallis 1976), and western 

redcedar is quite resistant to the 

fungus (Wallis 1962, Wallis and 

Reynolds 1967). In northern Idaho, 

the resulting decay usually is 

restricted to the first log (Canfield 

1969). P. weirii is most damaging in 

the interior, attacking living trees 

only to a limited extent on the coast 

(Buckland 1946). 

Pestalotia funerea Desm. is associated with redcedar dieback in Washington (Crops Research Division, 

Agricultural Research Service 1960). 

27 
The shoestring root and butt rot, Armillaria mellea Vahl., attacks most 

conifer species in the Western 

United States (Scharpf 1978), but it 

is less damaging to western 

redcedar than to other species in 

the western white pine type (Hepting 

1971). Nevertheless, nearly half the 

redcedar trees released in an Idaho 

thinning study were infested with A. 

mellea (Intermountain Forest and 

Range Experiment Station 1962, 

Koenigs 1969). Canfield (1969) found 

A. mellea in 15 percent of the Idaho 

redcedars he sampled in old-growth 

stands but judged the resulting 

decay to be insignificant in merchantable wood. Some A. mellea occurs on western redcedars planted 

in New Zealand (New Zealand State 

Forest Service 1944). 

Phytophthora cryptogea Pethyb. & 

Laff. and P. citricola Sawada were 

isolated from roots of diseased 

western redcedars (Young and 

Strouts 1976). P. cinnamomi Rands 

also infects redcedar roots but does 

little damage (Evans 1978). Western 

redcedar seems to be resistant to P. 

cinnamomi (Robertson 1969) and P. 

lateralis Tuck. & J. A. Milb. (Milbrath 

and Young 1949). 

Redcedar seems to be resistant to 

the cypress canker caused by Monochaetia unicornis (Cke. & Ell.) Sacc. 

(Fuller and Newhook 1954) but susceptible to the crown gall caused by 

Agrobacterium tumefaciens (E. F. 

Smith & Town.) Conn. (Hepting 

1971). 

Trunk Rots 

Buckland’s (1946) investigations of 

decay in British Columbia western 

redcedar constitute the best general 

assessment of redcedar trunk rots. 

He ranked the major fungi in order 

of importance, with the most damaging listed first: 

Stem Diseases 

Western redcedar has no major 

stem diseases, but several minor 

fungi occur on weakened or dead 

redcedar stems: 

Aleurodiscus amorphus (pers. ex Fr.) 

Rab. (Hansbrough 1934, Hepting 

1971) 

Coastal British Columbia 

Poria asiatica (Pil.) Overh. 

Poria albipellucida Baxt. 

Fomes pini (Thore) Lloyd 

Merulius sp. 

Poria subacida 

Less common root- and butt-rot 

fungi hosted by western redcedar include: 

A. amylaceus Rog. & Jacks (Hepting 

1971) 

Corticum galactinum (Fr.) Burt 

(Hepting 1971) 

A. cerussatus (Bres.) Hoehn. & Litsch. 

(Hepting 1971) Interior British Columbia 

Fomes annosus (Fr.) Cke. (Crops 

Research Division, Agricu I t ural 

Research Service 1960, Hepting 

1971, Scharpf 1978) 

A. lividocoeruleus (Karst.) Lemke 

(Hepting 1971) 

Poria asia tica 

Phellinus weirii 

Fomes pini 

Polyporus balsameus Pk. 

Merulius sp. 

Poria subacida 

A. tsugae Yas. (Hepting 1971) 

Odontia bicolor (Alb. & Schw.) Bres. 

(Hepting 1971) 

A. weirii Burt (Hepting 1971) 

Chloroscypha seaveri (Hepting 1971) Other fungi that attack the heartwood of living redcedar stems less 

extensively were also identified by 

Buckland: 

Polyporus schweinitzii Fr. (Buckland 

1946, Gecow 1952, Crops 

Research Division, Agricultural 

Research Service 1960, Shaw and 

Harris 1960, Hepting 1971, 

Scharpf 1978) 

Coryneum cardinale Wagen. (Grass0 

1952, Sutton and Gibson 1972, 

Strouts 1973) 

Coniophora cerebella (Pers.) Pers. 

Fomes nigrolimitatus (Rom.) 

F. pinicola (Swartz ex Fr.) Cke. 

Omphalia campanella (Batsch. ex 

Egeland 

Fr.) Quhl. 

Cucurbidothis conjuncta Petr. (Hepting 1971) 

P. tomentosus Fr. (Hepting 1971) 

Diaporthe lokoyae Funk (Funk 1973) 

Poria subacida (Pk.) Sacc. (Buckland 

1946, Shaw and Harris 1960, Hepting 1971) 

Hendersonia thyoides Cke. & Ell. 

(Hepting 1971) 

P. vaillantii (DC. ex Fr.) Cke. (Crops 

Division, Agricu I t u ral Research 

Service 1960, Hepting 1971). 

Pestalotia funerea Desm. (Hepting 

1971) 

Valsa abietis Fr. (Hepting 1971) 

Poria subacida seems to be most 

i m port an t. V. kunzei Fr. (Hepting 1971) 

V. weiriana Petr. (Hepting 1971) 

28 
He found the major fungi decaying 

redcedar sapwood and slash to be 

Polyporus cuneafus (Murr.) Zell. and 

H ym e,noc ha e f e fa ba cina ([Sow .] 

Fr.) Lev. 

Kimmey (1956) found that Poria 

albipellucida accounted for about 45 

percent of the western redcedar 

trunk rot in southeastern Alaska. 

Phellinus weirii accounted for about 

41 percent, and Poria ferrugineofusca Karst. was responsible for 3 

percent. Kimmey found no sporophores on living redcedar trees in 

Alaska, so he used sucker limbs, 

trunk scars, dead sections, and rotten burls as decay indicators. 

Similar indicators were used by Canfield (1969), but Canfield found some 

fungal sporophores in northern 

Idaho. Phellinus weirii and Polyporus sericeomollis Rom. were the 

most common redcedar decay fungi 

identified by Canfield. He encountered slightly more decay where the 

fern Gymnocarpium dryopferis was 

present than where it was absent. 

lsenberg (1 951) rated Phellinus weirii 

as the most serious western redcedar decay, with Polyporus anceps 

Pk. and Fomes pini important on old 

trees. P. sulphureus Bull. ex Fr. 

damages redcedar trees in Washington (Shaw and Harris 1960), and 

Echinodonfium fincforium (E. & E.) 

E. & E. is occasionally found on 

western redcedars in British Columbia (Et heridge 1972). Young redcedar 

trees seem quite resistant to Fomes 

annosus (Fr.) Cke. in England and 

Poland (see Kosturkiewicz and Meixner 1956, Greig 1974, Forestry Commission, London 1978). 

Nelson (1976) found western redcedar heartwood resistant to colonization by Phellinus weirii. Similar 

work with Lenzifes frabea Pers. ex 

Fr. (Morton and French 1966) and 

decay tests with L. frabea, Fomes 

subroseus (Weir) Overh., Lenfinus 

lepideus Fr., Merulius lacrymans 

(Wulf.) Fr., and Coniophora pufeana 

(Schum. ex Fr.) Karst. (Scheffer 1957, 

Jacquiot and Lapetite 1960, Lutomski and Raczkowski 1963) have 

shown most redcedar heartwood to 

be resistant to most decay fungi. 

Resistance to Poria incrassafa (B. & 

C.) Burt and P. monficola Murr. is 

variable, however (Scheffer 1957), 

and dark-colored inner heartwood is 

less resistant to decay than lightcolored outer heartwood (see 

Findlay and Pettifor 1941, van der 

Kamp 1975). 

Dead western redcedar trunks were 

slowly decayed by Polyporus 

cuneafus (Murr.) Zell. (14.4 percent 

of the decay), P. versicolor L. ex Fr. 

(2.8 percent), and Fomes applanafus 

(Pers. ex S. F. Gray) Gill (0.7 percent) 

after being windthrown on the Olympic Peninsula (see Boyce 1929, 

Buchanan 1940). The decay probably 

occurred in sapwood. Eslyn and 

Highley (1976) found western redcedar sapwood resistant to soft-rot 

attack, moderately resistant to 

white-rot attack, and susceptible to 

brown-rot attack. 

Product Decay 

Several fungi were associated with 

brown sap rot of western redcedar 

poles in northern Idaho (Southham 

and Ehrlich 1950): 

Polyporus guffulafus Peck 

Coniophora pufeana 

C. arida (Fr.) Karst. 

C. olivacea (Fr.) Karst. 

C. olivascens (B. & C.) Massee 

Paxillus panuoides Fr. 

Poria vaillanfii (DC. ex Fr.) Cke. 

Merulius pinasfri (Fr.) Burt. 

Polyporus gutfulafus was most important in Idaho. Elsewhere, Lenzifes frabea Pers. ex Fr. is important 

(Eslyn 1970). Tests of decay resistance showed the lower and middle 

thirds of redcedar poles to be more 

resistant than the upper third 

(Englerth and Scheffer 1954). 

Extractives and Decay 

Heartwood color is associated with 

extractive content and decay resistance. Dark-colored heartwood near 

the center of a redcedar tree is low 

in both thujapliciris and resistance; 

light-colored heartwood near the 

periphery is high in both (van der 

Kamp 1975). The thujaplicins are 

highly toxic to a great variety of 

wood-destroying fungi (Erdtman and 

Gripenberg 1948b, Roff and Atkinson 

1954, Roff and Whittaker 1959, Rudman 1962, Freydl 1963). Indeed, thujaplicins are about as active as 

pent ac h lo ro p he n o I (Re n ne rf e I t 1 948) 

- concentrations of 0.001-0.002 percent inhibit fungus growth (Rennerfelt and Nacht 1955). They apparently inhi bit oxidative 

phosphorylation in the affected 

fungi (Lyr 1961). Many fungi may 

have the ability to chemically 

change nearby t h u j ap I ic i n ext ractives to nontoxic material, however, 

thus becoming able to overcome increasingly high concentrations of 

the toxic heartwood extracts 

(Southam and Ehrlich 1943). This 

may explain the great amount of 

heart rot in mature western redcedar 

- heart rot that progresses outward 

from the center of the tree and is 

associated with reduced thujaplicin 

concentrations in the older, central 

heartwood. 

29 
Birds and Mammals Horticulture 

Western redcedar seeds may be 

sown safely (McKeever 1942), for 

ground-feeding birds and small 

mammals prefer Douglas-fir and 

western hemlock to redcedar seeds 

in western Oregon (see Gashwiler 

1967). Pregermination rodent 

damage is minor (Helmers 1946, 

Boyd 1959). Redcedar mortality is 

high between the beginning and end 

of germination, however (Gashwiler 

1970), so birds and small mammals 

may be important during the germination period. 

Redcedar seedlings and saplings 

are browsed by deer and elk. They 

constitute one of the most important conifer foods of black-tailed 

deer in the coastal forest region of 

southern Vancouver Island (Cowan 

1945). Redcedar was more severely 

browsed than Douglas-fir, western 

hemlock, or Pacific silver fir on the 

Olympic Peninsula (Gockerell 1966). 

All small western redcedars in the 

lower cedar groves of the SelwayBitterroot wilderness in Idaho may 

have been destroyed by wintering 

deer and elk (Habeck 1978). 

Redcedar is a major winter food for 

big game in the northern Rocky 

Mountains. Deer browse redcedars 

all year long in British Columbia, 

and elk feed on them during the fall, 

winter, and spring (see Packee 

1975). Introduced Sitka blacktail 

deer have greatly reduced redcedar 

regeneration in large portions of the 

Queen Charlotte Islands. 

Black bears remove redcedar bark 

and feed on the exposed sapwood in 

western Washington (Radwan 1969). 

Opossums limit western redcedar 

growth in Westland, New Zealand 

(Weston 1971). 

Domestic animals also damage 

young western redcedars. Cattle 

browsed redcedar in preference to 

Douglas-fir in northwestern Oregon 

(see Howell 1948), and sheep 

damaged redcedar reproduct ion 

more than that of other trees in 

northern Idaho (Tisdale 1961). 

Redcedar seed orchards have been 

established in Denmark (SqJegaard 

1956b), where resistance to the leaf 

blight caused by Didyrnascella thujina has been shown to be homozygously recessive (SqJegaard 1956a, 

1966, 1969). SqJegaard’s invest igations indicate that frost resistance 

in western redcedar is inherited in 

the same way as leaf-blight resistance. Both seem to vary with stage 

of physiological development, but 

the redcedar clones most damaged 

by leaf blight are also most damaged by frost (see Larsen 1953). 

Tests of several seed sources in 

North America showed wide variations in frost hardiness. Trees grown 

from inland sources were hardier 

than those from coastal areas (Boyd 

1959, Sakai 1972, Sakai and Weiser 

1973). No significant difference in 

leaf-oil terpene composition was 

found between inland and coastal 

populations by Von Rudloff and 

Lapp (1979), however, who observed 

that western redcedar has one of 

the lowest degrees of variability 

found thus far in northern North 

American conifer species. Copes 

(1981) detected no isoenzyme variation 

among widely separated western redcedar populations in Oregon and Washington, suggesting that management of 

redcedar by cultural procedures may 

yield greater returns than genetic 

improvement programs. Nevertheless, 

plantation trials indicate that Alaska 

redcedar provenances are inferior to 

those from Oregon and Idaho when 

grown in Poland (Ilmurzyhski et al. 

1 968). 

Western redcedar is well suited for 

the use of haploidy in tree breeding 

(Winton and Stettler 1974). Von 

Pohlheim (1970, 1971, 1972, 1977a, 

1977b) studied somatic mutations 

and chimeras in haploid and triploid 

cultivars. 

Western redcedar is often cultivated 

as an ornamental tree in Europe 

(Sargent 1933). It is an excellent 

hedge shrub, standing trimming well 

and rarely spreading too far (Edlin 

1968). Redcedar hedges planted 

along roadsides in Switzerland 

deflected and partially filtered 

traffic-polluted air, reducing lead’ 

contamination at offroad locations 

(Keller 1974). 

At least three horticultural varieties 

of western redcedar are grown in 

North America (Rehder 1940). Thuja 

plicata var. atrovirens Sudw. has 

dark green leaves. The fastigiata 

Schneid. variety has columnar form, 

and variety pendula Schneid. has 

slender, pendulous branches. In addition, a haploid variety - gracilis 

Beissn. - has been studied in Germany. Von Pohlheim (1972) found 

this haploid variety less tolerant of 

irradiation and more subject to 

irradiation-induced mutation than 

the normal diploid. He selected a 

mutant form with pendent, filiform 

branches (von Pohlheim 1977a) and 

studied diploidization in the 

periclinal chimeric shoot apices of 

variety gracilis (von Pohlheim 1971, 

1977b). Simak et al. (1974) examined 

male strobilus development and 

microsporogenesis in this haploid 

variety. Thuja plicata excelsa Timm. 

is a triploid cultivar with thicker and 

darker leaves than T. plicata (von 

Pohlheim 1970). 

30 
Physiology and Ecology 

Meteorological Influences 

Temperature. - Western redcedar 

occupies a moderate position on the 

temperature gradient described by 

Zobel et al. (1976) for the central 

western Cascades of Oregon. It has 

as few as 75 frost-free days in some 

portions of interior British Columbia, 

at least 120 to 150 frost-free days 

along the coast (see Krajina 1969), 

where the average frost-free period 

is commonly over 200 days (Packee 

1976). Absolute minimum temperatures experienced by redcedar in 

British Columbia are - 10” to 

- 30°C (14” to - 22°F) in coastal 

populations, - 14” to - 47°C (7” to 

- 53°F) in the interior (Krajina 1969). 

Western redcedar is not very frost 

resistant, however; early and late 

frosts cause damage. Bottomland 

frost pockets in northern Idaho.are 

commonly occupied by subalpine fir 

rather than western redcedar 

(Daubenmire and Daubenmire 1968). 

An April frost of - 9°C (16°F) that 

followed a mild winter destroyed 

almost all the young western redcedars in a Scottish plantation in 

1945 (Hunter Blair 1946). An earlier 

April frost in England was less 

damaging to western redcedar than 

to Douglas-fir or Sitka spruce, however, and Day (1928) concluded that 

redcedar was more frost resistant 

than the other two species. Aldhous 

and Low (1974) observed that 

redcedar was also more resistant 

than grand fir or western hemlock to 

late spring frosts in Britain. 

Autumn frost damage seems to vary 

with location and preceding 

weather. An unusual September 

frost in Ireland damaged Douglas-fir, 

Sitka spruce, and Scotch pine more 

than western redcedar in 1972 

(Mooney 1973). In contrast, a November frost in Washington was more 

injurious to redcedar than to 

Douglas-f ir (Duff ield 1956, Daubenmire 1957) or Sitka spruce (Duffield 

1956). Sitka spruce seems more 

resistant than redcedar to winter 

cold (see Phillips 1965). Nevertheless, western redcedars withstand 

cold winters very well in Europe (see 

Gecow 1952, Degen 1965, Hesmer 

and Gunther 1968). When bright sunny days follow a period of belowfreezing temperatures, young 

redcedar branches and leaders often 

die in their native habitats (Miller 

1978). Dormant twigs from the interior were much hardier than those 

from the coast when subjected to 

subfreezing temperatures in a laboratory (Sakai and Weiser 1973). 

Western redcedar is susceptible to 

heat girdling (Haig 1936). It appears 

to be less tolerant of high soilsurface temperatures than Engelmann spruce, grand fir, or Douglasfir (Larsen 1940). The exposed surfaces of upper foliage in young 

redcedar seedlings often “sunburn” 

severely, but lower, unexposed surfaces remain green (personal communication, Edmond C. Packee, 

MacM i I Ian Bloedel Limited, 

N ana i mo, Brit i s h Co I u m b i a). 

Moisture. - Water content in 2-yearold western redcedar seedlings was 

higher than in Douglas-fir or western 

hemlock seedlings when all three 

species were grown in a greenhouse 

by Jablanczy (1964), but western 

redcedar leaves lose water rapidly 

when severed from the parent tree 

(Parker 1951). The leaves are not protected from excessive transpiration 

by cutin and wax, and they showed 

no drought resistance in the 

physiological and anatomical investigations conducted by Oppenheimer (1967). 

Redcedar is abundant in many 

forested swamps. It is sometimes 

found on sites that are too dry for 

western hemlock, however - in 

Montana (Habeck 1968, Pfister et al. 

1977), Washington and Oregon 

(Franklin and Dyrness 1973), British 

Columbia (Packee 1976), and Idaho 

(Daubenmire and Daubenmire 1968). 

Daubenmire (1966) placed western 

redcedar between western hemlock 

(cooler and wetter) and western 

white pine (warmer and drier) in the 

species series that he constructed 

along environmental gradients in 

eastern Washington and northern 

Idaho. Redcedar dominates wet 

ravines and poorly drained depressions in both Glacier National Park, 

Montana, and the Selway Bitterroot 

Wilderness, Idaho (Habeck 1968, 

1978), but it is almost absent where 

frequent flooding occurs in Glacier 

Park (Kessell 1979). Adequate soil 

moisture during the growing season 

seems to be essential for redcedar 

growth in Italy (Sanesi and Sulli 

1973). 

The generally observed superiority 

of western redcedar over western 

hemlock on dry sites seems to be 

the result of better redcedar root 

penetration (Haig 1936). Root 

penetration probably is not responsible for western redcedar superiority 

on wet sites, where it often is the 

dominant tree (fig. 3). Native 

redcedars are able to tolerate stagnant water tables in winter that 

average less than 15 cm (6 in) below 

the soil surface on the Olympic 

Peninsula (Minore and Smith 1971). 

Day (1957) found redcedars to be the 

characteristic dominants on waterretentive or wet soils in the Queen 

Charlotte Islands. Western redcedar 

seedlings tolerated year-round water 

table depths of only 7.5 cm (2.9 in) 

and 8 weeks of summer flooding in 

controlled experiments (Minore 1968, 

1970). 

31 
Figure 3.

-Western redcedars growing on a 

wet site in the Washington Cascades. 

Photoperiod. - Vaartaja (1957a) 

observed no significant response 

when he exposed l-month-old seedlings to a single 10-hour dark period 

and to two 5-hour dark periods in 

each 24

-hour day. Growth of the 

redcedars measured by Malcolm and 

Caldwell (1971), though erratic, indicated a critical day length of 

about 15 hours for the faster rates 

of growth. Western redcedar 

responds rapidly to increases in 

photoperiod, breaking dormancy 

faster than western hemlock or 

Doug I as-f i r (J ab I an czy 1 964). 

Wind. - Western redcedar is windfirm on dry sites, where Gratkowski 

(1956) rated it more windfirm than 

Douglas-fir, western hemlock, or 

Pacific silver fir. Boyce (1929) also 

classed redcedar with Douglas-fir as 

resistant to windfall. Western 

redcedar is fairly resistant to storm 

damage in Germany (Volk 1968) and 

stands up well to wind in Britain 

(Streets 1962). It is not windfirm on 

the wet sites characterized by 

Adiantum, Lysichitum, and Athyrium 

in British Columbia (Packee 1976). 

Air pollution. - Western redcedar is 

sensitive to atmospheric pollution in 

Britain (Streets 1962). In Germany’s 

industrialized Ruhr area, however, it 

seems more tolerant of industrial 

fumes than Douglas-fir or western 

hemlock (Glocker and Krussman 

1957). German tests showed little 

damage to western redcedar leaves 

after 57 hours exposure to 2.0 parts 

per million (plm) sulfur dioxide 

(Enderlein and Vogl 1966). Longer 

exposures may be more damaging; 

only grand fir and subalpine fir were 

more susceptible than redcedar 

when 12 conifers were tested for 

damage from sulfur dioxide smelter 

fumes in British Columbia (Scheffer 

and Hedgcock 1955). 

Western redcedar is less tolerant of 

ocean spray than Sitka spruce along 

the west coast of Vancouver Island, 

British Columbia (Cordes 1973). 

Redcedar also is intolerant of saltladen winds in Southland, New 

Zealand. In Westland, which has 

more rainfall, the salt damage is 

less serious (Weston 1971). 

32 
Clay dust from a brick works in 

British Columbia produced a columnar form in nearby western redcedars that led Glendenning (1948) 

to describe a new horticultural variety. When this columnar variety was 

grown in the absence of clay dust, 

however, it reverted to normal 

redcedar form (Rhodes 1955). 

The aromatic compounds produced 

by western redcedar can influence 

other plants. The germination of 

oats, wheat, and corn was retarded 

or inhibited by air that had been in 

contact with redcedar wood (Weintraub and Price 1948). 

Fire 

Western redcedar is very susceptible 

to fire injury (Lutz 1972). The shallow 

roots under a duff layer are often 

scorched when that duff layer burns 

(Flint 1925), and even surface fires 

may kill coastal western redcedar 

(McMinn 1960). Most low-site areas 

have fire-killed redcedar trees in 

southeastern Alaska, where western 

redcedar is very flammable (Gregory 

1957). Relative fire resistance of 

species does not appear to be the 

same in coastal and inland forests, 

however (Minore 1979). In the Rocky 

Mountains, redcedar is more resistant to fire than Engelmann spruce 

and western hemlock, less resistant 

than Douglas-fir and ponderosa pine 

(Haig et al. 1941). Old redcedar trees 

commonly are fire scarred in northern Idaho (Daubenmire and Daubenmire 1968). 

Fire-killed western redcedar timber 

shows little deterioration after 5 

years (Wallis et al. 1974). Even the 

bark usually remains intact on dead 

trees for 5 years (Embrey 1963). Fire 

killing produces no immediate 

reduction in strength of western redcedar poles (Research News, Ottawa 

1962~)~ and some large redcedar 

trees remain salvageable for almost 

100 years after being killed by fire 

(see Smith et al. 196lb). 

Physical properties. - Western 

redcedar seems able to tolerate a 

wide range of physical properties in 

soil in most localities. It is found on 

all landforms, soil textures, and 

parent materials on Vancouver 

Island (Packee 1976). Coarse sandy 

soils are not well suited to 

establishment and growth of redcedar in northern Idaho and northeastern Washington, however - 

they are too droughty and unstable 

(Helmers 1946). In contrast, rocky 

slopes with limited soil development 

support western redcedar in southeastern Alaska (Gregory 1957). The 

wet soils developed from muskegs 

also are dominated by western 

redcedar south of Petersburg, 

Alaska (Stephens et al. 1970). It 

grows over loams, clays, sands, and 

chalk downland in England (Hubbard 

1950, Streets 1962, Edlin 1968). 

Redcedar also grows on MolinaJuncus peat there (Zehetmayr 1954). 

Forristall and Gessel (1955) concluded that western redcedar roots 

could grow in higher bulk densities 

of soil than could roots of red alder, 

Douglas-fir, or western hemlock. Unfortunately, they compared species 

growing separately on soils of differing textures. Minore et al. (1969) 

used a soil of uniform texture in the 

greenhouse and found that western 

redcedar roots could not penetrate 

the compacted soil columns penetrated by Douglas-fir, red alder, 

lodgepole pine, and Pacific silver fir. 

Forest floors under western redcedar and Sitka spruce tend to be 

thicker and have higher waterholding capacities than those under 

Douglas-fir and western hemlock in 

western Washington (Flannery 1940). 

Chemlcal properties. - Total 

amounts of essential plant nutrients 

stored in the forest floor were 

greater under western redcedar and 

Sitka spruce than they were under 

Douglas-fir and western hemlock in 

the stands sampled by Flannery 

(1940) in western Vl’ashington. The 

data of Tarrant et dl. (1951) and 

Daubenmire (1953) indicate that 

western redcedar litter is low in 

nitrogen and phosphorus, so Flannery’s figures may have resulted 

from greater thickness rather than 

higher concentrations. Alban (1969) 

measured more exchangeable calcium, higher cation-exchange 

capacity, and higher base saturation 

in soils under redcedar than under 

western hemlock, however, and he 

found soil pH to be higher under the 

redcedar. Ovington and Madgwick 

(1957) found pH higher in soil under 

redcedar than under European 

beech, European larch, Sitka spruce, 

oaks, Norway spruce, Scotch pine, 

Japanese larch, Austrian pine, birch, 

grand fir, noble fir, Douglas-fir, 

lodgepole pine, western hemlock, 

and tamarack. Western redcedar 

seems to benefit the soil. It is one 

of the few species that can be 

grown on chalk downland in 

southern England (Aldhous and Low 

1974). 

Krajina (1969) observed that redcedar growth seems to be benefited 

by nitrification, and he associated 

the presence of Sambucus racemosa L., Tiarella trifoliata L., Tellima 

grandiflorum (Pursh) Dougl., Tolmiea 

menziesii (Pursh) T. & G., and Urtica 

dioica L. with favorable soil conditions. 

33 
Nutrients and Nutrition 

The nutrient contents of western 

redcedar foliage vary with season 

and site. Nevertheless, relatively 

high concentrations of calcium and 

low concentrations of nitrogen are 

nearly always present (see Gessel et 

al. 1951, Tarrant et al. 1951, Daubenmire 1953, Ovington 1956, Beaton et 

al. 1965, Webber 1973). Phosphorus 

concentrations are usually low, but 

Smith et al. (1968) found them to be 

higher in western redcedar than in 

Douglas-fir or western hemlock. 

Less sulfur was found in redcedar 

foliage than in the foliage of other 

British Columbia conifers sampled 

by Beaton et al. (1965). 

Fo I i age- n ut r i en t concen t rat ions 

should be used with caution when 

comparing species, for relative 

nutrient concentrations do not 

always reflect relative nutrient requirements. Optimum nutrition of 

western redcedar may require very 

high nutrient levels (Krajina 1969). 

Redcedar seedlings apparently require more nitrogen than seedlings 

of Sitka spruce, western hemlock, or 

Douglas-fir for best growth (Krajina 

1959), but redcedar can survive on 

poor sites (Gregory 1957). Redcedar 

may respond to nitrogen additions 

by increasing root growth in comparison with shoot growth (Smith et 

al. 1968). Although nitrate nitrogen 

seems to be used more efficiently 

than ammonium nitrogen in sand 

and solution cultures (see Krajina 

1971, Krajina et ai. 1973), additional 

work is needed to relate soil nitrate 

and ammonium to redcedar growth 

in nature. Nitrogen deficiencies 

result in yellowish foliage, reddish 

seedling stems, and foliage nitrogen 

concentrations less than 1.5 percent 

(Walker et al. 1955). 

Phosphorus deficiencies result in 

reddish or purplish stems and older 

foliage (Walker et al. 1955). Although 

phosphorus and nitrogen deficiencies were blamed for plantation 

check in the upland heaths of Britain (Forestry Abstracts 1964), and 

phosphorus additions benefited root 

growth of western redcedar on sodpeat bog in Ireland (Carey and Barry 

1975), redcedar is more tolerant of 

low phosphorus levels than Douglasfir and Sitka spruce (Krajina 1969). 

Potassium deficiencies do not seem 

as critical as deficiencies of 

nitrogen or phosphorus for western 

redcedar growth (see Walker et al. 

1955). Walker et al. measured little 

decrease in seedling growth under 

pot assi u m-def icien t conditions but 

noted limber stems and drooping 

foliage on the affected seedlings. 

Seedlings affected by calcium deficiencies show browning and dying 

at the tips of leader and branch 

shoots (Walker et al. 1955). Western 

redcedar may be less tolerant than 

western hemlock, Sitka spruce, or 

Douglas-fir to low levels of calcium, 

magnesium, or both (Krajina 1959, 

1969). 

Only low levels of sulfur seem to be 

required by western redcedar. Indeed, sulfur fertilization often 

caused reduced height growth of the 

western redcedars treated by Smith 

et al. (1968). This response may have 

been the result of pH changes induced by the fertilization, however, 

for western redcedar is reputed to 

grow best on neutral to slightly acid 

sites (University of British Columbia 

Forest Club 1959). Where sulfur deficiencies do occur, young redcedar 

foliage becomes yellowish and older 

foliage is paler than normal (Walker 

et al. 1955). 

Western redcedar seedlings survive 

in the absence of boron, but they 

develop a variety of deficiency 

symptoms: Stem elongation is much 

restricted, and needles are closely 

bunched (Walker et ai. 1955); 

branches become straplike or club 

shaped (Blaser et al. 1967); and 

stems are weak. 

Comparisons of western redcedar 

f o I i ag e- n u t r i e n t concentrations, 

growth responses, and site conditions are sometimes confusing. 

Much of this confusion may result 

from a failure to distinguish between responses to low nutrient 

levels and responses to optimal 

nutrient levels. Western redcedar 

seems able to survive and grow in 

low-nutrient conditions, and it probably occurs in such conditions over 

much of its natural range. When 

supplied with abundant nutrients 

and moisture, however, redcedar 

may respond more vigorously than 

other conifer species. For example, 

western redcedar seedlings outgrew 

seedlings of Douglas-fir, grand fir, 

Sitka spruce, western hemlock, and 

ponderosa pine when all were grown 

for 2 years in raised, well-watered 

soil beds fertilized with nitrogen, 

phosphorus, and p0tassium.g 

Asexual Reproduction 

Three types of asexual reproduction 

of western redcedar occur in nature: 

layering (Schmidt 1955; Habeck 

1968, 1978), rooting of fallen 

branches, and branch development 

on fallen trees. The resulting “veglings” were more abundant than 

seedlings in mature stands sampled 

by Parker (1979) in northern Idaho. 

Much of the redcedar regeneration 

observed by Dyrness et al. (1974) in 

the western Cascades of Oregon 

consisted of individuals developed 

from branches of saplings that were 

knocked down and have since 

rooted. 

Taper, “Growth of forest tree seedlings 

in sewage sludge amended media,” by 

R.J. Zasoski and C.S. Bledsoe. 1980. 

Presented at the 53d annual meeting, 

Northwest Scientific Association, in 

Moscow, Idaho. Abstract on file, 

Forestry Sciences Laboratory, Corval I is, 

Oregon. 

i 

34 
Redcedar clones are easily propagated by rooting stem cuttings 

(Larsen 1953). Untreated cuttings 

. will root, and SQegaard (1956a) 

achieved 50 to 80 percent success 

by using new shoots cut in July and 

August. Nevertheless, treatment 

with growth-regulating substances 

improves results. Verleyen (1948) 

found a-napthalene acetic acid more 

effective than /I-indole-acetic acid in 

early rooting trials. Indole-butyric 

acid (I.B.A.) improves rooting speed, 

the number of cuttings rooted, and 

the total length of roots per cutting 

(Matthews 1951). The best I.B.A. concentrations are 3,000 plm for a 

1-minute dip and 200 to 400 plm for 

a 4-hour soak (Kalmhr 1973). When a 

talc carrier is used, 6.25 plm is effective (Matthews 1951). 

Coleman and Thorpe (1977) successfully grew western redcedar 

plantlets from both juvenile and 

mature tissues by applying distinct 

sequential treatments for the following developmental stages: meristemoid induction and adventitious bud 

determination; bud growth; and 

rooting of the resulting advent it ious 

shoots and reestablishment in soil. 

Compositions of the nutrient media 

used in stem tissue cultures are 

listed by Harvey and Grasham (1969) 

and Coleman and Thorpe (1977). 

Sexual Reproduction 

Sexual reproduction probably is 

more important than asexual 

reproduction in open clearcut units 

and other disturbed areas (see 

Parker 1979). When grown in the 

open, western redcedar trees begin 

to produce strobili at 10 years of 

age and usually continue every other 

year thereafter (Sqegaard 1956a), but 

large seed drops occur only every 3 

to 4 years (Schopmeyer 1974). 

Strobilus formation is induced by 

branch-girdling in western redcedar 

(Forestry Commission, London 1970; 

Longman 1976). Treatment with gibberellins also induces stiobilus formation (Coutts and Bowen 1973, 

Longman 1976). Indeed, staminate 

strobili can be induced in 7- to 

9-month-old redcedar seedlings by 

applying foliar sprays of gibberellin 

A, under long-day conditions (Pharis 

and Morf 1967). Long days were 

used by Coleman and Thorpe (1978) 

to induce staminate strobilus formation in western redcedar shoot tips 

cultured on nutrient media in the 

presence of high gibberellin concentrations. Simak et al. (1974) also 

used long days and gibberellin to induce staminate strobili in redcedar 

cuttings. A short photoperiod, cold 

treatment, or both must be applied if 

strobili are to develop further, however (Pharis et al. 1969, Pharis and 

Morf 1972). Pharis and his coworkers combined the gibberellin treatment with a sequence of long day, 

short day, long day to produce both 

staminate 'and ovulate strobili on 

young redcedar seedlings. They 

found that cold temperatures during 

the short-day treatment increased 

the number of developing strobili 

and that cold alone was effective, 

regardless of photoperiod. 

Under natural conditions on Vancouver Island, staminate strobili are 

initiated during the long days of 

early June, and ovulate strobili are 

initiated during the long days of 

early July (Owens and Pharis 1971). 

Meiosis begins in the fall, but it is 

arrested at the pachytene stage from 

November until late January (Owens 

and Molder 1971). Development resumes in February near Victoria, British 

Columbia, where pollination occurs in 

early March and fertilization is accomplished in late May (Owens and 

Molder 1980). Pollination is delayed 

until late May or early June in northern 

Idaho (Schopmeyer 1974). Peak pollen 

release occurs around noon, when relative humidities are low (Haard 1971). 

Self-pollination is common (Splegaard 

1956a). The pollination mechanism in 

western redcedar does not allow an 

accumulation of pollen, and redcedar 

ovules are not all receptive at the same 

time, so several sources of pollen shed 

over a prolonged period are advantageous (Owen and Molder 1980). 

Western redcedar cones mature 

about 5 months after pollination 

west of the Cascades, about 3 

months after pollination in northern 

Idaho (Schopmeyer 1974). Seedfall 

begins soon thereafter, continuing 

throughout the following winter in 

most locations (see Haig et al. 1941, 

Fowells 1965, Gashwiler 1969). 

Heavy seed crops are common (see 

Garman 1955, Schmidt 1955, 

Gashwiler 1969, Harris and Farr 

1974). 

Western redcedar seeds retain their 

initial viability for at least 3 years 

when stored at - 18°C (- 0.4"F) 

(Barton 1954, Holmes and Buszewicz 

1958). Some germinat ion occurred 

after 6 years when Allen (1957) 

stored redcedar seeds at 0 "C (32 OF), 

but - 18°C (- 0.4"F) seems to be a 

better storage temperature. Stratification may improve the germination 

of some dormant seed lots (Schopmeyer 1974). In others, it may lower 

the germination capacity (Jablanczy 

1964). Schopmeyer cites a 0.2-percent solution of potassium nitrate in 

the germination medium as an alternative to cold stratification. 

35 
Area and Event 

Coast: 

Beginning of shoot growth 

Major shoot growth 

End of shoot growth 

Beginning of radial growth 

End of radial growth 

Anthesis 

Beginning of seedfall 

Major seedfall 

End of seedfall 

I n t er i or: 

Beginning of shoot growth 

End of shoot growth 

Anthesis 

Beginning of seedfall 

Major seedfall 

A 

m 

- 

I 

Month 

J 

- AS0 D - 

I 

Figure 4.-Phenology of native redcedar, by 

area (from Haig et al. 1941, British Columbia Forest Service 1950, Garman 1955, 

Buckland 1956, Pacific Northwest Forest 

and Range Experiment Station 1957, Hedlin 

1964, Hetherington 1965, Williams 1968, 

Owens and Pharis 1971, Schopmeyer 1974, 

Schmidt and Lotan 1980). 

Phenology 

Phenological observations vary with 

year and locality. Therefore, the 

observations summarized in figure 4 

probably were influenced by the 

years and locations in which they 

were recorded. 

Phenological comparisons among 

species may be less influenced by 

seasonal and spatial variations. 

Western redcedar had the longest 

height-growth season of any conifer 

measured by Williams (1968) in the 

upper slope forests of Oregon. 

Walters and Soos (1963) found that 

leader growth commenced earlier 

and accelerated faster in redcedar 

than in Douglas-fir, western hemlock, or western white pine, but then 

continued at a lower rate - for a 

longer period - than in the other 

species. 

Radial growth phenology is not as 

easy to compare. It seems to vary 

among species from year to year 

(Reukema 1965). Redcedar radial 

growth periods are strongly influenced by altitude in the interior (see 

Dau benmire 1946). 

Regenerat ion 

Western redcedar regeneration probably is seldom limited by lack of 

seed. A fair seed crop on four trees 

produced over a million seeds in 

British Columbia (Garman 1951), and 

nine trees in a mature stand produced an average seedfall of over 2 

million seeds during 3 crop years 

(Garman 1955). The average annual 

crop in the coastal forests of British 

Columbia usually ranges from 

247,000 to 2,470,000 seeds per hectare (100,000 to 1,000,000 seeds/ 

acre) in stands with up to 25 percent 

redcedar (Schmidt 1955), but pure 

stands may yield over 148 million 

seeds per hectare (60 million 

seedslacre) (Sharpe 1974). In the 

interior, average seed crops range 

from 54,000 to 274,000 seeds per 

hectare per year (22,000 to 11 1,000 

seedslacre per year) (see Fowells 

1965, Clark 1970). 

36 
Western redcedar seeds tend to be 

sound as well as numerous. In a 

scrub stand in Alaska, 68 to 92 percent of the 38 million seeds per hectare (15 million seedslacre) produced 

in 1956 were sound (James 1959). 

Although he recorded great variations in size of redcedar seed crop, 

Gashwiler (1969) found a higher percentage of filled seeds for western 

redcedar than for Douglas-fir or 

western hemlock in west-central 

Oregon. Redcedar seeds fall faster 

and do not fly as far as the seeds of 

western hemlock, Sitka spruce, or 

Douglas-fir (see Siggins 1933). 

As western redcedar seeds are 

usually abundant and sound, an 

abundance of young redcedar trees 

would be expected on most redcedar sites. Surprisingly, they are 

not present in many environments. 

Immature stands are uncommon in 

coastal British Columbia (see 

Packee 1976). Seedlings are either 

rare (Neiland 1971) or they have difficulty surviving (Gregory 1957) in 

southeastern Alaska. They are also 

rare on both well-drained undisturbed sites and cutover areas on 

Graham Island, British Columbia 

(Day 1957). 

Moist redcedar sites on Graham 

Is land regenerate if u nd ist u r bed 

(Day 1957), and regeneration from 

seed is often successful on open 

areas disturbed by logging, windthrow, or fire in the coastal forests 

of British Columbia (Schmidt 1955). 

Moist redcedar sites also regenerate 

in Montana’s Glacier National Park, 

but the regeneration is vegetative 

(Habeck 1968). Western redcedar is 

not reproducing at all in low 

elevation redcedar communities 

within the Selway-Bitterroot 

wilderness of Idaho (Habeck 1978). 

Habeck attributed this to high 

populations of wildlife and a 

deterioration of the moist Pacific 

maritime influence in Idaho. Farther 

north, in the interior wet belt of 

British Columbia, 150,000 redcedar 

seeds were required to produce 

1,000 2- to 5-year-old seedlings in a 

121 5hectare (300-acre) clearcut 

unit, but natural regeneration was 

adequate on disturbed sites within 

100.6 m (330 ft) of a seed source 

(Clark 1970). 

The failure of redcedar regeneration 

on some sites and the high seedsto-established-seedl ing rat io on 

other sites are puzzling. Failures 

probably are not because of seed 

losses. Gashwiler (1967) found that 

a large proportion of his redcedar 

seeds survived until germination, 

which began later and finished 

sooner than the germination of 

western hemlock seeds (Soos and 

Walters 1963). Almost no germination occurs after the 1st year (Isaac 

1940), but enough redcedar seeds 

should germinate to insure success 

on most sites. Mortality is high during the germination period, however 

(see Gashwiler 1970), and seedbed 

quality may be critical. 

Germination was greater and more 

uniform under sand than under grit 

when redcedar seeds were covered 

in British experiments (Forestry 

Commission, London, 1978). Sand 

was a poorer seedbed than western 

white pine duff in Fisher’s (1935) 

greenhouse experiments. The artificial conditions inherent in many 

greenhouse experiments sometimes 

produce misleading results, how 

ever, and those results should be 

applied to field situations with geat 

care, if at all. In field experiments, 

Haig et al. (1941) found western 

redcedar germination to be 5 to 10 

times better on mineral soil than on 

duff. Mineral soil also is a better 

seedbed than moss in southeastern 

Alaska, but western redcedar seedlings seem to survive better than 

those of other species on the moss 

(Godman 1953). Average field survival of germinated western redcedar seeds was slightly higher on 

rotten Sitka spruce wood than on 

rotten Douglas-fir wood, rotten hemlock wood, or duff on light and 

moderately shaded seedbeds in 

coastal Oregon (Minore 1972). Heavily shaded seedbeds were associated with the best redcedar germination in coastal British Columbia 

(Garman 1955), where germination 

occurs throughout fall and winter 

when temperatures are favorable 

(personal communication, Edmond 

C. Packee, MacMillan Bloedel 

Limited, Nanaimo, British Columbia). 

Although Soos and Walters (1963) 

found that unburned mineral soil 

favors redcedar survival more than 

burned mineral soil, burning after 

logging may favor the natural 

regeneration of western redcedar 

(British Columbia Forest Service 

1948b). It probably creates more 

mineral soil surfaces in cutover 

areas. Growth of redcedar seedlings 

was better on burned and denuded 

surfaces than on organic material in 

nort hern Idaho (Larsen 1940). Seedling survival is usually best on 

mineral soil and poorest on rotten 

wood (Boyd 1959), but growth of the 

survivors may be best on wood; 80 

percent of the dominant redcedars 

examined by Nystrom (1980) grew on 

rotten logs, but only 36 percent of 

the suppressed trees were on rotten 

wood. 

Throughout the range of western 

red ced ar, disturbance of seed beds 

seems to be beneficial. Partial 

shade is also beneficial. Drought 

and high soil surface temperatures 

damage seedlings in full sunlight, 

and poor root penetration causes 

drought damage in full shade 

(Sharpe 1974). Fungi probably cause 

the greatest early mortality (Boyd 

1959). 

37 
Shade Tolerance 

Baker (1949) listed western redcedar 

as very tolerant. Although Schmidt 

(1955) observed that redcedar did 

not have all the characteristics 

usually associated with a shadetolerant tree, most authors seem to 

agree with Baker’s assessment. 

Redcedar is slightly less tolerant 

than western hemlock in southeastern Alaska and the south coast 

region of British Columbia (Packee 

1976). It is also less tolerant than 

Pacific silver fir in British Columbia 

(Krajina 1965, Packee 1976). Redcedar may be more shade tolerant 

than western hemlock in the interior 

(see Haig et al. 1941). The literature 

indicates that shade tolerance of 

western redcedar along the coast 

may be higher in warmer zones than 

it is in cool zones (Packee 1976). 

Succession 

Western redcedar is often present in 

all stages of forest succession, and 

Packee (1975) listed its successional 

positions as pioneer, seral, and 

climax. Multiple attributes seem to 

be responsible, for redcedar invades 

disturbed areas as widely distributed seeds but regenerates vegetatively in undisturbed areas, tolerating competition in both situations 

(Kessell 1979). Nevertheless, redcedar is usually considered a climax 

or near-climax species (see Munger 

1940, Guiguet 1953, Schmidt 1955, 

McLean and Holland 1958, Mueggler 

1965). Idaho western white pine 

stands are slowly replaced by a 

western hemlock-redcedar climax 

(Watt 1960). Daubenmire and 

Daubenmire (1968) listed redcedar 

as the major climax species in their 

Thuja plica talPa ch is tim a, Thuja 

plicatalOplopanax, and Thuja 

plicatalAthyrium habitat types in 

Idaho. It is a minor climax species 

in their Tsuga heterophyllal 

Pachistima type. Pfister et al. (1977) 

listed redcedar as a major climax 

species in Montana’s Thuja plicatal 

Clintonia uniflora habitat type, a 

minor climax species in the Tsuga 

heterophyllalClintonia uniflora type. 

Western hemlock may eventually 

replace western redcedar in some 

decadent stands of southeastern 

Alaska (see Gregory 1957). Redcedar 

will be part of the climax forest on 

wet sites in the Tsuga heterophylla 

zone of Oregon and Washington, but 

it probably does not have climax 

status on modal or dry sites 

(Franklin and Dyrness 1973). 

Moisture and soil conditions 

strongly influence the successional 

status of western redcedar. It is 

climax on wet sites in the Lake 

McDonald region of Glacier National 

Park (Habeck 1968) and on calciumrich seepage habitats in British Columbia (Krajina 1969). Redcedar 

probably is an edaphic climax 

species rather than a climatic 

climax tree. Longevity should not be 

ignored when considering successional status, however, and very old 

redcedar trees are often present in 

climatic climax situations. 

Growth 

Radial growth is similar in western 

redcedar and western hemlock 

(Walters and Soos 1962), but most of 

the pseudotransverse cell divisions 

in redcedar cambium occur near the 

end of the growing season (Bannan 

1951). Both species produce nonrigid leaders, but they differ in proportions of lateral and leader 

growth. Growth of lateral branches 

is less than half of leader growth in 

western hemlock and more than 80 

percent of leader growth in western 

redcedar (see Buckland 1956). 

Growth rates of lateral and terminal 

shoots were similar in the young 

western redcedars measured by 

Walters and Soos (1963). 

Growth is not always rapid. Suppressed redcedar trees that are 200 

years old but only 7.6-cm (3-in) d.b.h. 

and 7.6-m (25-ft) tall are not unusual 

(Schmidt 1955). Ability to survive 

such long periods of suppression 

may result from the ability of 

western redcedar to produce new 

root growth in full shade (see Haig 

1936). It may also be a result of frequent root grafting. Eis (1972) found 

that dominant trees usually supported growth of the root systems 

and lower boles of suppressed trees. 

However they survive, these suppressed trees often recover well 

when released. 

Forest inventory data show western 

redcedar trees in Oregon and Washington to be smaller in diameter and 

shorter than Douglas-firs and hemlocks of the same age on most sites 

(Bolsinger 1979). This is also true on 

well-drained soils in the south coast 

region of British Columbia. On moist 

sites, however, the coastal redcedar 

often is as large or larger than its 

associates (Packee 1976). Packee 

cites annual radial increments of 1 

or even 2 cm (0.4 to 0.8 in) on the 

best moist sites. 

Day (1957) found that vigor of 

western redcedar declined more 

slowly than that of Sitka spruce or 

western hemlock as site conditions 

became poorer on the Queen Charlotte Islands of British Columbia. 

This slower decline in relative vigor 

with decreasing site quality was not 

evident in the measurements of 

young tree growth recorded by 

Walters et al. (1961) on the lower 

mainland. Indeed, the opposite trend 

was apparent - young western redcedars grew faster than young western hemlocks and Douglas-firs on 

good sites, slower on poor sites. 

Ages of the trees being compared 

probably were responsible for these 

differences. Although western redcedar may not attain its most rapid 

growth rate until it is 10 to 30 years 

old (Jackson and Knapp 1914), it 

grows taller than western hemlock 

or Douglas-fir during the first 5 

years on good sites (see Smith and 

DeBell 1973). Smith and DeBell’s 

data show that Douglas-fir overtakes 

western redcedar by age 10, and 

western hemlock overtakes redcedar 

by age 15. 

30 
Growth of western redcedar tends to 

be faster than that of Alaska-cedar, 

but it may be extremely slow on 

poor sites in southeastern Alaska 

(Harris and Farr 1974). Height 

growth may reach a maximum at an 

early age in southeastern Alaska 

(Andersen 1955b). Nearby, along the 

north coast of British Columbia, approximately 10 years are required to 

produce a 1.2-m-tall (4-ft-tall) redcedar on average sites. Diameters of 

0.5 to 4.6 cm (0.2 to 1.8 in) are produced on better sites during the 

same 10-year period (see British Columbia Forest Service 1948b). Western redcedars in the United States 

may require 80 years to reach 

diameters of 25 to 46 cm (10 to 18 

in) (Lutz 1972). 

Redcedar growth rates seem to be 

impaired by a droughty soil-moisture 

regime or highly leached soils on 

Vancouver Island, British Columbia 

(McMinn 1960). Redcedar seems to 

grow slower than western hemlock 

but faster than Pacific silver fir.on 

coastal Douglas-fir sites (see 

Walters and Haddock 1966). 

Growth of redcedar is slow in the inland western white pine type, and 

redcedar often forms an understory 

after being outgrown by associated 

species (Haig et al. 1941). Even 

when released, it often cannot keep 

up with grand fir, western hemlock, 

and western white pine in northern 

Idaho (Deitschman and Pfister 1973). 

Slow growth during the first few 

years makes Rocky Mountain redcedar more susceptible to drought 

and insolation injury than its faster 

growing associates (Sc h o p meye r 

1940, McKeever 1942). Diameter 

growth of Rocky Mountain redcedar, 

however, is less affected by high 

elevation than the diameter growth 

of ponderosa pine or Douglas-fir 

(Dau benm i re 1955). 

Western redcedar growth varies 

greatly with site quality in Britain. 

Redcedar grew taller than Douglasfir or Sitka spruce in a 14-year-old 

British plantation, and a 20-year-old 

western redcedar plantation 

achieved a height of 16.8 m (55 ft) 

and a total volume of 2.1 m3/ha (30 

ft3/acre) (MacDonald 1957). These 

plantations probably were on exceptionally favorable sites, however, for 

Aldhous and Low (1974) found that 

the early growth of western redcedar 

was slower than that of Douglas-fir 

and Sitka spruce on most British 

sites. Growth tends to accelerate 

slightly after about 25 years (Evans 

1950). Redcedar eventually outproduces Sitka spruce on British 

lowland sites. It becomes increasingly more productive than Douglasfir as British site quality improves 

(see Aldhous and Low 1974). Indeed, 

Packee’s (1976) analyses of the 

paired-plot comparisons made by 

Aldhous and Low indicate that redcedar volume growth exceeds that 

of Douglas-fir on most British sites. 

Growth of redcedar also varies with 

site quality elsewhere in Europe. 

Dominant ,western redcedars in 

France have attained average 

heights of 19 m (62 ft) in 39 years 

(Andre and Lheureux 1974). Younger 

western redcedars in Germany grew 

to an average height of 7.6 m (25 ft), 

with at least one tree reaching a 

height of 10.8 m (35 ft) in 18 years 

(Zimmerle and Linck 1951). Danish 

redcedars have reached heights of 

20 to 25 m (66 to 82 ft) in 50 years 

(Madsen 1977). Growth in the 

Ukraine is slower, and the largest 

western redcedars there were only 

22 m (72 ft) tall at age 70 (Unasylva 

1950). 

Productivity 

Published production data for native 

western redcedar are rare, but three 

North American studies are available. In the first, Smith and DeBell 

(1973) assessed the productivity of 

short-rotation redcedar and found it 

poorer than that of Douglas-fir, 

western hemlock, or black cottonwood. In a second study, Nokoe 

(1978) developed a yield curve for 

medium-site western redcedar at 

Salmo, British Columbia: 

Age Net volume 

(mVhaY) 

40 70 

80 21 0 

115 350 

165 490 

270 595 

His mathematical models indicate 

that the maximum current annual increment occurs at 82 years and the 

maximum mean annual increment at 

130 years for a medium site. For a 

poor site, the ages are 133 and 210 

years, respectively. 

In the third study, Nystrom (1980) 

measured volumes of 379 to 824 

m3/ha (5,418 to 11, 782 ft3/acre) in 

4040 60-year-old, pure, secondgrowth stands of redcedar in 

western Washington. Of the 939 to 

3,657 redcedars per hectare (380 to 

1,480 per acre) in these young 

stands, 297 to 6421ha (120 to 

260/acre) were dominants with a 

mean annual height growth of 0.5 m 

(1.64 ft) per year. 

9To obtain ft3/acre, multiply m3/ha by 

14.291 4. 

39 
Table 6 - Growth and yield of western redcedar in Britain' 

Basal area of Average age 

Cumulative volume fully stocked of maximum 

Site and production in stands before mean annual 

height normal stands thinning increment 

Poor sites: 

Age 20 

Age 80 

Good sites: 

Age 20 

Age 80 

Stand height: 

10 meters 

12 meters 

20 meters 

30 meters 

Cubic meters Square meters 

per hectare2 per hectare3 Years 

72 

50 

953 

58 

232 

1838 

100 

600 

1400 

49 

55 

70 

lAdapted from Hamilton and Christie (1971). 

2Multiply by 14.2914 for cubic feet per acre. 

3Multiply by 4.3560 for square feet per acre. 

More information on productivity is 

available for western redcedar 

grown outside its natural range. A 

Montana provenance of redcedar 

planted in Austria in 1897 produced 

yields and stem forms comparable 

to those of Norway spruce grown in 

the same district (Rannert 1976). 

Redcedar equaled or exceeded the 

yield of Norway spruce in northwestern Germany, but it was inferior 

to Douglas-fir when both North 

American species were grown there 

(Hesmer and Gunther 1968). Western 

redcedar also produced less than 

Douglas-fir during a trial of species 

in East Germany. Nevertheless, its 

mean annual increment (12.5 m3/ha 

or 178.6 ftslacre) was not far below 

that of Douglas-fir (13.9 mVha or 

198.6 ft3/acre), and redcedar increment exceeded the mean annual increments of Norway spruce (10.8 

m3lha or 154.3 ftalacre), Japanese 

larch (10.2 m3/ha or 145.8 ftslacre), 

European beech (9.6 mVha or 137.2 

ft3/acre), and Scotch pine (8.8 mVha 

or 125.8 ftslacre) on a good site near 

Eberswalde (Lembcke 1970). 

The mean annual increment of a 

57-year-old western redcedar plantation in the Wirty State Forest of 

Poland was 13.0 mVha (185.8 

fWacre). When previous thinning 

was included, its total yield of 939.5 

m3/ha (13,426.7 ft3/acre) was nearly 

twice that for pine of the same age 

and site quality (see Gecow 1952). 

Although redcedar also matched or 

exceeded the production of native 

European species in Poland's 

Krynica Forests, both grand fir and 

Douglas-fir produced more than 

western redcedar there (Jaworski 

and Majerczyk 1975). 

Western redcedar productivity in 

France apparently varies greatly 

with stand age, stand density, and 

the environment in which it is 

grown. Turpin and Pard6 (1959) 

found that a young redcedar stand 

produced 13 m3lha per year (186 

ft3Iacre per year) on the Barres 

Estate - more than Douglas-fir 

(12.3 m3/ha per year or 176 ft3/acre 

per year) and second only to 

western hemlock (14.8 mVha per 

year or 212 ftVacre per year). In contrast, Guinier (1951) observed that an 

85-year-old Douglas-fir stand on the 

Harcourt Estate would produce 

about twice as much (800 m3/ha or 

11,433 ftslacre) as an 80-year-old 

western redcedar stand (400 m3lha 

or 5,716 ftslacre) if both had 250 

trees/ h a. 

40 
Mensuration 

Danish redcedar plantations also 

vary in productivity. Two plantations 

in eastern Denmark maintained 

periodic annual increments of 21 to 

35 mVha (300 to 500 fWacre) until 

age 46. One plantation then declined 

to a periodic annual increment of 16 

to 18 m3/ha (229 to 257 ftVacre), but 

the other maintained an increment 

of 24 to 29 mVha (343 to 414 ftVacre) 

until age 60 (Madsen 1977). 

The forest-management tables published by Hamilton and Christie 

(1971) seem to be the best summary 

of western redcedar productivity in 

Britain. They show that height 

growth of redcedar is slower than, 

that of Douglas-fir, western hemlock, or grand fir during the first 50 

years. It is sometimes faster than 

that of Sitka spruce, but only on 

poor sites. Dominant redcedars have 

larger diameters than other species 

at any given height. The volume production shown in table 6 exceeds 

that of Douglas-fir, grand fir, and 

Sitka spruce at heights of 20 and 

30 m (66 and 98 ft), but is less than 

that of noble fir. 

Where Hamilton and Christie (1971) 

present yields in terms of stand age 

rather than stand height, their normal yield tables show that cumulative volume production on good 

sites is lower for redcedar than for 

Douglas-fir, western hemlock, Sitka 

spruce, or grand fir - but only until 

age 20. For 60- and 80-year-old 

stands, cumulative production of 

redcedar equals that of western 

hemlock and exceeds the cumulative production of Douglas-fir or 

Sitka spruce on good sites. 

The average age of maximum mean 

annual increment is older for 

western redcedar than for Douglasfir, western hemlock, Sitka spruce, 

or grand fir on good sites. It is 

younger than western hemlock on 

poor sites, and younger than noble 

fir on all sites. 

An early article by Jackson and 

Knapp (1914) provided some site information on western redcedar in 

terms of “short trees,” “medium 

trees,” and “tall trees.” A preliminary site-class table for mature 

redcedars was published 34 years 

later (Province of British Columbia 

1948). Chambers and Wilson (1972) 

used total age and 100-year siteindex curves in developing yield 

tables for conifer stands of western 

hemlock, Sitka spruce, and western 

redcedar in western Washington. 

Differences in the shapes of 

heightlage curves for western hemlock and western redcedar are relatively small, but redcedars usually 

are shorter than hemlocks at a given 

age (see Smith et al. 1961a). The 

best available site-index curves for 

western redcedar appear to be the 

preliminary, polymorphic curves 

developed by Kurucz (1978) for 

coastal British Columbia (figs. 5 

and, 6). 

Height-age and diameter-age rela 

tionships for British Columbia 

redcedars were published by the 

British Columbia Forest Service 

(1948b). For example, a 15-cm (6-in) 

d.b.h. redcedar that is 40 years old 

may be expected to attain 44.5-cm 

(17.5-in) d.b.h. at 100 years and 

93.5-cm (36.8-in) d.b.h. at 200 years 

on a good site in coastal British Columbia. North coast redcedars on 

average sites required 18 years to 

reach a height of 10 feet (3 m) 

(British Columbia Forest Service 

1 948 b). The height -d i ame t e r re I at ionship determined by Brown et al. 

(1977) for western redcedars in Montana is: 

Height = -15.40 + 

18.80 (diameter)O.603? 

Slte 

Index 36 

33 

30 

21 

24 

21 

18 

15 

12 

0 10 M 50 40 M En m 80 90 rm 110 120 1YI 140 1M 160 

Brs.esbhelght age (yean) 

Figure 5. - Site index curves for western redcedar in coastal British Columbia (courtesy 

J.F. Kurucz, MacMillan Bloedel Limited). 

Slte 

index 123 

110 

IO0 

90 

80 

210 

ma 

190 

180 

110 

(En 

150 

140 

130 

m 

W 

120 50 

.E 110 

r 100 40 

.n 2 90 

80 

10 

bo 

50 

40 

30 

20 

10 

0 10 20 30 10 50 60 10 80 90 100 110 120 130 140 1.50 1s 

Bmast.heigh1 Age (years) 

Figure 6.-Site index curves for western redcedar in coastal British Columbia (courtesy 

J.F. Kurucz, MacMillan Bloedel Limited). 

41 
Height growth of western redcedars 

in southeastern Alaska may reach 

its maximum at an early age, and 

small-diameter trees tend to have 

higher Girard form-classes than 

large-diameter trees (Andersen 

1955b). Andersen’s form-class 

measurements ranged from 55 to 76 

for 9.8-m (32-ft) logs. Form-class 

measurements are greatly influenced by bark thickness. Bones 

(1962) found the average ratio of 

inside- to outside-bark diameters at 

the top of the first 4.9-m (16-ft) log of 

Alaska redcedar to be 0.9396. Formclass measurements have not been 

published as such for interior 

western redcedar, but butt-taper 

tables (Breadon 1957) are available. 

They permit conversion of diameters 

measured at 0.3, 0.5, 0.6, 0.8, 0.9, 1.1, 

1.2, 1.5, 1.8, 3.0, 3.7, or 5.2 m (1.0, 

1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, 6.0, 8.0, 

10.0, 12.0, or 17.0 ft) above ground to 

diameter at breast height. 

Western redcedar volume tables 

were included in Jackson and 

Knapp’s 1914 article and in Haig’s 

1932 tables for the western white 

pine type. Several others tables have 

been published since. A cubicvolume table for mature western 

redcedar in British Columbia listed 

gross merchantable volume for six 

site classes by 2-inch (5-cm) d.b.h. 

intervals (Province of British Columbia 1948). The British Columbia 

Forest Service (1949) also published 

site-class volume tables. Interim 

tables from the Pacific Northwest 

Forest and Range Experiment Station (1953) were superseded by the 

cubic- and board-foot tables in 

Agriculture Handbook 92 (Johnson 

1955). Those tables were based on 

measurements of interior western 

redcedar, however (table 7). The 

form-class volume tables published 

by Andersen (1955c, 19554) for 

cubic- and board-foot volumes of 

western redcedar in southeastern 

Alaska are more appropriate for 

coastal conditions. 

Constants listed by Smith and Ker 

(1957) for their volume equation, (V 

= a + b (D2H/100), included appropriate values for western redcedar in 

British Columbia. The British Columbia volume tables of Fligg and 

Breadon (1959) provided regionally 

applicable information by 32-foot-log 

position in the tree. Those of 

Browne (1962) included separate 

tables for interior and coastal redcedar in British Columbia, with the 

coastal volumes further segregated 

by mature and immature trees. 

Volume tables and equations for 

mature, old-growth redcedar were 

prepared by Farr and LaBau (1971) 

for southeastern Alaska (table 8). Immature redcedars managed for short 

rotations were used in deriving the 

volume equation published by Smith 

and DeBell (1973): 

V = 0.31 + 0.234D2H. 

Yield data for western redcedar furnished by Jackson and Knapp (1914) 

for the Puget Sound area appear to 

be more applicable to individual redcedar trees than to stands, and 

relating them to modern management practices might be difficult. 

The preliminary redcedar growth and 

yield data of Smith et al. (1961b) 

probably would be easier to apply, 

because they are sorted by stand 

density, age, and site index. Smith 

et al. assumed that the growth and 

yield of western redcedar are generally similar to the growth and yield 

of western hemlock. Chambers and 

Wilson (1972) also seem to have 

made this assumption in constructing empirical yield tables for western redcedar, western hemlock, and 

Sitka spruce in western Washington. 

42 
Table 7 - Volumes for western redcedar in the western white pine region' 

Total height of tree (feet) 

D. b. h. 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

- 

- 

- 

2.1 

3.2 

4.5 

6 

8 

9 

11 

14 

16 

18 

21 

24 

27 

30 

33 

36 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

2.5 

3.8 

5.3 

7 

9 

11 

14 

16 

19 

22 

25 

29 

32 

35 

39 

43 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

6 

8 

10 

13 

16 

19 

22 

25 

29 

33 

37 

40 

45 

49 

53 

58 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

7 

9 

12 

14 

18 

21 

25 

28 

33 

37 

41 

45 

50 

55 

60 

65 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

13 

16 

20 

23 

27 

32 

36 

41 

46 

50 

55 

61 

66 

72 

77 

83 

90 

96 

103 

110 

117 

125 

132 

- 

- 

- 

- 

- 

- 

14 

18 

22 

26 

30 

35 

40 

45 

50 

55 

60 

66 

72 

78 

84 

91 

98 

105 

113 

120 

128 

136 

143 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

29 

33 

38 

43 

49 

54 

60 

65 

71 

78 

84 

91 

99 

106 

114 

122 

130 

138 

146 

154 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

36 

41 

47 

53 

58 

64 

70 

77 

84 

91 

98 

107 

115 

123 

131 

140 

148 

157 

165 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

38 

44 

50 

56 

62 

69 

76 

83 

90 

98 

106 

115 

123 

132 

140 

149 

158 

167 

176 

'From Haig (1932), Johnson (1955). Volumes include stump, stem, and top. 

43 
Table 8 - Volumes for western redcedar in southeastern Alaska' 

Total height of tree (feet) 

D.b.h. 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 

Inches 

6 

8 

10 

12 

14 

16 

18 

20 

22 

24 

26 

28 

30 

32 

34 

36 

38 

40 

42 

44 

46 

48 

50 

52 

54 

56 

58 

60 

62 

64 

66 

68 

70 

3.2 

6.6 

10.6 

15.5 

21.2 

27.8 

35.3 

43.6 

52.7 

62.8 

73.7 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

3.6 

7.4 

1 1 .,9 

17.3 

23.7 

31.1 

39.4 

48.6 

58.9 

70.1 

82.3 

95.4 

110 

125 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

4.1 

8.2 

13.2 

19.2 

26.2 

34.3 

43.5 

53.7 

65.0 

77.4 

90.8 

105 

121 

138 

155 

174 

194 

21 5 

237 

260 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

14.4 

21 .o 

28.7 

37.5 

47.6 

58.8 

71.1 

84.7 

99.4 

115 

132 

151 

170 

191 

21 2 

235 

259 

285 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

15.7 

22.8 

31.2 

40.8 

51.7 

63.8 

77.3 

92.0 

108 

125 

144 

164 

185 

207 

23 1 

256 

282 

309 

338 

368 

399 

432 

466 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

24.6 

33.7 

44.0 

55.8 

68.9 

83.4 

99.3 

17 

35 

55 

77 

199 

223 

249 

276 

304 

334 

365 

397 

431 

466 

503 

54 1 

580 

62 1 

663 

706 

75 1 

797 

845 

- 

- 

- 

- 

- 

47.3 

59.9 

74.0 

89.5 

07 

25 

45 

67 

90 

21 4 

240 

267 

296 

326 

358 

392 

426 

463 

500 

540 

580 

623 

666 

71 1 

758 

806 

856 

907 

- 

- 

- 

- 

64.0 

79.0 

95.7 

114 

134 

155 

178 

202 

229 

256 

286 

31 6 

349 

383 

41 8 

456 

494 

535 

577 

620 

665 

71 2 

670 

81 0 

86 1 

91 4 

969 

- 

- 

- 

- 

- 

- 

- 

- 

- 

142 

165 

189 

21 5 

243 

273 

304 

337 

37 1 

407 

445 

485 

526 

569 

61 4 

660 

708 

757 

809 

862 

91 7 

973 

1031 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

175 

201 

228 

258 

289 

322 

357 

393 

432 

472 

51 4 

558 

603 

650 

700 

750 

803 

858 

91 4 

972 

1032 

1093 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

21 2 

24 1 

272 

306 

340 

377 

41 6 

456 

499 

543 

589 

637 

687 

739 

793 

849 

906 

966 

1027 

1090 

1155 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

287 

322 

359 

397 

438 

481 

526 

572 

62 1 

672 

724 

779 

836 

894 

955 

1017 

1082 

1149 

1217 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

338 

377 

41 8 

461 

505 

552 

602 

653 

706 

76 1 

81 9 

878 

940 

1004 

1069 

1137 

1207 

1279 

'From Farr and LaBau (1971). Volumes are based on a 1-ft stump and 4-in-top d.i.b. 

44 
Silviculture 

Seeding 

Western redcedar regeneration occurs after clearcutting in British Columbia and Alaska (Schmidt 1955, 

Harris and Farr 1974). Nevertheless, 

natural regeneration has not been 

relied on to achieve immediate and 

complete restocking of logged areas 

on Vancouver Island (see Hetherington 1965). A seed and sawdust 

mixture was broadcast on melting 

snow near Cowichan Lake in an 

early d irect-seedi ng trial (Brit ish Columbia Forest Service 1948a). Only 

2.5 percent of the redcedar seeds 

survived, but 1,235 seedlingslha (500 

seedlingslacre) were alive after two 

growing seasons. Isaac’s (1939) 

early work indicated probable success for broadcast seeding of 

western redcedar at rates of 5.4 to 

10.9 kglha (1 to 2 Iblacre) if it were 

done within 2 years of slash burning. Waiting longer than 2 years on 

Oregon’s Tillamook burn resulted in 

poor stocking of redcedar when the 

broadcast seeding was done in the 

spring (see Engstrom 1955). 

Trials of direct redcedar seeding in 

northern Idaho indicated that seed 

spots sown in the autumn resulted 

in better initial stocking than those 

sown in the spring (Schopmeyer 

1940, Helmers 1946, Schopmeyer 

and Helmers 1947). Protection from 

rodents was unnecessary when the 

seeds were covered with a thin layer 

of soil, but insufficient soil moisture, erosion, and smothering by 

leaves, bark, duff, and rotten wood 

were serious (McKeever 1942). Excellent 5th year stocking resulted 

when the redcedar seeds were sown 

on cutovers and broadcast-burned 

areas with stable soils and light or 

moderate covers of low vegetation 

(Helmers 1946). 

Nursery Practices 

Although western redcedars 

amounted to only a small fraction of 

their total production, approximately 

650,000 redcedar seedlings were produced by nurseries in Washington 

during 1977 (Bolsinger 1979). Redcedar has been grown in European 

nurseries for many years by several 

met hods. 

Redcedar seeds may be separated 

from the cones by kiln-drying at 

32°C (9O”F), shaking in a mechanical 

cone shaker, and fanning. They 

should not be dewinged (Schopmeyer 1974). Empty seeds are frequent in western redcedar cones. 

They may be separated from full 

seeds in an airstream (Schopmeyer 

1974) or by immersing in petroleum 

ether (Lebrun 1967). Western redcedar seeds are stored at - 18°C 

(0°F) in many western nurseries 

(Schopmeyer 1974). 

Seedbeds should be sown in the 

spring for best results (see Aldhous 

1967, Schopmeyer 1974). Sowing 

depths of 3 to 10 mm (118 to 318 in) 

and seedbed densities of 377 to 

1,076 seedlingslm2 (35 to 100 seedlingslft2) are commonly used. Halfshaded seedbeds are recommended 

during the first growing season 

(Schopmeyer 1974). Some European 

nurseries had better success with 

seedbeds of needle or leaf litter 

than with mineral soil (Hutt 1956, 

Rohrig 1958). Organic matter in the 

seedbed promotes the growth of 

Thelephora terres tris, how ever (We i r 

1921), and redcedar seedlings are 

usually grown in soil beds. Infrequent irrigation of nursery beds 

(“predroughting”) had no beneficial 

effect on western redcedar seedlings that were subsequently subjected to dry environments (see Oppenheimer 1967). Seedlings responded best to spring transplanting in Germany (Mormann 1956). 

Petroleum products have been used 

as nursery weedkillers. A French 

compound, Desherbant Carottes No. 

35,y damaged western redcedar 

seedlings more than those of the 

firs,, spruces, or pines (Bouvarel 

1951). Light petroleum was less 

damaging to redcedar than to 

Douglas-fir, Norway spruce, or the 

larches in Denmark (Petersen 1952). 

Redcedar was also resistant to the 

winter application of propyzamide in 

Britain (Brown and McKenzie 1974). 

Effective control of Didymascella 

thujina has been obtained by spraying cycloheximide fungicides on the 

affected nursery beds. The cycloheximide itself is more damaging to 

western redcedar than its oxime, 

semicarbazone, and acetate derivatives, however (Pawsey 1962a, 1965; 

Phillips 1962, 1964). Concentrat ions 

of 50 to 150 plm have been recommended for these derivatives. They 

were most effective when applied in 

the spring and summer (Pawsey 

1965). 

Western redcedar cuttings for use in 

silviculture may be produced easily 

and cheaply (Sqegaard 1956a). 

Sqegaard recommended July and 

August cuttings. Untrimmed cutt ings, treatment with indolebutyric 

acid in talc, and a sand-peat (75 

percent-25 percent) rooting medium 

heated to 21°C (70°F) were recommended by Matthews (1951). Misting 

the rooting bed with a nutrient mist 

fortified with 45 gl100 liters (6 oz/lOO 

gal) soluble 23-19-17 fertilizer improved cutting growth and nutrient 

content (Wott and Tukey 1965). 

‘OThe mention of products does not imply endorsement by the U.S. Department 

of Agriculture to the exclusion of other 

products that might be suitable. 

45 
Soluble fertilizers have been added 

to irrigation water in the production 

of containerized western redcedar 

nursery stock. The procedures 

described by Owston (1974) included 

frequent irrigation at pH 5.0 to 5.5 in 

a greenhouse. Owston’s redcedars 

were sown in mid-June in Styroblocksg filled with a peatvermiculite mixture, grown all summer in the greenhouse, and hardened-off in late October to midNovember. The seedlings were ready 

to plant in January and February. 

Unfortunately, containerized western 

redcedar seedlings have not survived as well as bare-root stock 

when planted in western Oregon and 

western Washington (see Owston 

1977). Planting has not been very 

successful in Idaho (Parker 1979). 

Nursery stock is frequently lifted 

when dormant, then kept in cold 

storage until field sites are ready to 

plant in the spring. Aldhous (1964) 

found western redcedar to be one of 

the least satisfactory species tested 

for survival after cold storage. His 

results were somewhat confounded 

by postplanting rainfall differences, 

however, and Aldhous included redcedar in only one experiment. 

Rapid emergence of western redcedar from dormancy may affect its 

survival after cold storage. In 

J a blanczy’s (1 964) ex per i ments with 

responses to photoperiod, western 

redcedar broke dormancy in 1 week. 

Western hemlock took about 4 

weeks, and Douglas-fir did not break 

dormancy until about the 7th week 

after the beginning of artificial illumination. 

~~ 

%tyroblocks are rectangular pieces of 

Styrofoam containing cavities in which 

tree seedlings are grown. 

Stand Culture and Improvement 

Natural even-aged stands of western 

redcedar seem to be relatively rare. 

Redcedar grows in even-aged stands 

on poor sites in southeastern 

Alaska, however (Gregory 1957), and 

even-aged redcedar plantations are 

occasionally established. Redcedar 

seedlings were planted at 0.3- by 

0.3-m (1- by l-ft) spacing in the lower 

Fraser River Valley and studied for 

15 years by Smith and DeBell (1973) 

to determine short-rotation yields in 

pure, dense stands. They were less 

productive than stands of Douglasfir, western hemlock, or black cottonwood when grown this way. 

The four small stands of almost 

pure, second-growth redcedar 

studied by Nystrom (1980) in western Washington were essentially 

even aged, and his reconstruction of 

their growth and development led to 

the following conclusions: 

Douglas-firs seem able to dominate western redcedars even if they 

become established 5 years later. 

Redcedars are rapidly overtopped 

by red alders, but they survive under 

an alder understory. 

On moist sites, dominant and intermediate crown classes are 

distinguishable by age 5 in western 

redcedar. Dominant and codominant 

classes can be identified by age 25. 

Stratification into crown classes occurs more slowly on dry sites. 

*On moist sites where crown class 

differentiation occurs early, height 

growth of redcedar is not noticeably 

affected by stand density. Diameter 

growth varies inversely with density. 

An initial stocking level of at least 

2,470 treeslha (1,000 treeslacre) will 

produce more volume by age 25 

than lower levels. After age 25, 

about 1,235 treeslha (500 treeslacre) 

with not more than 490 dominantslha (200 dominantslacre) may 

provide maximum volume growth. 

When grown in fully stocked, pure 

stands, the stem form of western 

redcedar is comparable to other 

western conifers. 

Nystrom suggested the establishment of 2,470 redcedarslha (1,000 

treeslacre) on site Ill (McArdle et al. 

196l), with a merchantable thinning 

to remove intermediates at age 25. 

The residual stand of 940 redcedar 

dominants and codominants per ’ 

hectare (380 per acre) could be 

crown-thinned thereafter. The ages 

of first thinning recommended by 

Hamilton and Christie (1971) range 

from 21 on good sites to 30 on poor 

sites in Britain. 

Mixed-species, uneven-aged stands 

with a western redcedar component 

are more common than pure stands. 

In the mixed-species stands of 

British Columbia, redcedar may furnish an interim pole crop that will 

provide financial help in carrying 

Douglas-fir and western hemlock to 

maturity (Gilmour 1945). In Idaho, 

well-established redcedars grow well 

in the understory if they have a 

reasonable amount of space (Watt 

1960). Redcedar has been underplanted successfully in the western 

white pine type of Idaho (Haig 1936), 

in Britain (Hubbard 1950), and under 

Scotch pine in East Germany (see 

Lembcke 1970). Interplanting was 

successful in the Podocarp forests 

of New Zealand (Hocking and 

Mayf ield 1939), where the redcedars 

were able to maintain their position 

with competing second growth and 

should furnish an early timber yield 

while the native natural regeneration 

is devoping to maturity (New 

Zealand Director of Forestry 1940). 

Small groups (“nests”) of western 

redcedar and other North American 

species were recommended by 

llmurzyhski et al. (1968) for the 

forests of Poland. 

Several elaborate trials of larchredcedar (Evans 1950, Jones 1964) 

and oak-redcedar (Keatinge 1947, 

46 
Jones 1964) mixtures were carried 

out in Britain. The larch-redcedar 

stands were two-storied with larch 

as the overstory. Western redcedar 

tended to form an overstory in the 

oak-redcedar stands, acting as a 

nurse crop. Jones (1964) found that 

British oaks grew taller than redcedars on wet ground where competition from other vegetation was 

extreme, creating a redcedar understory. 

Western redcedar understories seem 

capable of responding well to 

release after overstory removal 

(Leaphart and Grismer 1974) when 

the overstory is of another species. 

When both the overstory and understory are western redcedar, translocation through root grafts to cut 

stumps renders thinning from below 

more effective than thinning from 

above (see Eis 1972). The largest 

understory redcedars and those with 

least overstory competition usually 

respond best to overstory removal in 

the western white pine type 

(Leaphart and Foiles 1972). When 

that overstory is removed all at 

once, however, the initial increase in 

understory growth may be followed 

by redcedar chlorosis and root rot 

20 years later (Intermountain Forest 

and Range Experiment Station 1962, 

Koenigs 1969). Leaphart and Foiles 

(1972) found that gradual removal of 

the overstory worked better, stimulating growth of the redcedar understory without producing chlorosis or 

increasing root rot. Western redcedars released in Danish thinning 

trials had less lower stem taper and 

more upper stem taper than 

unreleased trees (Madsen 1977). 

Release through herbicide use is 

complicated by western redcedar’s 

susceptibility to dormant sprays of 

2,4-D and 2,4,5-T iso-octyl esters in 

diesel oil (Packee 1976). 

Taper and tree form of redcedar are 

profoundly influenced by stand density. From 1,976 to 2,470 treeslha 

(800 to 1,000 treeslacre) are needed 

to maintain good form and prevent 

“candelabra” growth of western 

redcedar on Vancouver Island, 

British Columbia (personal communication, Edmond C. Packee, MacMillan Bloedel Limited, Nanaimo, 

British Columbia). Unpruned western 

redcedars are valueless in New 

Zealand, but epicormic branching in 

open conditions makes pruning ineffective except in dense, dark stands 

(Weston 1971). Pruning did not 

cause rot or other defects in Norway, and the pruning season did not 

affect results (Bauger and Orlund 

1962). 

Fertilization with phosphorus and 

potassium improved western redcedar growth in Irish peat-bog plantations (Carey and Barry 1975). 

Small, often negative growth correlations were associated with the redcedar fertilization experiments of 

Smith et al. (1968) in British Columbia, ho’wever. The British Columbia 

fertilization had no obviously beneficial influence on production of 

redcedar cones. 

Harvesting 

As western redcedar is seldom 

found in pure stands within its 

native range, it is usually harvested 

with Douglas-fir, western hemlock, 

and other associated species (see 

McBride 1959). When partially cut, 

mixed stands in the interior wet belt 

of British Columbia gave the maximum economic return when western 

redcedar was cut to 30-cm (12-in) 

d.b.h., western white pine to 41 cm 

(16 in), and all other species to 36 

cm (14 in) in 1956 (Stewart 1956). 

Partial cutting is seldom used, however. Western redcedars cannot be 

left as scattered seed trees in 

coastal British Columbia, where 

even redcedars along clearcut 

margins may be lost to windthrow 

or exposure (Garman 1955). Most 

redcedars are harvested by 

clearcutting. 

Large quantities of slash are 

created in clearcut harvesting operations; western redcedar leaves more 

slash than other northwestern species (see Olson and Arnold 1959, 

Gockerell 1966). Tables of residues 

by individual tree and basal area 

prepared by Snell and Brown (1980) 

indicate that lower weights of sound 

slash are produced by redcedar 

than by Douglas-fir, grand fir, 

western hemlock, or ponderosa pine, 

however; the large quantities of 

slash probably result from the large 

amounts of cull and breakage 

associated with most redcedar 

harvesting. Breakage can be reduced 

by pulling large old-growth redcedars 

uphill (Guimier 1980). The additional 

directional felling costs are recovered 

through increases in harvested volume 

and improved log quality. 

When slash from decadent western 

redcedar-western hemlock stands 

was burned, a greater proportion of 

redcedar than of hemlock slash was 

consumed (Muraro 1971) - a result 

of greater longitudinal and horizontal fracturing of the redcedar. When 

fracturing is not a factor, fresh 

western hemlock slash is at least as 

flammable as western redcedar 

slash (see Olson 1953, Fahnestock 

1960). Fire spreads slower in hemlock when the slash from both 

species is 1 year old (Fahnestock 

1960); hemlock drops its foliage, 

redcedar does not. The slash of both 

species becomes less flammable 

when chipped (Fahnestock 1953). 

The fire hazard normally associated 

with cutting of redcedar poles was 

reduced by skidding entire pole-size 

trees to the landing, where the slash 

was chipped and blown over the 

edges (Olson and Arnold 1959). 

Chipping slash instead of burning it 

certainly reduces the fire hazard, but 

its effect on redcedar regeneration 

seems uncertain, and chipping is 

seldom practical. Although western 

redcedar can establish itself readily 

after logging with or without slash 

burning (Schmidt 1955), it seems to 

regenerate better after burning on 

the northern coast of British Columbia (British Columbia Forest Service 

1948b). Slash burning has little effect on species composition in the 

hemlock-cedar type of coastal 

British Columbia, however, and it 

may retard the successful conifer 

regeneration that usually occurs 

there (Stoodley 1925). Disturbance of 

the forest floor seems essential for 

natural redcedar regeneration (Clark 

1970). Slash burning probably is not. 

47 
Discussion Recommendations for 

Management 

The various subjects included in this 

report have not been equally discussed. Relative length and detail 

included in each section were determined by the amount of information 

available, not by their importance. 

For example, the section on products is twice as long as the section 

on silviculture; this inequality seems 

particularly important. Western redcedar wood is a highly valued, intensively used product that has been 

studied in great detail. Unfortunately, much less time, money, and 

effort seem to have been invested in 

learning how to grow the wood. 

More information is needed on site 

evaluation, nursery culture, planting 

techniques, fertilization, optimum 

stand densities, thinning of redcedar, and management of mixed 

species. Trees with desirable annual 

ring widths, knot characteristics, 

and forms might even be grown to 

order if the silviculture of redcedar 

were truly understood. 

A true understanding of silviculture 

rests on foundations of physiology, 

ecology, genetics, mensuration, and 

economics. Adequate knowledge 

about western redcedar is lacking in 

all five categories. For example, the 

relation of moisture to redcedar 

regeneration and growth should be 

further investigated. So should its 

growth on various sites - sites that 

are objectively described and defined. The breeding of superior redcedar planting stock has scarcely 

begun. Accurate local volume tables 

and yield information are scarce, as 

are comparative economic analyses 

of mixed- compared with pure-stand 

culture and redcedar rotation 

lengths. 

Redcedar rotations do not seem to 

have been seriously considered 

apart from the rotations of associated species. Indeed, redcedar 

timber often has been managed like 

a valuable mineral that is mined 

when found in association with 

other minerals or reclaimed from old 

mine tailings (i.e., logging residues 

of former years). Utilization technology is advanced, but redcedar 

usually has been removed, refined, 

manufactured, and managed as a 

declining, nonrenewable resource. 

Western redcedar is a renewable 

resource that need not decline. It 

can be renewed and used forever, as 

are several other tree species now 

being planted and managed intensively. More research on the culture 

of redcedar and a different management philosophy may be necessary, 

however. Western redcedar differs 

from Douglas-fir or western hemlock, and it should be managed differently - not as just another associated species, but as a major 

timber crop. 

The techniques used to manage 

other major timber crops are often 

inappropriate for western redcedar, 

but few techniques have been 

developed for redcedar. Management recommendations are based 

on the site, regeneration, growth, 

yield, tolerance, and longevity information in this report. As they have 

not been applied in a coordinated 

redcedar management program, they 

should be considered plausible suggestions rather than guidelines. 

Western redcedar management 

sites should be chosen with care. 

Moist, fertile conditions characterized by the presence of Athyrium 

filix-femina, Clintonia uniflora, 

Dryop teris a us tria ca, Gym no ca rpium 

dryopteris, and Rubus pawiflorus 

are best. 

Redcedar probably should be 

grown in pure stands when sawtimber, shingles, or shakes are the 

desired products. Even-aged mixtures of redcedar and other conifers 

will be harvested either too early for 

the redcedar sawtimber or too late 

for the other conifers when mixedspecies, even-aged stands are clearcut. 

Redcedar can be grown in mixed 

stands when poles are to be produced under even-aged management 

regimes. 

e Redcedar is suitable for unevenaged management, either in pure or 

mixed stands. Vegetative regeneration probably will be more efficient 

than sexual regeneration where the 

selection system is practiced. 

Direct seeding with redcedar is 

practical and effective where a 

mineral soil seedbed is available. 

Rates of 5 to 10 kglha (1 to 2 Iblacre) 

seem appropriate for broadcast 

seeding. The seeds should be 

covered with a thin layer of soil 

when seed spots are used. Sowing 

should be done in the fall. 

48 
Acknowledgment 

Where mineral soil seedbeds are 

not available, planting may be effective. Recently lifted, bare-root stock 

should be used, and cold storage 

should be avoided. 

Michael E. Dubrasich, formerly 

forestry technician, searched much 

of the literature summarized here. 

Redcedar plantations should be 

dense, with 1.2- to 1.5-m (4- to 5-ft) 

spacing between seedlings. 

Where pure, even-aged stand 

management is practiced, intermediate crown classes should be 

removed in a light thinning at about 

age 30. A nearly closed canopy 

should be maintained at all times, 

however; open-grown redcedars tend 

to develop poor form, excessive 

limbs, and multiple tops. 

Where western redcedar is managed in mixed-species or unevenaged stands, its shade tolerance 

and long life should be considered. 

Redcedars will tolerate understory 

conditions in mixed-species stands. 

In uneven-aged stands, they should 

maintain acceptable growth rates 

over long periods. Excessive crown 

space should be avoided under all 

management regimes. 

49 
Common and Scientific Names of Trees 

Common Name 

Alaska-cedar 

A I p i ne-as h 

Austrian pine 

Baldcypress 

Big leaf maple 

Birch 

BI ac k cottonwood 

Brisbane boxwood 

California-lauqel 

Cascara buckthorn 

Chinkapin 

Douglas-f i r 

Eastern redcedar 

Eastern white pine 

Engelmann spruce 

European beech 

European larch 

European white birch 

Grand fir 

Incense-cedar 

Japanese larch 

King-Wil liam-pine 

Larches 

Lodgepole pine 

Longleaf pine 

Monterey pine 

Mountain hemlock 

Noble fir 

Northern whit e-ced ar 

Norway spruce 

Oak 

Oregon white oak 

Pacific dogwood 

Pacific madrone 

Pacific silver fir 

Pacific yew 

Paper birch 

Pi ne 

Ponderosa pine 

Port-or ford-cedar 

Quaking aspen 

Red alder 

Red oaks 

Red pine 

Redwood 

Scotch pine 

Shore pine 

Sitka spruce 

Southern yellow pines 

Spruce 

Subalpine fir 

Sugar pine 

Tamarack 

Tanoak 

Walnut 

Western hemlock 

Western larch 

Western redcedar 

Western white pine 

Whitebark pine 

White spruce 

Scientific Name 

Chamaecyparis nootkatensis (D. Don) Spach 

Eucalyptus delegatensis R. T. Baker 

Pinus nigra Arnold 

Taxodium distichurn (L.) Rich. 

Acer macrophyllum Pursh 

Betula L. sp. 

Populus trichocarpa T. & G. 

Tristania conferta R. Br. 

Umbellularia californica (Hook. & Am.) Nutt. 

Rhamnus purshiana DC. 

Castanopsis chrysophylla (Dougl.) DC. 

Pseudotsuga menziesii (Mirb.) Franco 

Juniperus virginiana L. 

Pinus strobus L. 

Picea engelmannii Parry 

Fagus sylvatica L. 

Larix decidua Mill. 

Betula alba L. 

Abies grandis (Dougl.) Forbes 

Calocedrus decurrens (Torr.) Florin 

Larix kaempferi Sarg. 

Athrotaxis selaginoides D. Don 

Larix Mill. spp. 

Pinus contorta Dougl. 

Pinus palustris Mill. 

Pinus radiata D. Don 

Tsuga mertensiana (Bong.) Carr. 

Abies procera Rehder 

Thuja occidentalis L. 

Picea abies Karst 

Quercus L. sp. 

Quercus garryana Dougl. 

Cornus nuttallii Aud. 

Arbutus menziesii Pursh 

Abies amabilis (Dougl.) Forbes 

Taxus brevifolia Nutt. 

Betula papyrifera Marsh. 

Pinus L. sp. 

Pinus ponderosa Dougl. ex Laws. 

Chamaecyparis la wsoniana (A. Murr.) Parl. 

Populus tremuloides Michx. 

Alnus rubra Bong. 

Quercus falcata Michx. and Q. rubra L. 

Pinus resinosa Ait. 

Sequoia sempervirens (D. Don) Endl. 

Pinus sylvestris L. 

Pinus contorta Dougl. var. contorta 

Picea sitchensis (Bong.) Carr. 

Pinus caribaea Morelet, P. echinata Mill., 

P. palustris Mill., and P. taeda L. 

Picea A. Dietr. sp. 

Abies lasiocarpa (Hook.) Nutt. 

Pinus lambertiana Dougl. 

Larix laricina (Du Roi) I. Koch 

Lithocarpus densiflorus (Hook. & Arn.) Rehd. 

Juglans L. sp. 

Tsuga heterophylla (Raf.) Sarg. 

Larix occidentalis Nutt. 

Thuja plicata Donn 

Pinus monticola Dougl. ex D. Don 

Pinus albicaulis Engelm. 

Picea glauca (Moench) Voss 

50 
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properties, Soil Sci. SOC. Am. Proc. 

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Andersen, H. E. 

1955c. Preliminary western redcedar 

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Bannan, M. W. 

1951. The annual cycle of size 

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Aldhous, J. R. 

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Minore, Don. 

1983. Western redcedar: A literature review_. USDA For. Sew Gen. 

Tech. Rep. PNW-150, 70p. Pac. Northwest For. and Range Exp. 

Stn., Portland, Oreg. 

This report is a comprehensive compilation of information on 

western redcedar (Thuja plicata Donn) - its occurrence and abundance; associated plant species; morphology and anatomy; products; medical aspects; diseases; insect, bird, and mammal pests; 

genetics; ho rt i cu It u re; physiology; eeo logy; me nsu ration ; and 

silviculture. Management recommendations and an extensive list of 

references are included. 

Keywords: Western redcedar, Thuja plicata, silviculture, ecology, 

physiology, products. 
The Forest Service of the U.S. Department of 

Agriculture is dedicated to the principle of multiple 

use management of the Nation’s forest resources 

for sustained yields of wood, water, forage, wildlife, 

and recreation. Through forestry research, 

cooperation with the States and private forest 

owners, and management of the National Forests 

and National Grasslands, it strives - as directed by 

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