1
Contents

6.1.1 Introduction 3

6.1 .1 .1 Propagation methods 3

Seed propagation 4 

Vegetative propagation 4

6.1.1.2 Stocktypes and the target seedling 6

6.1.2 Seedling Growth and

Development 8

6.1 .2.1 Seed germination and emergence 8

6.1.2.2 Patterns of shoot growth 8

First-season shoot development 9 

Second-season shoot development 9

6.1.2.3 Annual growth cycles 10

6.1.2.4 Nursery growth phases 11 

Establishment phase 11 

Rapid growth phase 12 

Hardening phase 12

6.1.3 Constructing a Propagation

Protocol 14

6.1.3.1 Sources of propagation information 14

Systematically search the published 

literature 14

Compare propagation methods for related 

species 14

Study the native environment and natural growth 

habit of the plant 14

Consult with other nurseries growing the same or 

similar species 14

6.1.3.2 Growing schedules 17

Crop production schedules 17

Facilities schedules 18

Cultural schedules 20

6.1.3.3 Collection and preparation of propagules 23

6.1.3.4 Scheduling seedling growth phases 23

6.1 .3.5 Testing and adjusting protocols 23

6.1.4 Summary 25

6.1.5 References 26

6.1.5.1 Literature cited 26

6.1.5.2 General propagation references 27

Appendix A--Propagation

Protocol Form 28

Appendix B--Crop Production

Schedule Form 29

Appendix C--Facilities Schedule

Form 30

Appendix D--Cultural Schedule

Form 31

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6.1.1 Introduction

Plant propagation is both science and art. In this chapter, we will 

discuss the science of plant propagation, which requires a 

knowledge of plant physiology, nursery cultural practices, and 

characteristics of the particular plant that we want to grow. The art 

of plant propagation cannot be taught in a book or classroom, 

however, because it consists of specific technical skills that must be 

acquired through innate ability or experience and often requires a 

certain "feel." Good plant propagators are said to have a "green 

thumb." Successful propagators must be able to reproduce the 

desired crop species both consistently and economically. Although 

nursery managers can always hire growers or propagators with 

these skills, they themselves must also be familiar with the basic 

terminology and techniques of plant propagation.

The previous five volumes of this series showed how to construct 

the propagation facility and gather supplies for growing that first 

crop. In this volume, we review the sequence of processes and 

operations used to propagate container seedlings. Successful 

nursery management begins with planning. Crop planning is one of 

the most important, yet often neglected, aspects of seedling culture. This chapter discusses factors that must be considered during

crop planning and introduces concepts of propagation protocols 

and planning calendars called growing schedules.

6.1.1.1 Propagation methods

The first phase of the planning process is to determine which type of 

propagation method should be most effective and economical for 

the crop species. Both the biology of the species and the objectives 

of the outplanting project must be considered (figure 6.1 .1 A). Most 

commercially important tree species used in reforestation can be 

grown from seeds, but some ecologically important species must be 

produced vegetatively. A few trees used for timber or fiber are 

vegetatively propagated on a large-scale to multiply "clones" that 

have selected for specific traits such as fast growth. In the past 

decade, there has been increasing interest in the propagation of 

non-commercial native plants. One of the fascinating aspects about 

working in forest and conservation nurseries is that some native 

plants provide unusual propagation challenges (figure 6.1 .1 B)

If it is possible to propagate a plant either by seed or vegetatively, 

then the amount of genetic variability that is desired in the crop must 

be considered (figure 6.1 .1 A). Sexual reproduction results in a 

mixture of genetic characteristics in the offspring, so each plant will appear slightly different 

from its parents and each other (figure 6.1 .2). Because 

maintenance of genetic diversity is so important in ecosystem 

management, seed propagation is

3
Availability of propagation material, time constraints, and economics 

must be considered (figure 6.1 .1 A). Some species--such as 

western larch- produce ample seed crops very irregularly, so it may 

be impossible to obtain enough seed in time for an outplanting 

project. This is especially true for emergency projects, such as fire 

rehabilitation, when crops must be grown in a very short time. Seed 

propagation is almost always less expensive than vegetative 

propagation, because all vegetative propagation techniques involve 

more hand labor compared to seed propagation and many require 

special equipment and structures.

4

encouraged whenever possible because it is easier to capture and 

preserve biodiversity with seeds than with vegetative propagation. 

At the present time, most commercially important tree species used 

in reforestation are grown from seeds, because it is difficult to 

propagate them vegetatively.

Seed propagation. There are several options when choosing 

seed propagation (figure 6.1 .1 A). Direct sowing is the traditional 

method and consists of placing seeds directly into the growth 

container and allowing them to germinate in place (Hartmann and 

others 1997). Seedlings either can be allowed to grow to shippable 

size or transplanted into larger containers (container transplants) 

or soil beds in a bareroot nursery (plug transplants). Sowing

seeds into shallow trays, keeping them moist, and then planting 

germinants (germinating seeds) into growth containers is a 

second option. Transplanting emergents consists of sowing 

seeds into shallow trays and allowing them to germinate and the 

seedlings to emerge. The young "emergents" are then 

transplanted into the growth container to finish their development.

Each of these seed propagation techniques will be needed to 

propagate certain forest and conservation species. More 

information on seed propagation, including a detailed discussion of 

advantages and disadvantages of the various techniques, is given 

in chapter 2 of this volume.

Vegetative propagation. Although they vary considerably in 

technique, all vegetative propagation options (figure 6.1.1 A) are a 

form of asexual reproduction. The objective is to make multiple 

"copies" of an individual plant or select group of plants with similar 

genetic composition (Hartmann and others 1997). Species that root 

easily can be propagated with cuttings. This process involves 

collecting stem sections, treating the lower part with rooting 

hormones, and then either sticking them in trays filled with growing 

medium until they form roots or "direct sticking" them into the growth 

container. Layering consists of inserting a section of stem or root 

still attached to the plant into a favorable rooting environment until 

roots develop. The rooted section is then cut from the parent plant 

and transplanted into the growth container. Grafting is a very 

specialized propagation technique in which shoots or buds from one 

plant are surgically implanted into another. The newest and most 

rapidly developing vegetative propagation technique is 

micropropagation. This involves a series of sterile laboratory 

techniques in which small sections of plant tissue are chemically 

stimulated to form multiple shoots and are then rooted. The 

resultant "explants" are transplanted to growth containers and 

raised under normal culture. Vegetative propagation techniques 

vary considerably in effort and cost and a detailed discussion of 

their advantages and disadvantages is provided in chapter 3 of this 

volume.
5

Some species can be propagated either by seeds or vegetatively, 

and the decision depends on the objective of the outplanting project. 

Fraser fir, a native conifer that has a restricted natural range in the 

Southern Smoky Mountains, has become a highly prized Christmas 

tree (Blazich and Hinesley 1994). So, if the propagation objective is 

revegetation, then seed propagation would be the logical choice 

using seeds collected from the local seed zone. On the other hand, 

if the objective is Christmas trees, then propagation by stem cuttings 

from a cultivar selected for its desirable foliage color and crown form 

would be necessary. Quaking aspen (figure 6.1 .3A) is another good 

example of how the choice of propagation method depends on the 

objective. Aspen seeds are very small and difficult to handle 

because they are enclosed in a ball of cottony material (figure 6.1 

.3B). Seeds can be cleaned relatively easily, but usually are sown 

manually into growth containers because of their small size (figure 

6.1 .3C). Some nurseries sow seeds into germination flats and then 

transplant the young seedlings after they emerge (figure 6.1 .3D). If 

the objective is to retain the physical characteristics of a specific 

ecotype or clone, however, then aspen can be propagated vegetatively from root sprouts (figure 6.1 .3E), which are rooted and then 

transplanted to growth containers.
6.1.1.2 Stocktypes and the target seedling

The term stocktype is used to describe distinct categories of 

seedlings based on age, size, propagation method, and even 

delivery date. A wide variety of different stocktypes can be produced 

in container nurseries. Most seedling stocktypes are grown in 

containers for the entire crop rotation, whereas transplants are 

started in small-volume containers and then transplanted for another 

period of growth, either into larger containers or bareroot nursery 

beds (figure 6.1AA).

Stocktypes are typically described with numerical codes that refer to 

the type of container in which they were grown, but the system 

varies between regions. For example, in the western United States, 

a "Styro 4" refers to a seedling that has been produced in a 

Styrofoam® block container with cells that are approximately 65 cm3 

(4 ins) in volume. In British Columbia, this same stocktype would be 

called a "PSB 313B 1+0", meaning that this seedling was grown for 

1 year in a Styrofoam® block container that has cells that are 3 cm 

(1 .2 in.) wide and 13 cm (5.1 in.) deep (BC Ministry of Forests 

1998). Container transplants are described by the number of years 

in the bareroot nursery-for example a plug-plus-one (P+1) transplant 

would have been grown for 1 additional year. A major problem with 

any of the current stocktype naming systems is that seedlings of 

varying size and quality can be grown in the same size container 

and so a Styro 4 from nursery A may be significantly different than a 

Styro 4 from nursery B.

The stocktype name may also include the season of outplanting--

spring, summer, or fall. Because they can control seedling 

morphology and physiology, container nurseries can produce 

stocktypes for a wide variety of outplanting seasons and sites. The 

morphological, physiological, and genetic characteristics of 

seedlings should be targeted for individual outplanting sites, and the 

best stocktype for a site will depend on the biological demands of 

the site (McGilvray and Barnett 1982). There is no one ideal type 

of seedling that can be used for all purposes. The ultimate 

measure of seedling quality is performance on the outplanting 

site--both initial survival and early growth. (See section 1.1.1 

and figure 1.1.3 in volume one of this series for more discussion on 

stocktypes.)

Recently, growth after outplanting has been receiving more 

attention because some existing stock standards result in 

seedlings that survive satisfactorily but fail to

6

thrive, resulting in plantations that are not satisfactorily stocked or 

exhibit poor growth. This has led to the establishment of new 

"free-to-grow" standards that specify larger seedlings that are better 

able to successfully compete and grow after outplanting (Bowden 

and Scagel 1994; Wood 1994).

Both the seedling user and nursery manager are jointly responsible 

for successful plantations, and so must work together to define the 

best type of seedling for a particular planting project (Rose and 

others 1990). The seedling user must specify the proper genetic 

origin for the seedlings (for example, seed source), the type of outplanting tool, and which environmental factors on the outplanting 

site will be most limiting to survival and growth. By jointly agreeing 

on which morphological characteristics (for example, height, stem 

caliper, root volume) and physiological characteristics (for example, 

dormancy status, cold hardiness) will be needed to maximize 

outplanting performance for that particular site, the proper stocktype 

can be selected--the target seedling (figure 6.1.4).

The seedling buyer and the nursery manager should discuss the 

desirable morphological and physiological characteristics of the 

target seedling during the planning process and define 

specifications for that particular crop. The nursery manager can 

then design growing schedules to produce that crop in the shortest 

time and at the lowest cost. For example, target seedling 

specifications for reforestation sites in Alberta, Canada consist of 

four size- classes for white spruce and three for lodgepole pine 

(table 6.1.1). Each size class is defined by a target height and stem 

diameter and can be produced in various sizes of containers or as 

container transplants (Wood 1994). Another excellent discussion of 

how to select the proper target seedling in Ontario is given in the 

book Artificial Regenerations of Ontario's Forests: Species and 

Stock Selection Manual (Johnson and others 1996).

The effect of nursery culture on target seedling specifications is 

illustrated by the relationship between seedling size and container 

type-seedling size increases with container volume and spacing 

(figure 6.1.5). For example, to produce a specific size-class of 

white spruce, a nursery manager would select a container and 

design a growing schedule that would best meet the biological 

requirements of the species (see volumes 1 and 7 for further 

discussion on stocktypes).
7

To develop effective growing schedules, growers must consider 

how cultural practices affect various phases of seedling growth 

and development.
6.1.2 Seedling Growth and Development

Before nursery managers can raise a crop of seedlings, they must 

have a basic understanding of how seedlings grow and develop 

because propagation environments and cultural techniques affect 

the morphology and some times the saleability of the stock. Seedling 

growth and development is controlled by genetics and environment, 

whether in nurseries or in the wild. Environment has a proportionally 

greater effect in nurseries, however, where many or all potentially 

growth-limiting factors are kept at optimum levels. Because of this 

overriding environmental effect, container seedlings grow and 

appear differently than their wild counterparts in both amount and 

type of growth.

6.1.2.1 Seed germination and emergence

During seed germination, the root system begins growth first, when 

the radicle penetrates the seed coat and begins to extend 

downward under the influence of gravity (geotropism). After the 

radicle becomes established in the growing medium, the seedling 

follows either of two patterns of seed germination (Kozlowski 1971). 

Most conifers and some broadleafed species exhibit epigeous 

germination, in which the cotyledons ("seed leaves") are pushed 

above the surface of the growing medium by the expanding 

hypocotyl (figure 6.1.6A). Conifer cotyledons carry the seedcoat on 

their tips to form a "birdcage." Other broadleaved species, such as 

oaks, exhibit hypogeous germination, in which the cotyledons 

remain

underground while the epicotyl ("shoot') elongates upward and 

produces primary leaves above the surface of the growing medium 

(figure 6.1.6B). Some genera, such as Prunus spp., contain some 

species that have epigeous germination and others with 

hypogeous germination (Schopmeyer 1974).

6.1.2.2 Patterns of shoot growth

The way in which a seedling shoot grows is complicated and can be 

confusing because different terms have been used in the literature. 

We prefer the practical terminology used by Powell (1982), which 

recognizes two types of shoot growth. Preformed ("predetermined") 

growth is a result of the expansion of preexisting structures: either 

those preformed in the embryo for first year shoots or those in 

terminal and lateral buds in subsequent years. Neoformed ("free") 

growth, on the other hand, does not depend on any preformed 

structures but is instead determined by genetics and environment 

(figure 6.1.7). Some species exhibit both preformed and neoformed 

shoot growth in a given year, whereas others only have one or the 

other. This tendency is genetically determined and cannot be 

changed by cultural means (MacDonald 1998).

The presence or absence of buds also affects shoot terminology 

(Kozlowski 1971). The shoots of many temperate zone species, 

including spruces, form buds at the end of

8
the growing season (determinate shoots), whereas other 

species, such as junipers, do not (indeterminate shoots).

First-season shoot development. Seedling growth and 

development is different during the first growing season than in 

subsequent years because all species exhibit both preformed and 

neoformed growth (figure 6.1.8). In the first season, the amount of 

preformed growth is determined by the size of the embryo (which is 

preformed in the seed), the stored energy in the seed, and the 

germination environment.

Seedlings may or may not develop typical buds at the end of the 

first growing season. The shoots of determi nate species cease 

growth and form ("set") terminal buds (figure 6.1.8A/D). Other 

indeterminate species, however, never do form true dormant buds 

(figure 6.1 .813/C). The shoots of pine seedlings, in particular, can 

look remarkably different during the first growing season, depending 

on species and growth environment. There are at least 4

variations in shoot development in pines (Powell, 1982; Thompson 

1989). Some pines produce only awl-shaped primary foliage and, 

instead of a true bud, form a rosette of needles at the end of the first 

growing season (figure 6.1 .8C). Other pines produce fascicled 

secondary needles in the axils of the primary needles and form a 

typical resting bud (figure 6.1 .8D). In some temperate zone pines, 

the time of budset is under strong genetic control and the shoot will 

not continue to extend even under the ideal growing conditions in a 

fully controlled greenhouse (Thompson 1989). For example, 

ponderosa pine seedlings typically set a firm terminal bud in early 

July even though they are growing in a greenhouse under long-day 

photoperiod and high fertilization. In other species, such as blue 

spruce, shoot growth will continue for over a year under ideal 

growing conditions before forming a bud (Young and Hanover 

1978). Growers must induce budset in these species by radically 

changing the propagation environment. Ecotypes from northern latitudes are particularly prone to free growth during the long days of 

summer, and growers need to use extraordinary cultural measures 

such as blackout curtains to promote budset and dormancy. Bud 

development is particularly important because the presence and 

size of buds are considered by many customers to be a sign of 

seedling quality (more discussion on bud development and its effect 

on quality can be found in section 6.4.4 of this volume).

The shoot growth of broadleaved species is also variable under 

nursery conditions. In oaks, a temporary resting bud with scales 

may form between several growth spurts and a firm dormant bud is 

only formed at the end of the season. Leaf size and shape will also 

change between these growth spurts, with those formed later being 

larger and more deeply lobed (Powell 1982). In other indeterminate 

species such as birch and elm, however, a true terminal bud never 

forms (figure 6.1.813). Instead, the shoot tip aborts at the end of the 

season and a lateral bud functions as the new terminal bud 

(Kozlowski 1991).

The "take-home message" here is that the type of propagation 

environment has a profound effect on seedling growth patterns and 

that some cultural practices, especially photoperiodic lighting, will 

affect both the amount and type of shoot growth in the nursery. 

(This will be discussed in detail in section 6.4.4 of this volume.)

Second-season shoot development. If seedlings are held for a 

second growing season (a 2+0 stocktype), some species will 

produce only preformed or neoformed shoot

9
growth, whereas others will produce both types in sequence (figure 

6.1.7). Determinate species, such as pines, exhibit the former 

growth pattern as their entire second-season shoot extension 

comes from either preformed stem units in the dormant bud, resting 

rosettes, or long- shoot buds (Powell 1982). Shoot growth in other 

indeterminate species including junipers and birches does not 

depend on preformed structures from the first growing season but 

consists of only neoformed growth. Spruces and basswood 

seedlings exhibit both preformed and neoformed growth, with the 

amount of neoformed growth strongly controlled by ecotype (Von 

Wuehlisch and Muhs 1991).

10

6.1.2.3 Annual growth cycles

In the wild, seedlings of forest and conservation species follow a 

typical annual growth cycle. This cycle begins when seeds 

germinate or seedlings break dormancy in early spring and 

continues until the seedlings go dormant again in the fall. These 

same growth cycles occur in nurseries, but the timing of the various

phenological events depends on sowing date and the type of 

propagation environment. Usually, only shoot height and stem 

caliper are monitored, because these measurements are easy to 

record and are non-destructive. Some nurseries also sample 

seedlings during the growing season to
obtain ovendry weight, which allows the plotting of seedling 

biomass and root growth over time.

These seedling growth cycles can be graphed in 2 ways: total 

growth and incremental growth. The total growth curve is the 

most commonly used graphing method and shows seedling 

dimensions plotted against time throughout the growing season 

(figure 6.1.9). Total growth curves are useful for showing seedling 

growth progression relative to the target specifications of shoot 

height and stem diameter. The relative growth rate is illustrated by 

the slope of the line-the steeper the slope of the curve, the faster the 

seedling is growing. The other, less- common type of growth curve is 

the incremental growth curve, which plots growth rate, rather than 

total growth (figure 6.1.10). Incremental growth curves are useful 

because they reveal growth periodicity patterns (seedling growth 

monitoring is also discussed in section 1 .5.4 of volume one of this 

series).

Roots start to grow first after seed germination as well as for older 

seedlings. For new sowing, shoot growth begins with emergence or 

with bud break for older stock (figure 6.1 .10). Stem diameter 

(caliper) growth in newly germi nated seedlings begins after the 

vascular cambium develops and starts producing wood cells at 

about 4 to 6 weeks of age (MacDonald 1998). In older seedlings, 

stem diameter growth begins early in the spring, slowly increases 

until it peaks after terminal bud set, and then gradually tapers off 

until cold weather induces dormancy.

Note that there is competition between the shoot and root for 

photosynthate, and so an increase in shoot growth causes a 

relative decrease in root and cambial growth (figure 6.1.10). All 

seedlings follow this same general pattern, although the growth 

rate varies between different species.

6.1.2.4 Nursery growth phases

For planning purposes, seedling growth and development under 

nursery culture can be divided into consecutive growth phases. 

Although up to seven different phases have been used, we prefer 

only three: the establishment, rapid growth, and hardening 

phases. The relative duration of these phases is illustrated in 

figures 6.1.9 and 6.1.10. Nursery managers must have a detailed 

cultural plan for each phase that will achieve their objectives (van 

Steenis 1993; Wood 1994). Because cultural objectives are different 

for each phase, the growing environment and perhaps even the 

type of propagation structure also will be different. The amount of 

time required for each of these growth phases will vary depending 

on species, seed source, type of propagation environment, and 

cultural practices. Nursery managers use growth data from previous 

crops to estimate the duration of each phase and total length of the 

crop cycle.

Establishment phase. In the case of seed propagation, the 

establishment phase begins when seeds are sown, continues 

through seed germination and emergence, and ends when the 

young seedlings develop true leaves. For vegetative propagation, 

the phase begins when the cuttings are stuck into the container and 

ends when cuttings have rooted and the shoots begin to grow. For 

planning purposes, the establishment phase can be divided into the 

following 2 stages.

Germination stage. The germination stage begins when seeds are 

sown and lasts until the young seedlings form cotyledons. 

Germination and emergence should be completed in about 14 to 21 

days; if not, either the seeds have not been properly prepared or 

are of poor quality. Temperature and moisture stress are critical 

during this stage, and growers must also be particularly vigilant for 

disease and abiotic injury.

Early growth stage. This stage begins when seedlings have 

emerged and continues until shoots begin rapid growth; it can 

last for 4 to 8 weeks. Often, seedlings exhibit a short growth 

pause while rosettes of primary needles form above their 

cotyledons, and then shoot

11
growth continues. The primary foliage of some species, including 

pines and eucalyptus, is different in shape, size, and color 

compared to mature leaves. The seedling exhibits rapid root growth 

during the early growth stage, with lateral roots forming after the tap 

root reaches the bottom of the container and stops growing ("air 

pruning"). (Further discussion of the cultural procedures and propagation environment for the establishment phase is provided in 

chapter 4 of this volume.)

Rapid growth phase. The rapid growth phase is so-named 

because it is during this period that young seedlings increase rapidly 

in size; the bulk of this biomass increase is in shoot tissue with stem 

diameter and root growth relatively less (figure 6.1.10). This phase 

begins after the cotyledon stage when the new shoot begins to grow 

at an accelerated or exponential rate, and ends when the seedling 

has reached its target height (figure 6.1.9). In determinate species, 

this occurs when the terminal bud is formed ("set"); in indeterminate 

species, no bud is formed and the achievement of the target height 

is the only visible indication. The duration of the rapid growth phase

can vary considerably, but it typically takes from 10 to 20 weeks. 

This time, however, is a function of sowing date, desired target 

height, species characteristics, and especially propagation 

environment.

12

Therefore, it is critical to maintain all environmental factors near 

optimum levels. For example, shoot growth of many temperate 

zone species is particularly sensitive to photoperiod ("daylength") 

and will abruptly cease and form a terminal bud if photoperiod 

lights cease functioning for even a single night. (The rapid growth 

phase is discussed in detail in chapter 4 of this volume.)

Hardening phase. The hardening phase is the period of time in 

which the seedling diverts energy from shoot growth to stem 

diameter and root growth (figure 6.1 .10) and also becomes 

gradually conditioned to withstand the rigors of harvesting, shipping, 

and outplanting. The cultural objective here is to stop shoot growth, 

initiate development of a terminal bud in determinate species, and 

gradually bring the seedling into dormancy. This is accomplished by 

changing four environmental factors: lowering temperature, inducing 

mild moisture stress, reducing photoperiod, and changing 

fertilization rates and mineral nutrient ratios. Seedlings reach their 

target stem diameter during the hardening phase (figure 6.1.9), 

lateral buds are set, and root growth continues until a firm plug is 

formed. The hardening phase has two different but physiologically 

related cultural objectives that must be achieved in two sequential 

stages: dormancy induction and stress conditioning.
13

actively growing and have little cold hardiness. Because 

these "hot planted" seedlings are shipped while still relatively 

succulent, they cannot be cold-stored and must be 

outplanted within a few days.

Fall outplanting--This stock receives a moderate amount of 

hardening, but seedlings are not fully dormant when shipped. 

Although stem tissue has lignified, seedlings are not fully cold 

hardy. Buds will have formed in determinant species. This 

degree of hardening takes 3 to 5 weeks to achieve, but root 

systems are still active.

Winter or spring outplanting--These outplantings require fully 

hardened seedlings with well-developed, dormant shoots and 

stock is typically cold stored for at least a few weeks. Because of 

their high level of cold hardiness, these seedlings have 

maximum resistance to all types of stresses. Full hardiness 

typically requires 6 to 10 weeks to complete. (The hardening 

phase is discussed in detail in chapter 4 of this volume.)

Dormancy induction. Because seedling growth cannot be stopped 

abruptly, the hardening phase must be initiated when seedlings are 

approximately 80 to 90% of the actual target to account for this 

"growth coast." While shoot growth begins to slow down, stem 

diameter continues to increase toward its target (figure 6.1.9). In 

most species that exhibit determinate growth, bud development 

starts during this stage. With indeterminate species such as 

southern pines and junipers, a true bud does not form and the 

shoot simply stops growing.

Stress conditioning. Container seedlings are extremely succulent 

after the rapid growth phase and have little stress tolerance. 

Therefore, they must be gradually hardened to tolerate the many 

stresses of harvesting, handling, storage, and outplanting. Timing 

and duration of the hardening phase will depend on when 

seedlings will be outplanted, and the types of stresses that will be 

encountered on the outplanting site:

• Summer outplanting-Seedlings that will be outplanted during summer on relatively low-stress sites are still
6.1.3 Constructing a Propagation Protocol

A propagation protocol is a comprehensive and systematic 

documentation of all the steps necessary to propagate a plant, 

starting with collection of seeds or cuttings and ending with harvest, 

storage and shipping. A typical propagation protocol for bur oak is 

shown in table 6.1.2.

6.1.3.1 Sources of propagation information

Compared to ornamental crops, forest and conservation species 

pose a difficult problem because of the sheer number of species 

and ecotypes, some of which are not widely propagated, if at all. In 

addition, specific growing schedules are not normally published 

because they vary so much with individual species response and 

nursery climate. There are, however, sources of information for 

constructing a propagation protocol (Munson and Nicholson 1994):

Systematically search the published literature. It is possible that 

someone has propagated the species before, so the first step is to 

conduct a literature search. General horticultural texts may contain 

some specific information but you will have more luck with technical 

journals and nursery trade magazines. For example, the article 

"Propagation of Fraser Fir" in the Journal of Environmental 

Horticulture provides a comprehensive picture of how to propagate 

this species by seed or vegetatively (Blazich and Hinesley 1994). In 

particular, the Combined Proceedings of the International Plant 

Propagators’ Society is a wealth of information. Regional and 

special publications from botanic gardens and native plant societies 

can also be helpful. A list of general propagation references is 

provided in section 6.1.5.2 of this volume.

Compare propagation methods for related species. If specific 

information for the species is unavailable, information on how close 

relatives within the genus or even family are propagated may be 

useful. These relatives must grow in the general climatic zone. 

However, it should be remembered that there can be considerable 

variation even within a genus. For example, seed stratifi cation 

requirements for maple species can vary considerably (Schopmeyer 

1974).

Study the native environment and natural growth habit of the 

plant. Environmental factors such as total precipitation, its season 

of distribution, and maximum/minimum temperatures may affect 

seed germination. Most forest and conservation species from the 

Temperature Zone require some exposure to cold temperatures 

and

14

moist conditions that naturally occur during winter. Species from 

this climate, therefore, would logically require a cold-moist 

stratification treatment before seeds will germinate. Species 

adapted to fire-dominated ecosystems, such as many of the 

chaparral species, have seeds that require treatment with hot 

water or even smoke. Species that grow in low thickets, such as 

rose and wild berries, root quite easily and so can be vegeta tively 

propagated by cuttings or layering.

Many other clues can be gained by studying how plants grow in 

nature. When constructing a seed propagation protocol, ecological 

information such as its growth habit and type of fruit may provide 

helpful clues (Finnerty 1994). In particular, information on how 

seeds are disseminated in nature and which relative habitat a 

species occupies in nature can be helpful (table 6.1.3). However, 

growers must be alert for misinformation. For example, it is 

commonly believed that Indian paintbrush cannot be propagated 

because it is often found living as a semiparasite on sagebrush and 

other plants. Inspection of the seedcoat reveals one of the 

problems-it contains a network of fine hairs that inhibit water 

absorption. This impediment can be easily removed by hand 

rubbing (Borland 1996).

Consult with other nurseries growing the same or similar 

species. New nursery managers, in particular, are going to need 

some basic cultural information before starting to plan for a potential 

crop. The indirect experience gained by talking to other growers, 

although time-consuming, is valuable. Many private nurseries do 

not want to share their propagation secrets for obvious reasons, but 

government nurseries are excellent sources of technical 

information, as most consider technology transfer to be part of their 

mandate. There are native plant societies in almost every state or 

often the horticulturist at regional botanical gardens would be happy 

to share information. The Denver Botanical Garden has propagated 

1,000 to 2,000 species of native plants (Borland 1996).

There are a few technical publications, such as the USDA Forest 

Service's classic Seeds of Woody Plants in the United States 

(Schopmeyer 1974), that provide general information on seed 

collection, processing, storage, and nursery culture. [A newer 

version of this valuable book has been republished by Young and 

Young (1992), who included additional species. The Forest Service 

is working at this time to revise Seeds of Woody Plants..., and plans 

to publish it again as the Woody Plant Seed
15
Manual (its popular name) and make it available on the World 

Wide Web.] The Forest Research Nursery at the University of 

Idaho has published a series of technical bulletins that describe 

cultural techniques and growing regimes that they have 

developed for most commercial conifers in their region (Wenny 

and Dumroese 1987a,b,c; 1988; 1990a,b; 1991; 1992). Many 

government nurseries have operating manuals that are also an 

excellent source of cultural information. Most of these

16

have never been formally published, but they may be willing to 

make copies. For example, information on propagating diverse 

species is particularly difficult to find but the Greenhouse and 

Shadehouse Production Manual from the Mason State Nursery in 

Illinois covers grasses, forbs, wildflowers, riparian and wetland 

plants, woody shrubs, and trees for the Great Plains (Mountz 

1993). (A list of other publications containing specific propagation 

information can be found in section 6.1.6.1.)
produce a seedling crop, and so crop production schedules are 

particularly useful for explaining all the various steps in the nursery 

process and the time involved. For example, a crop production 

schedule will illustrate that it will be necessary to ship seeds to the 

nursery several months prior to sowing, especially if germination 

tests and presowing seed treatments are necessary. These growing 

schedules are also useful in illustrating how different seedling 

stocktypes are produced, the time required to grow them, and when 

they would be available for outplanting (table 6.1.4).

Crop production schedules mu st reflect the biological 

requirements of the species that will be grown, and take greatest 

advantage of available sunlight.

Cultural groups. Another important consideration when planning 

growing schedules is the concept of cultural groups. Although all 

plant species respond differently to nursery culture, nursery 

managers should analyze characteristics of the plants that they will 

be growing and group them by similar responses. Even species that 

grow together in the same natural environment often perform very 

differently when sown together in the nursery. For example, western 

white pine and western larch, although found in the same forests of 

northern Idaho, have radically different responses to nursery 

culture, especially nitrogen (N) fertilization (Eggleston 1994). 

Western larch is a fast-growing species that requires fertilizer 

containing as little as 50 ppm N, whereas western white pine grows 

much slower and so must be given fertilizer with over 200 ppm of N. 

Therefore, western larch should be placed in one cultural group with 

other nitrogen-sensitive trees (such as quaking aspen) and western 

white pine should be placed in another, slower-growing cultural 

group.

Solar timing. Because of seasonal changes in the Temperate 

Zone, forest and conservation nursery crops are scheduled around 

the solar cycle (figure 6.1 .11). Both light intensity and daylength 

vary considerably during the year, so nursery managers must plan 

their crops around the summer solstice to take full advantage of 

available sunlight. For crops grown in propagation structures, 

summer crops are cheaper to produce because less heat is 

required (Clements and Dominy 1990). This is particularly critical 

when multiple cropping because the first crop must be grown before 

the solstice so that the second crop can be sown early enough to 

grow to full size during the remainder of the growing season. For 

example, the spring crop would be sown in early February in a 

propagation structure and then removed to

17

6.1.3.2 Growing schedules

Growing schedules are an essential part of a propagation protocol 

because they provide a good way to visually illustrate the steps in 

the protocol and how they relate in time. They serve as visual time 

charts of the type of propagation environment that must be 

maintained and cultural operations and processes that are needed 

from seed preparation to seedling shipment. If detailed economic 

data are also recorded, growing schedules can be used to illustrate 

costs and benefits of different growing regimes (Clements and 

Dominy 1990).

We recommend three different types of growing schedules: crop 

production, facilities, and cultural. Within each, the format is 

basically the same-time is plotted along the top of the chart with 

cultural and management factors along the right side. Time 

intervals will vary from weeks to months to years, depending on 

which factors are being tracked and the amount of detail that is 

needed. All growing schedules are filled-out in the same way. Start 

with the date that the crop must be shipped and work backwards, 

blocking out sections of time for the various operations until you 

reach the date at which the crop must be started. Although 

schedules will vary from nursery to nursery, the important point is 

not the format itself but rather that nursery managers have a 

detailed plan of action before starting the crop.

Although they can be drafted by hand, growing schedules are easy 

to construct with modern word processing or spreadsheet computer 

software programs. The sample schedules shown in tables 6.1.4, 

6.1.5, and 6.1.6 were all developed in WordPerfect 8.0© in a couple 

of hours using the "Table QuickCreate" feature. Once the overall 

framework of the growing schedule is complete, then various 

features can be easily typed into cells. Features like background 

shading and special fill designs make the information even easier to 

understand. Blank forms of the growing schedules used in this 

section are provided in the appendix of this chapter; contact the 

senior author for copies of the computer files.

Crop production schedules. The first and most long-term type of 

growing schedule is the crop production schedule, which is 

designed to help the manager visualize "the big picture". These 

schedules typically are designed on a month-by-month time scale, 

cover at least 1 year, and include all phases of nursery production 

from crop planning to outplanting (table 6.1 .4). Many nursery 

customers fail to appreciate how long it really takes to
a shadehouse or open growing area in early June to finish the 

hardening phase. The fall crop would be sown at this time and then 

left to harden in the propagation structure (figure 6.1 .11). Because 

air and soil temperatures lag considerably behind the solar cycle, 

multiple crops must be carefully scheduled so that they take 

advantage of solar light but are not damaged by late spring frosts. 

(More details on solar light cycles can be found in volume three of 

this series.)

Facilities schedules. The second type of growing schedule is the 

facilities schedule, which illustrates the space requirement that 

each crop will require in the various propagation environments, 

processing and storage facilities. This schedule also lists labor, 

equipment, and supplies needed to produce the crop. Nursery 

facilities schedules are organized by months and often cover 2 

years (table 6.1 .5).

18
As an example, consider the facilities schedule for two different 

conifer seedling crops at a container nursery in northern Idaho. The 

first crop is western white pine, to be grown in a double-poly 

greenhouse for fall outplanting (table 6.1.5A). Note that seeds must 

be received at the nursery by September of the year before sowing 

because this species requires a relatively long (120-day) cold-moist 

stratification treatment. The crop will be sown in mid-January to 

allow enough time for the seedlings to meet target specifications by 

the shipping date. Experience with past crops has shown that this 

earlier sowing is necessary for this relatively slow-growing species 

(Eggleston 1994). This schedule shows that workers will be needed 

during late fall to clean used containers in the headhouse and to 

sterilize the greenhouse before sowing. The sowing line must be 

assembled during early January and then crews will be needed 

again in late February for thinning. The final labor requirement for

this crop will be in mid-June, when the packing line will need to be 

assembled so that seedlings can be graded, packed, and shipped 

during the outplanting window (table 6.1 .5A).

Continuing with this example, the second crop is high-elevation 

Douglas-fir (table 6.1 .513). This species must be outplanted during 

the fall because the sites do not become clear of snow until too late 

in the spring. Douglas-fir seeds require only 6 weeks of cold-moist 

stratifi cation before sowing in mid-February, and high elevation 

ecotypes of this species are particularly slow-growing. Therefore, 

this second crop will be grown for 5 months in a double-poly 

greenhouse and then moved to a shelterhouse for hardening.

This two-crop example shows how facilities schedules help to 

coordinate work crews and equipment (see

19
"Labor needs" in tables 6.1.5A/B). One work crew can be used to 

clean containers and prepare the propagation structures for both 

crops. Because of staggered sowing dates, the sowing line has to 

be assembled only once and the same work crew can be used to 

sow both crops. This crew can then stay on to do the thinning as 

the seedlings emerge. The crew that returns in mid-June to harvest 

the white pine crop will stay over to move the Douglas-fir seedlings 

to the shelterhouse.

Cultural schedules. Cultural schedules are the most detailed of the 

growing schedules used in forest and conservation nurseries (tables 

6.1 .6A/B). They are valuable not only for reference while the crop is 

growing but also can be filed to document the actual time and 

environmental conditions that were used to produce the crop. These 

"planned" and "actual" records can then be consulted to modify 

cultural schedules for subsequent crops. This is particularly easy 

when the schedules are con20

structed as computer documents that can be easily modified and 

stored.

Even though cultural schedules may differ slightly in format, there 

are common factors that should be included: the month and week, 

the number of weeks from sowing, the propagation environment, 

target seedling specifications, and the growth stage at that particular 

time in the crop cycle (tables 6.1.6A/B). The schedules also should 

contain room to list specific cultural processes and operations, such 

as thinning or seedling inventory. The size of work crew for that 

particular process also could be recorded. Each of the potential 

growth-limiting environmental factors should be listed along the left 

margin of the schedule form along with any pertinent information 

about how they will be controlled and monitored. Some 

environmental factors will be listed as discrete numbers whereas 

others should be listed as ranges. In fully controlled or 

semi-controlled propagation structures, temper-
21
22
hardwood cuttings, need a period of cold-moist stratification. (See 

chapters 2 and 3 in this volume for further discussion on these 

treatments.)

6.1.3.4 Scheduling seedling growth phases

The establishment, rapid growth, and hardening phases are easily 

incorporated into growing schedules. Facilities schedules provide 

an overview of how growth phases fit into the total crop cycle 

(tables 6.1.5A/B) and are useful for general planning purposes. The 

more short-term cultural schedules are useful in showing the really 

critical times in the crop cycle when environmental conditions must 

be changed radically. When posted in the headhouse, cultural 

schedules provide an easy way to alert the grower and the rest of 

the nursery crew. For example, the change from the germination 

stage to the early growth stage requires a reduction in temperature 

and relative humidity (table 6.1 .6A). At the same time, the 

photoperiod lights and the carbon dioxide generators are turned on. 

The crew must also be alerted to change from a frequent mist to a 

periodic irrigation that is controlled by block weight, and start 

"fertigation" (injecting liquid fertilizer into irrigation water, that is, 

fertilization + irrigation). Proper implementation and coordination of 

these various changes is made easier with a comprehensive 

cultural schedule that can be frequently consulted in case of 

confusion about specific instructions.

Likewise, when the propagation environment must be changed to 

start the hardening phase at week 20, a well-designed cultural 

schedule fully illustrates the entire process (table 6.1.6B). For 

species such as white spruce that exhibit free shoot growth, bud 

development must be induced by a radical change in the 

propagation environment to subject the seedlings to a physiological 

"shock." Four environmental factors are key in triggering hardening: 

temperature, daylength, water, and mineral nutrients, especially 

nitrogen. In this example, both day and night temperatures are 

reduced substantially, photoperiod lights are turned off, and 

seedlings are brought into a mild water and nutrient stress. The 

growing medium is allowed to dry and the nitrogen level also is 

reduced (table 6.1.6B). Again, the crop schedule serves to alert the 

nursery crew to the change in propagation environment and 

provides the specific details for easy reference. (Much more 

detailed information on the hardening phase is provided in chapter 4 

of this volume.)

23

atures for both day and night could be specified as discrete set 

points that correspond to the setting on the thermostat or 

environmental control computer. In open growing compounds, 

growers would list the ideal temperature for that growth stage and 

then record the actual ambient temperature. Because it is more 

difficult to control precisely and is not as critical to seedling growth, 

relative humidity could either be listed as a set point or an allowable 

range, for example, "60-80% during the establishment phase" 

(tables 6.1 .6A/B). Other cultural information is recorded according 

to the nature of the environmental factor and the ability to control it. 

For example, if carbon dioxide generators are used in fully 

controlled propagation structures, a target of 1,000 parts per million 

(ppm) might be listed. In semi- controlled structures or open growing 

compounds, ambient would be recorded in the cultural schedule. 

The same procedure is done for irrigation, fertilization, and other 

cultural factors. Nursery pests, which can sometimes be limiting to 

seedling growth, should also be recorded in the cultural schedule 

along with plans for monitoring and control.

The accumulated information recorded in cultural schedules is 

valuable for monitoring seedling growth patterns as well as 

identifying the need for different environmental control equipment or 

different types of propagation structures.

6.1.3.3 Collection and preparation of propagules

One of the most common mistakes made by novice nursery 

managers during crop planning is not allowing enough time to 

collect and prepare the seeds, cuttings, or other propagation 

material. Sometimes these are provided by the customer, but other 

times seeds must be purchased from a commercial source or the 

cuttings collected by the grower. Although seeds of most 

commercial forest species are sold by seed dealers, it may be 

difficult to find the proper seed source for a planting project on short 

notice. (See section 6.2.2 in this volume for more information on 

purchasing seed.)

The processing of seeds or cuttings also takes time. Seeds of many 

forest and conservation species do not germinate readily when 

freshly collected or taken directly out of storage, and require a 

period of water soaking, cold-moist stratification, or other 

time-consuming presowing treatment (tables 6.1.5A/B). Some types 

of cuttings can be collected and used immediately, but others, 

especially
24

6.1.3.5 Testing and adjusting protocols

It must be emphasized that propagation protocols are only a guide 

and that the crop will rarely perform exactly as projected. Because 

of year-to-year variations in weather conditions and unforeseen 

cultural or operational problems, it will be necessary to continually 

fine-tune protocols. Therefore, growers must monitor seedling 

growth and environmental conditions in the propagation 

environment, and record any discrepancies between expected and 

observed performance. As soon as seedling growth rate or 

development begins to deviate significantly from projected growth 

schedules, then specific changes will have to be made in the level of 

one or more of the environmental factors. For example, if the 

seedling growth rate of a species begins to lag behind the projected 

shoot height curve, then the nitrogen fertilizer level could be 

increased to try to accelerate shoot growth (figure 6.1.12).

Any changes must be carefully noted in crop records and growing 

schedules adjusted accordingly. If possible, the nursery manager 

should try to analyze the exact cause for the needed adjustment so 

that growing schedules for future crops will be even more accurate.
6.1.4 Summary

Crop planning is a critical but often overlooked part of plant 

propagation. The planning process must consider the biology of 

the species, desired genetic variation, availability of propagules, 

and the objectives of the outplanting project. Using this 

information, the grower decides whether seed or vegetative 

propagation would be most appropriate.

Crop scheduling can be divided into three seedling growth phases: 

establishment, rapid growth, and hardening with the cultural specifics outlined in a propagation protocol. 

Growing schedules provide a good way to visually illustrate the 

steps in the protocol and how they relate in time. Cultural 

information can either be gained directly through experience, from 

published articles, or from tips from other growers. Regardless of 

the source, propagation protocols must be tested in the specific 

nursery environment and need to be continually updated as more 

cultural knowledge is acquired.

25
6.1.5 References

6.1.5.1 Literature cited

BC Ministry of Forests. 1998. Provincial seedling stock type 

selection and ordering guidelines. Victoria, BC: British 

Columbia Ministry of Forests, Silviculture Branch. 71 p.

Blazich FA, Hinesley LE. 1994. Propagation of fraser fir. Journal of 

Environmental Horticulture 12(2): 112-117.

Borland J. 1996. Changing your propagation paradigms. American 

Nurseryman 183(5): 24-29.

Bowden R, Scagel RG. 1994. Long-term stock type trial results in 

B.C.: did stock performance meet today's standards? In: Landis 

TD, Dumroese RK, tech. coords. National Proceedings, Forest 

and Conservation Nursery Associations. Gen. Tech. Rep. 

RM-257. Fort Collins, CO: USDA Forest Service, Rocky 

Mountain Forest and Range Experiment Station: 93-98.

Clements SE, Dominy SWJ. 1990. Costs of growing containerized 

seedlings using different schedules at Kingsclear, New 

Brunswick. Northern Journal of Applied Forestry 7(2): 73-76.

Eggleston K. 1994. Personal communication. Coeur d' Alene, 

ID: USDA Forest Service, Coeur d' Alene Nursery.

Finnerty TL. 1994. Native woody shrub propagationthree key 

steps, part 1 : know your plants. Plant Propagator 6(1): 

16-17.

Hartmann HT, Kester DE, Davies FT Jr, Geneve RL. 1997. Plant 

propagation: principles and practices. 6th ed. Englewood Cliffs, 

NJ: Prentice Hall. 770 p.

Johnson F, Paterson J, Leeder G, Mansfield C, Pinto F, Watson 

S. 1996. Artificial regenerations of Ontario's forests: species 

and stock selection manual. For. Res. Info. Pap. 131. Sault 

Ste. Marie, ON: Ontario Forest Research Institu te. 52 p.

Kozlowski TT. 1971. Growth and development of trees. Volume 

1, Seed germination, ontogeny, and shoot growth. New York: 

Academic Press. 443 p.

MacDonald J. 1998. Personal communication. 

Fredericton, NB: Canadian Forest Service.

McGilvray JM, Barnett JP. 1982. Relating seedling morphology to 

field performance of containerized southern pines. In: Guldin 

RW, Barnett JP., eds., Proceedings, Southern Containerized 

Tree Seedling Conference. Gen. Tech. Rep. SO-37, New 

Orleans: USDA Forest Service Southern Forest Experiment 

Station: 39-46.

Mountz RD. 1993. Greenhouse and shadehouse production 

manual. Mason, IL: Illinois Department of Conservation, Mason 

State Nursery. 34 p.

26

Munson RH, Nicholson RG. 1994. A germination proto col for small 

seed lots. Journal of Environmental Horticulture 12(4): 

223-226.

Powell GR. 1982. A comparison of early shoot development of 

seedlings of some trees commonly raised in the Northeast of 

North America. In: Proceedings, Northeastern Area 

Nurserymen's Conference; 1982 July 25-29; Halifax, NS. 

Truro: Nova Scotia Department of Lands and Forests: 1-24.

Rose R, Carlson WC, Morgan P. 1990. The target seedling 

concept. In: Rose, R.; Campbell SJ, Landis TD, eds. Target 

Seedling Symposium: Proceedings, Combined Meeting of the 

Western Forest Nursery Associations; 1990 August 13-17; 

Roseburg, OR. Gen. Tech. Rep. RM-200. Ft. Collins, CO: USDA 

Forest Service, Rocky Mountain Forest and Range Experiment 

Station: 1-8.

Schopmeyer CS, tech. coord. 1974. Seeds of woody plants in 

the United States. Agric. Handbk. 450. Washington, DC: 

USDA Forest Service. 883 p.

Thompson S. 1989. Environmental control of shoot growth in 

Scots pine, Sitka spruce and Douglas-fir seedlings. 

Forestry (Supplement) 62: 182-188.

van Steenis E. 1993. Targeting specific crop rearing procedures, 

forest seedling grower course. Surrey: British Columbia 

Ministry of Forests, Nursery Extension Services. 10 p.

Von Wuehlisch G, Muhs HJ. 1991. Environmental influences on 

juvenile shoot growth in Picea abies. Scandinavian Journal of 

Forest Research 6: 479-498.

Wenny DL, Dumroese RK. 1987a. A growing regime for 

containerized western larch seedlings. Bull. 42. Moscow, ID: 

University of Idaho, College of Forestry, Wildlife and Range 

Sciences. 8 p.

Wenny DL, Dumroese RK. 1987b. A growing regime for 

containerized ponderosa pine seedlings. Bull. 43. Moscow, ID: 

University of Idaho, College of Forestry, Wildlife and Range 

Sciences. 9 p.

Wenny DL, Dumroese RK. 1987c. A growing regime for 

containerized western white pine seedlings. Bull. 44. Moscow, 

ID: University of Idaho, College of Forestry, Wildlife and Range 

Sciences. 9 p.

Wenny DL, Dumroese RK. 1988. A growing regime for 

containerized grand fir seedlings. Bull. 45. Moscow, ID: 

University of Idaho, College of Forestry, Wildlife and Range 

Sciences. 8 p.

Wenny DL, Dumroese RK. 1990a. A growing regime for 

containerized western redcedar seedlings. Bull. 46. Moscow, 

ID: University of Idaho, College of Forestry, Wildlife and Range 

Sciences. 8 p.
27

Landis TD, tech. coord. 1993. Proceedings, Western Forest 

Nursery Association; 1992 September 14-19; Fallen Leaf 

Lake, CA. Gen. Tech. Rep. RM-221. Ft. Collins, CO: USDA 

Forest Service, Rocky Mountain Forest and Range 

Experiment Station. 151 p.

Link E, ed. 1993. Native plant propagation techniques for national 

parks: interim guide. East Lansing, MI: Rose Lake Plant 

Materials Center. 240 p.

Macdonald B. 1986. Practical woody plant propagation for 

nursery growers. Volume 1 . Portland, OR: Timber Press. 669 

p.

Murphy P, comp. 1984. The challenge of producing native plants 

for the Intermountain area; Proceedings, Intermountain 

Nurseryman's Association 1983 conference; 1983 August 8-11; 

Las Vegas, NV. Gen. Tech. Rep. INT-168. Ogden, UT: USDA 

Forest Service, Intermountain Forest and Range Experiment 

Station. 96 p.

Redente EF, Ogle PR, Hargis NE. 1982. Growing Colorado 

plants from seed: a state of the art. Volume 3, Forbs. Pub. 

FWS/OBS-82/30. Washington, DC: USDI Office of Biological 

Services, Fish and Wildlife Service. 113 p.

Rose R, Chachulski CEC, Haase DL. 1998. Propagation of 

Pacific Northwest native plants. Corvallis: Oregon State 

University Press. 248 p.

Tinus RW, McDonald SE. 1979. How to grow tree seedlings in 

containers. Gen. Tech. Rep. RM-60. Fort Collins, CO: USDA 

Forest Service, Rocky Mountain Forest and Range 

Experiment Station. 256 p.

Vories KC. 1981. Growing Colorado plants from seed: a state of 

the art. Volume 1, Shrubs. General Tech. Rep. INT-103. 

Ogden, UT: USDA Forest Service, Intermountain Forest and 

Range Experiment Station. 80 p.

Wenny DL, Dumroese RK. 1990b. A growing regime for 

container-grown spruce seedlings. Bull. 47. Moscow, ID: 

University of Idaho, College of Forestry, Wildlife and Range 

Sciences. 8 p.

Wenny DL, Dumroese RK. 1991. A growing regime for 

container-grown Scotch and Austrian pine seedlings. Bull. 48. 

Moscow, ID: University of Idaho, College of Forestry, Wildlife 

and Range Sciences. 8 p.

Wenny DL, Dumroese RK. 1992. A growing regime for 

container-grown Douglas-fir seedlings. Bull. 49. Moscow, ID: 

University of Idaho, College of Forestry, Wildlife and Range 

Sciences. 8 p.

Wood B. 1994. Conifer seedling grower guide. Smoky Lake, AB: 

Pine Ridge Forest Nursery. 73 p.

Young E, Hanover JW. 1978. Effects of temperature, nutrient, 

and moisture stresses on dormancy of blue spruce seedlings 

under continuous light. Forest Science 24(4): 458-467.

Young JA, Young CG. 1992. Seeds of woody plants in North 

America. Portland, OR: Dioscorides Press. 407 p.

6.1.5.2 General propagation references

Belcher E. 1985. Handbook on seeds of browse-shrubs and 

forbs. Tech. Pub. R8-TP8. Atlanta: USDA Forest Service, 

Southern Region. 246 p.

Dirr MA, Heuser CW Jr. 1987. The reference manual of woody 

plant propagation: from seed to tissue culture. Athens, GA: 

Varsity Press. 239 p.

Emery DE. 1988. Seed propagation of native California plants. 

Santa Barbara, CA: Santa Barbara Botanic Garden. 115.

Fulbright TE, Redente EF, Hargis NE. 1982. Growing Colorado 

plants from seed: a state of the art. Volume 2, Grasses and 

grasslike plants. Pub. FWS/OBS-82/29. Washington, DC: USDI 

Office of Biological Services, Fish and Wildlife Service. 113 p.
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