Pinus ponderosa: 

A Taxonomic Review 

With Five Subspecies 

in the United States

Robert Z. Callaham

Pacific Southwest 

Research Station

Research Paper 

PSW-RP-264

September 2013

DEPAR TMENT OF AGRICULT URE

United States Department of Agriculture

Forest Service
Author

Robert Z. Callaham (retired) was a botanist and geneticist with the Pacific 

Southwest Research Station, 800 Buchanan Street, West Annex Building, Albany, 

CA 94710-0011. He served as station director from 1976 to 1983 and as de facto 

director of the Wildland Resources Center, University of California, from 1983 to 

1990. He can be reached at rzcallaham@comcast.net.

Cover photograph: Ponderosa pine stand; photo copyright by Miles Hemstrom.

The U.S. Department of Agriculture (USDA) prohibits discrimination against its 

customers, employees, and applicants for employment on the bases of race, color, 

national origin, age, disability, sex, gender identity, religion, reprisal, and where 

applicable, political beliefs, marital status, familial or parental status, sexual orientation, 

or all or part of an individual’s income is derived from any public assistance program, 

or protected genetic information in employment or in any program or activity conducted 

or funded by the Department. (Not all prohibited bases will apply to all programs and/or 

employment activities.) 

If you wish to file an employment complaint, you must contact your agency’s EEO 

Counselor (PDF) within 45 days of the date of the alleged discriminatory act, event, or 

in the case of a personnel action. Additional information can be found online at http://

www.ascr.usda.gov/complaint_filing_file.html. 

If you wish to file a Civil Rights program complaint of discrimination, complete the USDA

Program Discrimination Complaint Form (PDF), found online at http://www.ascr.usda.

gov/complaint_filing_cust.html, or at any USDA office, or call (866) 632-9992 to request 

the form. You may also write a letter containing all of the information requested in the 

form. Send your completed complaint form or letter to us by mail at U.S. Department 

of Agriculture, Director, Office of Adjudication, 1400 Independence Avenue, S.W., 

Washington, D.C. 20250-9410, by fax (202) 690-7442 or email at program.intake@

usda.gov. 

Individuals who are deaf, hard of hearing or have speech disabilities and you wish to file 

either an EEO or program complaint please contact USDA through the Federal Relay 

Service at (800) 877-8339 or (800) 845-6136 (in Spanish). 

Persons with disabilities who wish to file a program complaint, please see information 

above on how to contact us by mail directly or by email. If you require alternative means 

of communication for program information (e.g., Braille, large print, audiotape, etc.) 

please contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD). 

For any other information dealing with Supplemental Nutrition Assistance Program 

(SNAP) issues, persons should either contact the USDA SNAP Hotline Number at (800) 

221-5689, which is also in Spanish or call the State Information/Hotline Numbers. 

For any other information not pertaining to civil rights, please refer to the listing of the 

USDA Agencies and Offices for specific agency information.
Abstract

Callaham, Robert Z. 2013. Pinus ponderosa: a taxonomic review with five subspecies in the United States. Res. Pap. PSW-RP-264. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 52 p.

Various forms of Pinus ponderosa Douglas ex C. Lawson are found from British 

Columbia southward and eastward through 16 states and, perhaps, into Mexico. 

The status of many names previously associated with this species, but excluded 

here, has been clarified. Accumulated evidence based on variation in morphology and xylem monoterpenes, partial genetic barriers to crossing, and allozyme 

differences leads to recognition of five subspecies:

1. Pinus ponderosa subsp. ponderosa, Columbia ponderosa pine, southward from southern British Columbia, east of the Cascade Range in 

Washington, Oregon, and northeastern California and eastward to the 

Continental Divide.

2. Pinus ponderosa subsp. critchfieldiana Callaham, subsp. nov., Pacific 

ponderosa pine, from Puget Sound, Washington, southward to southern 

California.

3. Pinus ponderosa subsp. scopulorum (Engelm. in S. Watson) E. Murray, 

Rocky Mountains ponderosa pine, from the Continental Divide in 

Montana eastward to the Black Hills of South Dakota and southward into 

Utah and Colorado.

4. Pinus ponderosa subsp. readiana Callaham, subsp. nov., central high 

plains ponderosa pine, restricted to Nebraska and adjacent areas in South 

Dakota, Wyoming, and Colorado.

5. Pinus ponderosa subsp. brachyptera (Engelm. in Wislizenus) 

Callaham, comb. nov., southwestern ponderosa pine, in Arizona, New 

Mexico, Oklahoma, and southwestern Texas, and, probably, extending 

into Mexico. 

Transition zones occur between subspecies.

Keywords: Ponderosa pine, Pinus ponderosa, taxonomy, subspecies.

1

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Introduction

Ponderosa pine, Pinus ponderosa Douglas ex C. Lawson, is a widespread species 

that differs substantially in morphology across its range, with resultant confusion 

in its taxonomy. It grows in various forms over a large area extending from British 

Columbia southward and eastward through 16 states.1

During the 1800s, separate botanical discoveries of the species in Montana, 

Wyoming, Colorado, Washington, California, and New Mexico resulted in it being 

called by different names. This confusion was compounded during the latter part 

of the 19th century when taxonomists included closely related species as varieties of 

ponderosa pine. Discoveries and taxonomy of ponderosa pine are reviewed here. A 

comprehensive description of the species is provided.

Since the early 1900s, ponderosa pine has been regarded as composed of two 

(or three) varieties or subspecies. Forestry scientists have exerted much effort to 

understand and utilize this genetic variability. Their studies have identified and 

characterized numerous geographic races and transitional zones. Five of these races 

are described here as subspecies (fig. 1).

Literature Review

Copies of relevant pages from historical botanical writings cited in this manuscript 

are in research files at the Institute of Forest Genetics, Placerville, California.

Taxonomic History

According to Sargent (1897):

The first published allusion to Pinus ponderosa is in the journal of Lewis 

and Clark, who, in ascending the Missouri River in September, 1804, at 

the outset of their transcontinental journey, found the cones of this tree, 

brought down from the pineries of northwestern Nebraska, floating on 

White River, and heard of the pine forest on the Black Hills of Dakota.

Lewis and Clark’s journal entry (Coues 1893, p. 117 and 150) is more ambiguous:

September 15th. (1804) We passed, at an early hour, the creek near last 

night’s camp; and at two mile’ distance reached the mouth of White river, 

coming in from the south. ... the sergeant (Gass), who ascended about 

twelve miles; ... he saw pine burrs [sic—pine cones], and sticks of birch 

were seen floating down the river; ...

October 2d. (1804) ... The Black mountains (Hills), he (Mr. Valle, a French 

trader) observes, are very high, covered with great quantities of pine, ...

1 Ponderosa pine may extend into Mexico despite the contrary contention of Perry (1991).
2

RESEARCH PAPER PSW-RP-264

Figure 1—Location of subspecies and transition zones of ponderosa pine north of Mexico. Base map adapted from Little (1971).
3

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Later, Lewis and Clark (Coues 1893, p. 305), when at a point now on the north 

shore of Fort Peck Lake, Montana, currently called “Pines Campground” and 

managed by the U.S. Army Corps of Engineers, wrote the first description of Rocky 

Mountains ponderosa pine:

May 11th. (1805) ... We saw and visited some high hills on the north side 

about three miles from the river, whose tops were covered with the pitchpine. This is the first pine we have seen on the Missouri; it is like that of 

Virginia [Pinus rigida Mill.], except that the leaves are somewhat longer.

Lewis and Clark (Coues 1893, p. 318) referred again to ponderosa pine when 

they first viewed the large stand extending along both banks of the Missouri River 

at the southern boundaries of Phillips and Blaine Counties, Montana:

May 21st. (1805). ... In its course the Missouri makes a sudden and extensive bend toward the south, to receive the waters of the Muscleshell. ... The 

country on the south is high, broken, and crowned with some pine and 

dwarf cedar; the leaf of this pine is longer than that of the common pitch 

or red pine of Virginia [Pinus rigida]; the cone is longer and narrower, the 

imbrications are wider and thicker, and the whole is frequently covered 

with rosin.

Lauria (1996) wrote: 

Pinus ponderosa s.l. is a commercially important and polymorphic conifer. 

Its taxonomy (and that of its entire group, the “ponderosa complex”) is far 

from being settled. This unsettled status is largely due to absence of a type, 

a circumstance that also accounts for the fact that even the very identity of 

Pinus ponderosa s.str. itself is notoriously confused. The earliest sources 

documenting the intricacies of the discovery and late publication of ponderosa pine as a new species in 1836 were reviewed. Detailed study of its 

earliest botanical history is demonstrated to be essential to finally establish 

its original identity, as meant by David Douglas and described by Charles 

Lawson. Pinus ponderosa Douglas ex C. Lawson is then neotypified with 

authentic material (an ovuliferous cone) discovered in a historical collection 

of conifer cones surviving at the Natural History Museum in Vienna, Austria (W). The extensive synonymy pertaining to the “ponderosa complex” 

is reviewed (including typification of several of these synonyms) and some 

new facets of the life and achievements of David Douglas, who is commonly credited with the discovery of Pinus ponderosa, are also reported 

here for the first time.
4

RESEARCH PAPER PSW-RP-264

Further, according to Lauria:2 foliage specimens of Pinus ponderosa collected 

by Lewis and Clark were mounted (in about 1810) by Frederick Pursh, were rediscovered in 1897 by Thomas Meehan, and are:

“...in the custody of the Academy of Natural Sciences in Philadelphia.”

Lewis’ original annotations on the specimens, having in most cases been 

made on paper of poor quality, are not preserved. But Pursh as a rule transcribed Lewis’ annotations correctly, although not necessarily verbatim. 

On both of the sheets of Lewis’ ponderosa pine preserved today, the labels 

deviate only little in content:

On the Kooskooskee / On River bottoms, in / rich land, west of the / 

mountains. / Octbr. 1st 1805. The specimens only consist of sterile parts; 

reproductive parts are neither present today nor is their former existence 

documented anywhere.

Because the material was destitute of cones, and because Lewis used the 

name “long-leafed pine” on several occasions in his journal, what other 

choice would any herbarium taxonomist (like Pursh in 1814!) have but to 

identify this material as P. palustris?—the collection by Lewis and Clark 

had been identified erroneously as Pinus palustris L. by F. Pursh.

Lauria commented further: “The chronologically next allusion to P. ponderosa

is that of Edwin James (1823, 1825) who erroneously identified it as Pinus resinosa

(without author!) in 1820.”

Edwin P. James (1825), Assistant Surgeon, U.S. Army, described and catalogued plants collected during the expedition to the Rocky Mountains commanded 

by Major Stephen H. Long. James was taken on the expedition specifically to serve 

as botanist and geologist. James erroneously identified, as Pinus resinosa, ponderosa pines that he encountered on Platte River, Wyoming, and Pikes Peak, Colorado, 

and probably elsewhere in the Rocky Mountains and adjacent high plains.

According to Goodman:3

James mentioned Pinus resinosa in his diary on July 10 (erroneously as July 

11) [1820]. He very possibly had seen this pine the day before in Douglas 

County Colorado and certainly had seen it from Elephant Rock (his Castle 

Rock) to his campsite near the Air Force Academy, El Paso County.

James failed to collect any specimens for identification by others.

2 Lauria, F. 1995. Personal communication. Naturhistorische Museum Wien, Vienna, Austria.

3 Goodman, G.J. 1996. Personal communication. Department of Botany and Microbiology, 

University of Oklahoma, Norman, Oklahoma.
5

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Returning to Lauria’s explanations: 

When John Torrey (1828) determined and listed some of the plants already 

reported by James, it was not he who misapplied Pinus resinosa for P. 

ponderosa. In the absence of any material, he had to rely on James’ published account (1823) and on his list of plants (1825). However, Torrey’s 

repetition of “Pinus resinosa” misapplied for Pinus ponderosa is at the 

origin of Pinus resinosa Torrey, reported as a synonym of P. ponderosa by 

G.B. Sudworth (1897) and C.S. Sargent (1898).

David Douglas repeatedly made the same mistake in the Pacific Northwest. In 

“An account of a new species of Pinus (lambertiana Dougl.), native of California,” 

Douglas (1827) wrote: 

The trees do not form dense forests as most of the other Pines which 

clothe the face of North-west America, but like Pinus resinosa (actually P. 

ponderosa), which grows among them, they are scattered singly over the 

plains...

In the first publication of extracts of his journal of travels (1836: 108), he wrote 

on April 19, 1826: while traveling by boat up the Columbia River: 

Many kinds of Pine are seen on the banks, three species particularly,—

P. resinosa (actually P. ponderosa), a Pinus, very similar to P. taxifolia

[actually Pseudotsuga menziesii (Mirb.) Franco] of the coast, and P. Larix

(actually Larix occidentalis Nutt.), ...

His first collection of ponderosa pine (as host of a new mistletoe, or 

Arceuthobium) also was misidentified in the field as Pinus resinosa; 

the time was either 11th or 12th of May, 1826; the place was “the old 

Establishment” on the “Spokan (sic) River,” presumably near what is 

now Spokane, Washington.

Lauria deduced that after returning to London: 

... between April and July 1829 ... Douglas concluded he had a new pine 

among his specimens and coined for it the name Pinus ponderosa. Also 

at this stage he must have converted his annotation Pinus resinosa to 

Pinus ponderosa on his herbarium-sheet of Arceuthobium.

At that time, Douglas must also have converted the record in his journal 

entry of May 1826, for it reads: ‘I also saw a new Pinus (P. ponderosa) 

and two kinds of Misseltoe (sic), one large and growing on this Pine; ...’ 

(Douglas 1836: 111). This then is the source of the specific epithet Pinus 

ponderosa, named for its heavy wood. Douglas never described the foliage, 

immature cone, or seeds that he carried back to Edinburgh, Scotland.
6

RESEARCH PAPER PSW-RP-264

Loudon (1830: 387) listed the species, credited its name to Douglas in 1828 (not 

1826), but also failed to describe it.

The first valid description of Pinus ponderosa dates from the scanty Englishlanguage characterization, by a Scottish nurseryman, Charles Lawson, in Lawson 

and Son (1836). Described is an 8-year-old tree, lacking cones, grown from 

Douglas’ seed, which Lauria4 notes had been sown in gardens of the Horticultural 

Society of London. 

Lawson did not designate a holotype. Probably following Louden, he attributed 

the species to David Douglas in 1828. Therefore, Pinus ponderosa Douglas ex C. 

Lawson (1836) is the correct name and citation.

The publication in which the description appears could be attributed to “Peter 

Lawson and Son” (1836) if only knowledge internal to that document were considered. I have accepted Lauria’s5

 recommendation that the authority for this name 

should be C. Lawson based on Lauria’s external knowledge:

After the death of Peter Lawson in 1820 (years before Douglas’ trip to 

collect in North America), the firm continued to be called Peter Lawson and 

Son, but was exclusively run by Charles Lawson. “Agriculturists Manual” 

was issued by the firm with its composite name, but the author was clearly 

Charles Lawson alone. ...

According to Lauria (who made a fruitless search in the United Kingdom in 

1992), there is neither a holotype nor any other specimen for Pinus ponderosa:

The tree from which Lawson’s description was made no longer exists, 

and a search of all possibly relevant herbaria (BM, CGE, E, K, OXF) (sic) 

revealed no herbarium material from it, so no lectotype can be chosen. A 

correct typification therefore requires the determination of the origin of 

Douglas’ seeds from which also Lawson’s tree was grown. Douglas was not 

very informative in this respect, but does state that he did not personally 

collect it (Douglas 1914: 205). ... In conclusion, John Work ... a traveling 

trader for the Hudson Bay Company ... may have collected the requested 

seeds of Pinus ponderosa somewhere on Pend Oreille River, or he may 

have returned in time to collect them at Kettle Falls, or possibly elsewhere 

on his travels. 

It is not now possible to determine where from historical evidence. ... 

Douglas met John Work again at Kettle Falls in April 1827 on his return 

trip overland to Hudson Bay (Douglas 1914: 246) and it is presumed here 

4 See footnote 2.

5 See footnote 2.
7

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

that Work on this occasion handed over to Douglas the seeds he was able to 

gather in October of the previous year. However, it is certain that Douglas, 

on his return in October 1827, among other species also brought to Britain 

seeds of Pinus ponderosa ... .

A number of the trees grown from this seed still survive in British arboreta... . 

These are of course of the same seed lot from which Lawson described his tree, 

and so botanically closely comparable. Most of these trees were studied by the 

author (Lauria) in spring 1992; they all appear to be quite homogeneous in their 

botanical characters, and will presumably have shared these traits with Lawson’s tree. This finally enables the determination of the true identity of Pinus 

ponderosa, as meant by Douglas and defined by Lawson, ... also allowing the 

designation of a neotype.

Specific and Varietal Epithets

Descriptions under several specific and varietal epithets attest to the geographic 

diversity of ponderosa pine. On August 24, 1846, Hartweg (1847) discovered a 

luxuriant form, growing in a very small stand at what now is called Bonny Doon, 

just north of Santa Cruz, California. Hartweg (1848p. 221, 223, 225) later found 

the same pine in foothills of Sierra Nevada along Bear Creek (now Bear River, east 

of Wheatland, California). His published description was under the name Pinus

benthamiana Hart. Both Vasey (1876) and Lemmon (1888) considered this form 

to be P. ponderosa var. benthamiana (Hart.) Vasey. Trees growing at Bonny Doon 

were studied by Callaham (2013) and found to be indistinguishable taxonomically 

from other Pacific ponderosa pines, growing from southern California northward 

through western Oregon to Puget Sound.

Andrew Murray (1855) described two new species, Pinus beardsleyi A. Murr. 

and Pinus craigana A. Murr., from two collections made by his brother William 

Murray. The collections were separated by 1,000 feet of elevation, near the top of a 

mountain6

 at about 41° N in northern California. He noted that his two new species 

“seem to have more affinity with P. Benthamiana than any other described species.”

Lauria, in 1992, searched for, but did not find at either Kew or Edinburgh, surviving type specimens from these two collections; his search disclosed that George 

Engelmann, in 1869, had acquired material from these collections and 

6 See 2. According to Lauria, the location was Scott Mountain, approximately 39°39' N, 

longitude 122° 37' 42'' W. The summit, at 6,829 feet elevation, is the meeting point of 

not only Siskiyou, Trinity, and Shasta Counties, but also of Klamath, Trinity, and Shasta 

National Forests.
8

RESEARCH PAPER PSW-RP-264

“... identified the material of both of these specimens (sterile shoots) as belonging to 

Pinus ponderosa.”7 In fact, this material merely is representative of morphological 

variability found either among individual trees within a stand or associated with 

elevational change (Callaham and Liddicoet 1961, Conkle 1973).

Lemmon (1889) designated darker, young, rapid-growing populations of this 

form, growing in the very best sites of the Sierra Nevada, as P. ponderosa var. 

nigricans Lemmon. He wrote: “This form is generally found in company with the 

larger, typical, whitish-barked trees, but in moister localities.” He failed to recognize that these “black-Jacks” (a term used by loggers) were merely younger trees 

(probably second-growth following widespread cutting during California’s Gold 

Rush) that would mature into the large old trees with yellowish-tan plated bark 

found in the Sierra Nevada.

Wislizenus (1848, p. 17), on June 25, 1846, on the Santa Fe Trail in New 

Mexico, reported a new variety of what is now ponderosa pine (McKelvey 1955). 

He first found it on the east side of Sangre de Cristo Mountains, along Gallinas 

Creek, south of Las Vegas en route to a campsite, probably now Romeroville.8 9 Dr. 

Wislizenus noted on the type specimen at Missouri Botanical Garden, “The most 

common pine ... begin about Rock creek (sic) to Santa Fe.” 

Engelmann (1848) described his specimens as Pinus brachyptera Engelm. 

Lemmon (1888) reducing this species to P. ponderosa var. brachyptera (Engelm.) 

wrote: “This pine was so named by Dr. Engelmann, from a mistaken impression 

that the seed wings were very short.” [However, it was Lemmon, not Engelmann, 

who erred, for this taxon does have very short seed wings (Callaham 2013)]. Two 

names, Pinus brachyptera Engelm. (1848) and P. ponderosa var. brachyptera

(Engelm.) Lemmon (1888), were applied briefly to the form found on the high plateau of northern Arizona and New Mexico and probably extending southward into 

the northern states of Mexico. However, for most of the 20th century, trees growing 

in the Southwest have been called P. ponderosa var. scopulorum.

Engelmann (1879) [1880] designated “P. ponderosa of the Rocky Mountain 

floras” as P. ponderosa var. scopulorum Engelm. in a book by Sereno Watson. 

Lemmon (1897) elevated this variety to Pinus scopulorum (Engelm.) Lemmon. 

Edward Murray (1982), a century later, elevated Engelmann’s variety to 

a subspecies.

7 Attachment, dated August 1992, to personal communication from Friedrich Lauria, 

Naturhistorische Museum Wien, Vienna, Austria, February 28, 1994. 

8 Salazar, R.J. 1991. Personal communication. Chief, Archival Services, State Records 

Center and Archives, Santa Fe, NM.

9 Read, R.A. 1992. Personal communication. Read stated that his sample number 864 was 

from Romeroville, the site of the original discovery by Wislizenus.
9

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Lauria (1991), an authority on Pinus subsect. Ponderosae, was 

distraught over:

... inconsistencies between the vast amount of data already available on 

the group and its present taxonomic arrangement. By and by it becomes 

apparent that a variety of profound misconceptions deeply rooted in the 

minds of modern researchers in this particular field is responsible for the 

fact that the pattern of variability and diversity is still poorly understood 

in Pinus ponderosa, in the Ponderosa–complex, and in the Ponderosae in 

general... . (p. 137) The controversy on the geographic origin of Pinus ponderosa as a whole perhaps also illustrates that Pinus ponderosa sensu lato

of the Pacific Northwest appears yet not to have been adequately surveyed 

botanically, and that this “race” [Weidman’s (1939) north plateau called 

Columbia here] and Sierra Nevada western slope ponderosa pine, in fact 

represent entirely different things, actually entities too different in several 

respects, and the northern race itself too incoherent a group, to be termed 

“races” of only a single taxon.

Lauria (1996) lamented the need for a taxonomic review of Pinus ponderosa

sensu lato. The study reported here is thought to fulfill his desire for a comprehensive, range-wide review of the species, but admittedly only of its range north 

of Mexico.

Washoe Pine

Washoe pine and its relationship to ponderosa pine require special attention here. 

Geneticists at the Institute of Forest Genetics (IFG), Placerville, California, found 

and sampled a unique population of ponderosa pine growing at very high elevation, 

just east of the summit of Mount Rose, north of Lake Tahoe, Nevada. It differed 

from nearby Pacific ponderosa pine by its very small, ovoid cones and short, thick 

needles. After the director of IFG, Palmer Stockwell, showed the population to 

Professor Herbert Mason, University of California, Mason decided its differences 

from ponderosa pine warranted its designation as Pinus washoensis H. Mason & 

Stockw. (Mason and Stockwell 1945).

Haller (1961) reported Washoe pine from the Warner Mountains in northeastern 

California and described Washoe pine as a “probable introgressant of Pinus ponderosa in northeastern California ...”

After studying Washoe pine in California and Oregon, Haller (1965) wrote: “In 

view of the morphological continuum between P. ponderosa and P. washoensis in 

many localities, the status of the latter as a species seems questionable.”

Ting (1966) described Washoe pine as a variety of ponderosa pine. Murray 

(1982) arbitrarily elevated Ting’s variety to the rank of subspecies.
10

RESEARCH PAPER PSW-RP-264

Smith (1967, 1971) concluded, based on monoterpenes in xylem oleoresin, that 

Washoe pine may be most closely related to Rocky Mountains ponderosa pine, 

which he later found to be chemically indistinguishable from Columbia ponderosa 

pine (Smith 1977).

Critchfield (1984) drew three conclusions: Washoe pine crosses freely with 

Rocky Mountains ponderosa pine; it is morphologically distinct and partially 

isolated genetically from Pacific ponderosa pine; it most resembles and may be a 

late pleistocene offshoot of Columbia ponderosa pine.

Lauria (1997), from his scholarly study of its taxonomic status, concluded: 

“Pinus washoensis ... was found to be identical (conspecific) with P. ponderosa ... 

‘North Plateau race’ of P. ponderosa var. ponderosa.”

Brayshaw (1997) described Washoe and ponderosa pines as he found them on 

Promontory Hill near Merritt, British Columbia, Canada.

Rehfeldt (1999a) concluded that Washoe pine and North Plateau race (Columbia 

ponderosa pine) were synonymous.

Excluded Taxa

Several taxa in genus Pinus now regarded as distinct species sometimes have been 

united with ponderosa pine. Taxa hereby excluded from Pinus ponderosa are as 

follows:

• Pinus apacheca Lemmon, Erythea 2:103, t. 3. 1894.—syn. of P. ponderosa 

fide G.R. Shaw 1914. = Pinus engelmannii Carrière fide Critchfield and Little 

(1966), Little (1979).

• Pinus arizonica Engelmann (1878) in Wheeler, Rpt. U.S. Geogr. Surv. 6: 

260.—syn. of P. ponderosa fide G.R. Shaw (1909, 1914).—Type: Arizona, 

Santa Rita Mountains, 7,000 feet, 1874. J.F. Rothrock, 652 (holotype: MO, 

3377654). Accepted as Pinus arizonica by Lemmon (1889), C. Sargent 

(1898), Peloquin (1984), Conkle and Critchfield (1988), and Rehfeldt (1993).

• Pinus deflexa Torrey in Emory, Rpt. U.S. Mex. Boundary Surv. 2:1, 209, t. 

56. 1859.—syn. of P. ponderosa fide G.R. Shaw (1914). = Pinus jeffreyi var. 

deflexa (Torrey) Lemmon, Rpt. Calif. St. Bd. Forestry, 74 (1888). Described by 

Lemmon as “In the Sierra and southward at usually higher altitues (sic), often 

very large trees. Timber less sappy. Bark reddish. Yearling cones purple.”

• Pinus engelmannii Carrière, Rev. Hort. 4(3): 227. 1854. “engelmanni.” (A 

renaming of P. macrophylla Engelm. 1848, not P. macrophylla Lindley 

1839.)—syn. of P. ponderosa fide G.R. Shaw (1914). Accepted as Pinus 

engelmannii Carrière by Critchfield and Little (1966), Little (1979).

• Pinus jeffreyi Grev. & Balf. in A. Murray (often cited as “Oregon 

Committee”), Bot. Exped. Oregon [Rpt. 8] 2, pl. 1853.—syn. of P. 
11

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

ponderosa fide G.R. Shaw (1914). Accepted as Pinus jeffreyi by Lemmon 

(1888), Sudworth (1897), Mirov (1929), Righter and Duffield (1951), Duffield 

(1952), Haller (1962), Critchfield and Little (1966), and Little (1979)].

• Pinus jeffreyi var. ambigua Lemmon, Bull. Calif. State Board For. 7:11. 

1889—P. jeffreyi var. montana. Lemmon (1895), Handb. West-Amer. 

Cone-Bearers, ed. 3, 35, nom. superfl., illegit.—syn. of P. ponderosa fide

Sudworth (1897). = Pinus ponderosa fide C. Sargent 1898. Lemmon (1889) 

wrote: “A pine noted by Canby and Sargent, in Flathead Lake Valley, 

Montana, as being ‘the prevailing tree of the valley, with purple cones, and 

long glaucous foliage.’ This tree probably belongs with the jeffreyi group 

of forms, although Professor Sargent doubtfully referred it to P. ponderosa

in his report of ‘Forest Trees of America,’ in the 10th United States Census, 

page 193, 1884.” Pinus jeffreyi does not occur in Montana fide Critchfield 

and Little (1966). The study reported by Callaham (2013) included a plot at 

the north end of Flathead Lake Valley, and trees from that plot were typical 

of P. ponderosa subsp. ponderosa.

• Pinus latifolia Sargent, Garden and Forest 2: 496, pl. 135. 1889 (sometimes 

cited as P. latifolia Mayr10).—syn. of P. ponderosa fide G.R. Shaw (1914). = 

Pinus engelmannii Carrière fide Lemmon (1893) and Critchfield and Little 

(1966), Little (1979).

• Pinus macrophylla Engelm. in Wislizenus, Mem. Tour No. Mex. (Senate 

Misc. Publ. 26, 30th U.S. Congress) 103, 1848, not Lindley 1839 = Pinus 

engelmannii Carrière.

• Pinus mayriana Sudworth, Bulletin of the U.S. Department of Agriculture 

Division of Forestry 14:21. 1897.—syn. of P. ponderosa fide G.R. Shaw 

(1914) = Pinus engelmannii Carrière (see P. ponderosa var. mayriana below).

• Pinus nootkatensis Hort. ex Manetti (1844), nomen nudum, Caesarei Regii 

Horti Modiciam, Sup. Primum, Mediolani 28.—syn. of P. ponderosa fide

Gordon (1862) and Sudworth (1897).

• Pinus parryana Gordon (1858), Pinet. 202, not Engelm.—syn. of P. ponderosa fide G.R. Shaw (1914). = Pinus attenuata Lemmon.

• Pinus peninsularis Lemmon, W. Amer. Conebear. 114. 1900.— syn. of P. 

ponderosa fide G.R. Shaw (1914). Duffield and Cumming (1949) failed to 

find Pinus ponderosa in Baja California. = Pinus jeffreyi var. peninsularis

Lemmon (1888). Cited by Lemmon as “On the highest central range of 

mountains in the Peninsula of Lower California.”

10 See footnote 2.
12

RESEARCH PAPER PSW-RP-264

• Pinus ponderosa var. arizonica (Engelm. in Wheeler) G.R. Shaw, Pines 

Mex., Publ. Arnold Arbor. 1, 24, pl. 17, figs. 4–5. 1909. = Pinus arizonica

Engelm. in Wheeler (see Pinus arizonica above).

• Pinus ponderosa subsp. arizonica (Engelm. in Wheeler) E. Murray, Kalmia 

12:23. 1982. = Pinus arizonica (see Pinus arizonica above).

• Pinus ponderosa subsp. coulteri (D. Don) E. Murray, Kalmia 12:23. 1982. 

= Pinus coulteri D. Don [cf., G.R. Shaw (1914), Righter and Duffield (1951), 

Duffield (1952), Critchfield and Little (1966), Little and Critchfield (1969), 

Little (1979), Index Kewensis, Supl. XVIII, 244. 1987].

• Pinus ponderosa var. jeffreyi (Grev. & Balf. in A. Murray) Vasey, 

Catalogue of Forest Trees, U.S. Government Printing Office. 30. 1876. = 

Pinus jeffreyi (see Pinus jeffreyi above).

• Pinus ponderosa subsp. jeffreyi (Grev. & Balf. in A. Murray) E. Murray, 

Kalmia 12: 23. 1982. = Pinus jeffreyi (see Pinus jeffreyi above).

• Pinus ponderosa var. macrophylla (Engelm.) G.R. Shaw, Pines Mex. Publ. 

Arnold Arb. 1, 24, pl. 17, figs. 2–3, 6. 1909,—based on Pinus macrophylla

(see above). = Pinus engelmannii Carrière.

• Pinus ponderosa var. mayriana (Sudworth) Sargent, Silva No. Amer. 11:81. 

1898—syn. of Pinus latifolia fide C. Sargent (1889) and of Pinus mayriana 

fide Sudworth (1897)—According to Sargent (1898), this variety (or species) is based on a collection from an isolated single tree growing at lower 

elevation than typical southwestern ponderosa pine on the southern slopes 

of the Santa Rita Mountains in southeastern Arizona. = Pinus engelmannii

Carrière fide Lemmon (1893).

• Pinus ponderosa var. stormiae (Martinez) Silba, Phytologia 68: 59. 1990. 

Silba transferred Pinus arizonica var. stormiae Martinez to Pinus ponderosa and suggested that it may be distributed “possibly also in Chisos 

Mountains, Texas, United States.” Trees having three to five needles per 

fascicle have been observed in the Chisos Mountains by Little.11 Specimens 

from one plot in the Chisos Mountains, collected for the study reported 

by Callaham (2013), were typical of P. ponderosa subsp. brachyptera. 

Consideration of the variation in ponderosa pine that may exist in Mexico 

is beyond the scope of this paper. Furthermore, Silba’s description of his 

taxon indicates to me that it should not be included under Pinus ponderosa

because needles are in fascicles of 3 to 5, not 3 as in southwestern ponderosa pine, and female cones are (1) too long, (2) curved rather than either 

11 Little, E.L., Jr. 1998. Personal communication. Dendrologist, retired, U.S. Department of 

Agriculture, Forest Service, Washington, DC.
13

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

straight or only slightly curved, and (3) persistent rather than deciduous 

during the first winter after ripening.

• Pinus sinclairii Hooker & Arnott, Bot. Beechey Voy. 392, t. 93. London, 

1840.—(according to Lauria,12 sometimes written as sinclaireana and sinclairiana Carrière, Traité Gén. Conif. Paris, 1855, 355)—syn. of P. ponderosa fide Sudworth 1897. = Pinus radiata D. Don fide C. Sargent (1898).

Genetic Investigations

Foresters and forest geneticists have grown and compared ponderosa pines collected from different provenances in “common garden” plantings since 1910 (Wang 

1977). Only their findings related to differentiation of races of ponderosa pine are 

discussed here.

Kempff (1928) from 11- to 17-year-old plantings near Priest River, Idaho, found: 

(using names defined herein) Pacific (Mount Shasta) source had no resistance to 

deep continental frost; North Plateau race was superior to Rocky Mountains race; 

Rocky Mountains race was superior to Southwestern race.

Larson (1967) studied responses of 6-weeks-old ponderosa pine seedlings 

from southwestern (Coconino National Forest), Pacific (Angeles National Forest, 

Critchfield’s Southern California race), and Rocky Mountains (Black Hills) races. 

Seedlings were grown under combinations of constant air and soil temperatures 

and combinations of day and night temperatures. Root growth responded more to 

soil temperature. Top growth responded more to air temperature. Epicotyl length, 

root penetration, number of lateral roots, and dry weight of roots were correlated 

with daily degree hours of each treatment. Source of seed had a pronounced effect 

on final seedling size. Pacific seedlings were largest. Black Hills seedlings 

were smallest.

LaFarge (1977) measured stem taper in Wells’ 10-year-old ponderosa pine 

plantation in Michigan. He found that Pacific ponderosa pines were more cylindrical (less taper) vs. more conical ponderosa var. scopulorum (more taper).

Moore and Kidd (1982) studied germination under induced moisture stress 

using seeds collected from 76 ponderosa pines from 11 seed zones throughout 

Colorado. They concluded that two seed zones in the dry plains and foothills east 

of the Front Range (central high plains race) were adapted to more xeric conditions. 

Sources adapted to the most mesic conditions represented seed zones in the southwest part of Colorado (Four Corners transition zone, strongly influenced by summer monsoonal precipitation). The remaining seed sources represented seed zones 

in the central, mountainous part of Colorado (Rocky Mountains race).

12 See footnote 2.
14

RESEARCH PAPER PSW-RP-264

Read (1980, 1983) studied 24 characteristics of seedlings (grown 3 years near 

Hastings, Nebraska) from 80 ponderosa pines growing in the Great Plains and 

adjacent Rocky Mountain states. Thirteen traits provided a basis for grouping into 

nine geographical clusters. Two of his clusters, California and the North Plateau 

(Oregon, Washington, Idaho, and western Montana) fit the description of Pinus ponderosa var. ponderosa. Other clusters, east of the Continental Divide and including 

one Arizona source west of that divide, were described as P. ponderosa var. scopulorum and divided into: (1) Transition between the two varieties in west-central 

Montana, (2) Central Montana, (3) Central Rockies from north-central Wyoming to 

south-central Colorado, (4) Black Hills and surrounding High Plains from eastern 

Montana to western Nebraska, (5) Easternmost low altitude in northern Nebraska, 

(6) Colorado Plains east of the Front Range, and (7) Southern Rockies from extreme 

southern Colorado through central New Mexico and Arizona.

Read (1983) reported on attributes of his 10-year-old progenies planted near 

Hastings, Nebraska. Read and Sprackling (1981), in Read’s 13-year-old planting, 

observed that North Plateau and southwestern races suffered very heavy damage 

by marble-sized hail. Rocky Mountains and central High Plains sources suffered 

only moderate to light damage. Van Haverbake (1988) reported 15-year results of 

Read’s study.

Conkle and Critchfield (1988)—after summarizing information on geographic 

distribution of the species and inherent variation associated with geography—recognized two varieties, six geographic races, five ecotypes, or seven to nine statistically derived geographical clusters. They covered variation in:

• Morphology, both in situ and that expressed in “common garden” plantings.

• Monoterpenes in the turpentine fraction of oleoresin exuded from xylem.

• Allozymes.

Most importantly, they summarized attempts to hybridize ponderosa pine that 

identified both its genetic isolation from related species and genetic isolation among 

its races.

Earlier, Critchfield (1984) summarized what was known about genetic barriers 

to crossing within the species. However, he adequately tested crossability for only 

one of ten possible interracial crosses.

He found genetic barriers that limited crosses between Pacific and Rocky 

Mountains races to 35 percent. Crossability from his few crosses between Pacific 

and North Plateau races appeared on the order of 50 percent. He also concluded 

there was no evidence for phylogenetic affinity between southwestern and Pacific 

races. He was first to map races and transition zones as were delineated by Callaham (2013).
15

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Linhart et al. (1989) studied allozymes from a small number of individuals 

resulting from Pacific x Pacific and Pacific x Rocky Mountains parents. Niebling 

and Conkle (1990) surveyed allozyme variation to determine the relationship 

between Pacific race and Washoe pine, the latter considered here to be synonymous 

with Columbia race. The overall conclusion was that Rocky Mountains race differed significantly from both the Pacific race and Columbia race.

Smith (1981) was first to establish the importance of color of immature cones 

for identifying typical ponderosa pine of the Columbia basin from other varieties or 

races—it being red to purple and all others being green to yellow-green.

Rehfeldt (1986a, 1986b, 1990, 1991, 1993) studied 353 seedling progenies, 

representing populations of ponderosa pines along a broad transect from Canada to 

Mexico. His comprehensive and important provenance studies—almost entirely of 

non-taxonomic characters—demonstrated:

• Patterns of variation within races of ponderosa pine were continuous 

and clinal.

• These patterns repeated among races as latitude, longitude, and 

elevation changed.

Finding clinal patterns of variation, sometimes very steep, wherever he looked 

within ponderosa pine, he ignored the existence of subspecific taxa within this 

complex species. He was frustrated that taxonomists were unable, some unwilling, 

to recognize the importance of elevational patterns of variability. Suspecting they 

simply did not know how to treat it; he wrote:

...enormous differences, both genetic and phenotypic, separate geographically distant populations, and, therefore, it is useful to have a name available; perhaps a map without lines on it would be more descriptive of the 

actual situation.13

Being fully sympathetic with Rehfeldt’s viewpoints, I also recognize the 

necessity of placing lines or shaded bands, demarking taxa, on maps where they are 

warranted by significant variation in taxonomic characters.

Rehfeldt et al. (1996) and Rehfeldt (1999b) reported on cones and foliage from 

295 trees of Ponderosae taxa in Arizona, New Mexico, and Texas. What they and 

he classified and labeled as Pinus ponderosa var. scopulorum was synonymous with 

southwestern ponderosa pine as described and labeled herein.

13 Rehfeldt, G. 1998. Personal communication. Geneticist, U.S. Department of Agriculture, 

Forest Service, Intermountain Research Station, Moscow, ID.
16

RESEARCH PAPER PSW-RP-264

Smith (1977) recognized and mapped, within ponderosa pine, five regions 

and four transition zones based on frequency of five major monoterpenes found in 

xylem oleoresin. He proposed and established through further research:14

Absence or relative amount of each of these monoterpenes is controlled by 

a single gene with two additive alleles at the locus. The relative level of a 

monoterpene found in a population then depends upon the frequency of two 

alleles within that population.

Smith (1977) presented evidence for a southern California race (his San Jacinto 

Region) south of his narrow transition zone in the Transverse Range and Tehachapi 

Mountains. Smith divided Critchfield’s southwestern ponderosa pine into two 

regions and a transition zone.

Smith found no chemical evidence for subdividing Rocky Mountains ponderosa 

pine or for distinguishing it from typical Columbia ponderosa pine. However, after 

plotting Smith’s data, Read15 found slight but recognizable differences in proportion of beta-pinene in monoterpenes between Rocky Mountains ponderosa pine (21 

to 28 percent) and Columbia ponderosa pine (14 to 22 percent).

Prompted by Read’s finding, Callaham (2013) reexamined Smith’s data and 

found that northern Rocky Mountains ponderosa pine differed significantly from 

Columbia ponderosa pine, growing to the west, by having more alpha-pinene, more 

beta-pinene, less delta-3-carene, and less myrcene. Western Rocky Mountains ponderosa pine (in Utah and Nevada) differed from Columbia ponderosa pine, growing 

to the north, by having more alpha-pinene, less delta-3-carene, and less myrcene.

Rotach in his unpublished doctoral dissertation (Swiss Federal Institute of 

Technology, Zurich, 1997) came to the conclusion that Critchfield’s demarcation 

line along the Cascade crest was unwarranted and that “purported” races on both 

sides of the crest had the same evolutionary history. He studied patterns of genetic 

variation in allozymes and seedling quantitative traits.

Sorenson et al. (2001) studied patterns of adaptive variation within and 

between two parapatric races of ponderosa pine (Pacific and North Plateau) in 

southern Oregon.

(Their) data supported a narrow, adaptive transition for a complex of traits 

related to cold hardiness and provided evidence that plant vigor traits were 

more closely adapted to environments in the North Plateau than in the 

Pacific region.

14 Smith, R.H. 1995. Personal communication. Retired entomologist, U.S. Department of 

Agriculture, Forest Service, Intermountain Research Station, Moscow, ID. 

15 Personal communication to W.B. Critchfield, September 21, 1982.
17

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Haller and Vivrette (2011) assigned a new varietal name pacifica Haller to the 

Pacific race of ponderosa pine.

Callaham (2013) identified five distinct races and intervening transition zones of 

ponderosa pine in geographic regions. Samples for study were collected from plots 

located at elevational intervals along latitudinal transects (fig. 2). Data included:

• Fifteen characteristics of branches and foliage from 10 or fewer trees on 147 

plots.

• Three characteristics of cones from 120 of those plots

• Seven characteristics of seeds from 78 of those plots.

Callaham also collected data on foliage and branch characteristics from three 

common-garden plantings of 10 widespread provenances. Characteristics found to 

be useful discriminators among Callaham’s five races included:

• Branches per whorl

• Foliated length of branch

• Length and thickness of needles

• Proportional length of needle fascicles

• Number of needles per fascicle

• Number of hypodermal cell layers in corners of needles

• Number of adaxial resin ducts in needles

• Cone form

• Seed form

• Length of seed wing

Needle length was picked as a discriminator of all races. Number of hypodermal cell layers was picked in four of five comparisons. Needle thickness was a 

discriminator in two of five comparisons. All characteristics used to discriminate 

races exhibited significant inherent variation associated with provenance. Only 

branch angle discriminated the Pacific race from the Southwestern race.

Data from Weidman’s (1939) provenance study showed that needle length, 

needle thickness, and number of hypodermal cell layers were under strongest 

genetic control. Substantial differences among races were deemed to warrant their 

being given separate taxonomic identities.

Implications for Taxonomy

The magnitude and significance of inherent patterns of variation within ponderosa 

pine provide bases for decisions about infraspecific taxonomy. Designation of 

five subspecies within ponderosa pine is supported primarily by previously cited 

findings of inherent variation in morphology and xylem monoterpenes, and to a 
18

RESEARCH PAPER PSW-RP-264

Figure 2—Distribution of ponderosa pine and 147 plots established for Callaham’s (2013) rangewide study.
19

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

lesser extent by evidence of partial genetic barriers to crossing and of differences in 

allozymes among three subspecies.

The following text starts with ponderosa pine’s taxonomy and a general 

description of characteristics of the species. Taxonomy—including type specimens, 

attributable synonyms, cultivars, and sports—is followed by description of morphological and monoterpene characters with contrasts in characters among subspecies. 

Successive sections of the text treat each of five subspecies in a parallel manner.

• Pinus ponderosa Douglas ex C. Lawson, Agriculturist’s Manual p. 354. 

1836.—Pinus ponderosa Douglas ex Loud., Hort. Brit. p. 387. 1830, nomen 

nudum,—Pinus ponderosa Douglas, Companion Bot. Mag. 2:111, 141. 1836, 

nomen nudum. Type unknown, see neotype under P. ponderosa subsp. ponderosa below.

• Pinus ponderosa tortuosa E. -A Carrière, Traité Gén. Conif., Paris, ed. 2, 

1867, p. 445, a sport of unknown provenance having twisted branches.

• Pinus ponderosa f. malleti L. Beissner, Mitt. Deutsch. Dendrol. Ges. 1907, 

p. 105, a horticultural selection of unknown provenance having reddish 

bark and long needles.

• Pinus ponderosa var. parryana (Gordon) W. Robinson, Fl. & Sylva 3, 

1905, p. 104, a sport of unknown provenance having numerous, thickly 

foliated branches, leaves long and drooping, found at Highnam Court near 

Gloucester, United Kingdom.

• Pinus ponderosa var. sinclairiana (Gordon) W. Robinson, Fl. & Sylva 

3, 1905, p. 104, a sport of unknown provenance having many suberect 

branches, foliated at tips with short, thick, quite glaucous needles, found at 

Pampesford Hall near Cambridge, United Kingdom.

A botanical description of the species could be as brief as the original 130 

words by P. Lawson and Son (1836) or as long as the five pages written by Sargent 

(1898). The following description draws heavily from statements and data provided 

by Lemmon (1888, 1889), Sargent (1898), Haller (1962), Critchfield (1984), Peloquin 

(1984), and Callaham (2013). This description covers not only unique characteristics 

of the species but also discloses variability associated with geography for each 

character. The following description should facilitate identification of ponderosa 

pine observed in or collected from native stands:

• Trees to heights of 80 m (Pacific region).

• Stem usually straight and robust; branches relatively thick and persistent; 

usually one whorl per year; usually 3 to 6 in a whorl (2 to 5 in the Rocky 

Mountains and 1 to 2 in the central High Plains); inserted at a wide to narrow angle from apex of the stem of young trees (average angle, 56° in the 
20

RESEARCH PAPER PSW-RP-264

Pacific region, 51° in the Columbia Basin, 48° in the Southwest, 50° in the 

Rocky Mountains, 36° in the central High Plains).

• Bark forms third to fifth year; when tree is mature, with many vertical 

fissures and furrows and lacking plates, color dark brown, or dark gray, 

to black; when tree is overmature (older than 150 to 200 years), thick 

with widely separated and relatively shallow fissures resulting in large 

plates, color light whitish yellow to yellowish tan in the Pacific region and 

Columbia Basin, bright cinnamon red in the central High Plains, reddish brown to cinnamon brown in the Southwest; inner abscission layer 

of individual scales soft and bright yellow or yellowish-tan in color in the 

Pacific region and the Columbia Basin, reddish-brown to cinnamon in the 

Southwest, bright cinnamon-red in the central High Plains; tends to be 

scaly, less fissured, and black or gray in appearance at lower elevations.

• Xylem oleoresin odor (discernible in bark crevices warmed by the sun), 

usually smells like commercial turpentine, in the Pacific region sometimes 

of lemon rind but never of vanilla or pineapple (characteristic of P. jeffreyi), 

usually abundant presence of the monoterpene delta 3-carene (Mirov 1961, 

Smith 1977).

• Secondary needles finely serrate; sharp-tipped; finely lined with stomata on 

all faces, waxy deposits in stomata appear as lines of small, disconnected, 

white dots; 144 to 243 mm long and deep yellowish-green in the Pacific 

region; 130 to 205 mm long and green to blue-green in the Columbia Basin; 

92 to 144 mm long and green to blue-green in the Rocky Mountains; 148 

to 179 mm long and blue-green in the central High Plains; 112 to 198 mm 

and green to blue-green in the Southwest; in all regions, paler and shorter 

at higher elevations and under xeric conditions; generally not glaucous, but 

becoming glaucous at higher elevations and with the onset of winter; ranging from flexible and in fascicles of three (in the Pacific region, Columbia 

Basin, and Southwest) to stiff and in fascicles of two or of two and three (in 

the Rocky Mountains, and High Plains); remaining green on stem an average of 3 to 6 years (ranging 1.4 to 6.5 years in the Pacific region, 2.2 to 7.6 

in the Columbia Basin, 2.5 to 5.9 in the Southwest, 3.6 to 7.9 in the Rocky 

Mountains, 4.1 to 5.0 in the central High Plains), remaining green longer 

at higher elevations; persisting on branch only a few years, giving a tufted 

appearance to branches, but extending farther along the branch, giving a foxtail appearance, at higher elevations in the Rocky Mountains and particularly 

so in the central High Plains; with two fibrovascular bundles surrounded 

by a single-celled layer of endodermal cells having thick outer walls; 3 to 7 
21

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

medial resin ducts external to endoderm; enclosed at the base by sheaths of 

papery bracts that are, in the first year, 10 to 15 percent of needle length but 

that weather away to leave a thick, dark brown to black sheath only 4 to 8 

mm long on the oldest fascicles.

• Vegetative shoots elongating only once each year; in the current year, 

green or brownish green and viscid in the Pacific region and the Columbia 

Basin, brown or with white to gray waxy bloom in the Rocky Mountains 

and the central High Plains, blue or purple waxy bloom or reddish brown in 

the Southwest.

• Vegetative buds covered with ovate acute scales that are conspicuously 

fringed with fairly short, brownish hairlike projections; scales dark reddish 

brown (Pacific region) to light chestnut-brown or gray brown; scales closely 

appressed in most regions but looser in the Pacific region and the Columbia 

Basin; scales dotted with resin during summer, sometimes covered with 

resin during winter.

• Pollen cones borne in clusters of 5 to 30; long-cylindrical; variable in 

length and color, 35 to 90 mm and dark reddish brown to reddish purple 

in the Pacific region, 20 to 70 mm and dark red to reddish purple in the 

Columbia Basin, 17 to 50 mm and yellow, light pink, or, occasionally, red to 

purple in the Rocky Mountains, 10 to 25 mm and dark red to reddish purple 

in the central High Plains.

• Seed cones in first year 15 to 25 mm long, on stalks half as long; red on 

emergence, turning greenish brown to drab gray (in the Pacific region), 

with short, appressed, mucronate scales, prickles usually erect; when 

mature, of relatively low density; symmetrical and straight to slightly 

curved; of medium length (averaging 100 mm in the Pacific region, 89 

mm in the Columbia Basin, 75 mm in the Southwest, 71 mm in the Rocky 

Mountains and the central High Plains), varying in shape from long, ovoidtruncate (in the Pacific region, most but not all of the Columbia Basin, and 

the Southwest) to ovoid or globoid [Columbia Basin (in the neotype location 

and elsewhere), Rocky Mountains and central High Plains]; color during 

second summer variable (apple green to yellow green, but never reddish 

brown to purple in the Pacific region, polymorphic but typically reddish 

brown to dark purple, minority of trees having green in the Columbia 

Basin, green in the Southwest,16 green to reddish brown to dark purple in 

16 Personal communications from Ernest A. Kurmes, Northern Arizona University, 

Flagstaff, AZ, Ralph A. Read, retired geneticist, USDA Forest Service, and Yan B. Linhart, 

University of Colorado, Boulder, CO.
22

RESEARCH PAPER PSW-RP-264

the Rocky Mountains17and central High Plains, green cones mature to tan 

and darker pigmented cones mature to reddish or chocolate brown when 

opening on tree; subsessile and deciduous during the first winter after ripening, very short stalk and a few basal scales usually persisting temporarily 

on branch after the cone falls.

• Seed cone scales relatively few (159 in the Pacific region, 134 to 137 in the 

Columbia Basin, 112 to 141 in the Rocky Mountains); thin, narrow, slightly 

concave, and usually rounded at apex; apophysis tawny yellow to fuscous 

brown, lustrous, only slightly elevated along a transverse keel; umbo salient 

and forming base of a stout, persistent prickle usually directed outward, but 

occasionally slightly reflexed; adaxial surface (toward cone axis) slightly 

concave and dull tawny to red brown; abaxial surface typically dark brown, 

purplish, or blackish; arranged loosely in two series of spirals, one of 8 

rows and the other usually of 5 rows, but occasionally of 13 rows, each row 

at approximately right angles to the other.

• Seeds (body) dark brown or speckled; ovoid acute; rounded in cross section; width about two-thirds of length, averaging 4 to 5 mm; length, 5 to 8 

mm (6 to 8 mm in the Pacific region, the Columbia Basin, and the central 

High Plains, 5 to 7 mm in the Southwest and the Rocky Mountains).

• Seed wings thin and semitransparent, pale brown, sometimes darkly 

streaked with brown; widest at or slightly below midpoint; gradually narrowed to rounded apex; relatively long, that is, 3.3 to 4.3 times 

length of seed; average length 24.8 mm in the Pacific region, 16.6 mm in 

the Columbia Basin, 15.5 mm in the Southwest, 16.4 mm in the Rocky 

Mountains, 16.1 mm in the central High Plains.

The following descriptions emphasize differences among subspecies and do not 

repeat characteristics they all share in common as ponderosa pine. In the following 

descriptions, numerical values are means for each subspecies based upon measurements of samples from each of 10 trees at 5 to 50 plot locations and (in parentheses) range between smallest and largest means for plots within each subspecies’ 

geographic area (table 1). Means, standard errors, and ranges for all characteristics 

were calculated after excluding data from plots in bordering transition zones. In 

all cases, values for plots within transition zones were intermediate between and 

overlapping those of adjacent subspecies.

17 Linhart, Y.B. 1998. Personal communication. Professor, University of Colorado, Boulder, 

CO. Linhart stated that color was always green at low to mid elevations in the Front Range 

of Colorado; above 2,500 to 3,000 m, some trees have distinctly purple cones.
23

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Table 1—Means (with standard errors (SE) of means, plus range of plot means) derived from multiple 

measurements on each of 10 trees growing at a varying number of plot locations for in situ morphological 

characteristics of five subspecies of Pinus ponderosa

Subspecies

P. ponderosa var. critchfieldiana P. ponderosa var. ponderosa P. ponderosa var. scopulorum

Characteristic Mean 1 SE Range Plots Mean 1 SE Range Plots Mean 1 SE Range Plots

Foliage:

Years needles 3.9 0.25 1.4–6.5 30 4.7 0.14 2.2–7.6 50 5.7 0.28 3.6–7.9 23 remain green

Foliage length 25.1 2.4 7.4–52.1 30 26.2 2.2 5.1–84.6 50 21.1 1.7 11.4–42.9 23 on branch (cm)

Needle color hue 34.8 0.25 32.3–40.4 27 34.3 0.10 31.5–35.2 47 34.3 0.11 32.9–35.0 22

Needle color value 4.4 0.09 3.0–5.0 27 4.4 0.07 3.6–5.1 47 4.5 0.09 3.9–5.4 22

Needle color chroma 4.6 0.08 3.5–5.0 27 4.5 0.06 3.0–5.0 47 4.2 0.14 2.5–5.0 22

Needle length (cm) 19.8 0.44 14.4–24.3 30 16.8 0.29 13.0–20.5 48 11.2 0.27 9.2–14.4 23

Needle length/ 8.1 0.28 5.8–12.8 30 7.4 0.15 5.8–10.0 48 6.1 0.22 4.2–7.8 23 fascicle length

Needles per fascicle 3.0 0.002 2.99–3.04 30 3.0 0.002 2.97–3.07 48 2.6 0.06 2.2–3.0 23

Needle thickness 45.9 0.49 41.9–54.6 30 47.8 0.51 37.6–58.8 48 46.4 0.68 39.4–53.4 23 (arbitrary units)

Adaxial resin ducts/ 0.8 0.04 0.25–1.22 30 0.8 0.04 0.1–1.5 48 0.9 0.10 0.3–2.5 23 needle

Abaxial resin ducts/ 2.6 0.15 1.2–3.9 30 2.3 0.13 0.1–4.1 48 2.4 0.15 1.5–3.9 23 needle

Small resin ducts/ 3.2 0.19 0.9–4.9 30 2.8 0.17 0.4–5.2 48 3.1 0.25 1.8–6.4 23 needle

Hypodermal cell layers 3.2 0.04 2.7–3.7 30 3.4 0.03 2.7–3.9 48 4.1 0.05 3.6–4.4 23

Branches:

Branches per whorl 4.4 0.13 2.7–6.0 30 3.7 0.11 1.9–5.6 50 3.0 0.17 2.0–4.6 23

 Branch angle (degrees 56 1.8 30–75 30 51 1.7 30–79 50 50 2.3 31–76 23 from vertical)

Cone length (mm) 101.4 2.48 63.6–121.7 25 88.7 1.24 72.5–103.0 36 70.7 2.20 52.4–92.6 22

Cone width (mm) 77.1 1.35 56.3–88.6 25 71.6 0.73 63.6–81.4 36 61.5 1.08 53.1–69.1 22

Cone form (width/ 0.80 0.03 0.70–1.50 25 0.84 0.03 0.80–1.80 36 0.90 0.02 0.70–1.00 22 length)

Seeds:

Seed length (mm) 7.5 0.08 6.9–8.1 23 7.6 0.16 6.5–8.4 14 6.3 0.09 5.4–6.9 17

Seed width (mm) 4.9 0.05 4.3–5.3 23 4.9 0.08 4.5–5.5 14 4.1 0.05 3.6–4.6 17

Seed + wing length 32.3 0.58 24.2–37.0 23 24.8 0.62 20.2–29.5 14 22.9 0.63 18.0–27.6 17 (mm)

Seed wing widest 0.36 0.02 0.30–0.50 23 0.46 0.01 0.40–0.50 14 0.44 0.02 0.30–0.50 17 (base to tip)

Seed form 1.52 0.01 1.40–1.60 23 1.57 0.02 1.40–1.70 14 1.52 0.01 1.40–1.60 17 (length/width)

Wing length, 24.8 0.57 16.1–28.9 23 16.6 0.70 13.0–21.8 14 16.4 0.67 10.0–21.1 17 absolute (mm)

Wing length, 4.34 0.08 3.00–4.90) 23 3.26 0.10 2.90–4.10) 14 3.62 0.09 3.10–4.30 17 proportional
24

RESEARCH PAPER PSW-RP-264

Table 1—Means (with standard errors (SE) of means, plus range of plot means) 

derived from multiple measurements on each of 10 trees growing at a varying 

number of plot locations for in situ morphological characteristics of five 

subspecies of Pinus ponderosa (continued)

Subspecies

Characteristic P. ponderosa var. brachyptera P. ponderosa var. readiana

Mean 1 SE Range Plots Mean 1 SE Range Plots

Foliage:

Years needles 4.3 0.18 2.5–5.9 24 4.7 0.18 4.1–5.0 5 remain green

Foliage length 21.8 2.7 6.6–53.8 24 42.2 6.7 25.9–65.0 5 on branch (cm)

Needle color hue 34.4 0.16 32.8–36.2 24 34.6 0.27 33.5–35.0 5

Needle color value 4.8 0.13 3.7–6.1 24 4.6 0.19 4.1–5.0 5

Needle color chroma 4.0 0.16 2.4–5.0 24 4.8 0.13 4.3–5.0 5

Needle length (cm) 114.7 0.45 11.2–19.8 24 15.6 0.57 14.8–17.9 5

Needle length/ 6.4 0.26 4.5–9.9 23 9.3 0.36 8.2–10.4 5 fascicle length

Needles per fascicle 3.0 0.03 2.7–3.5 24 2.4 0.11 2.2–2.8 5

Needle thickness 44.8 0.87 34.4–51.1 24 49.7 0.61 47.4–51.0 5 (arbitrary units)

Adaxial resin ducts/ 1.2 0.09 0.7–2.4 24 1.5 0.35 0.6–2.6 5 needle

Abaxial resin ducts/ 2.4 0.18 0.8–4.4 24 3.9 0.60 2.1–5.6 5 needle

Small resin ducts/ 3.4 0.27 1.1–6.4 24 5.4 0.98 2.5–8.2 5 needle

Hypodermal cell layers 4.1 0.06 3.4–4.5 24 4.7 0.06 4.5–4.9 5

Branches:

Branches per whorl 3.4 0.25 1.6–6.6 23 1.3 0.11 1.1–1.6 5

 Branch angle (degrees 3.1 30–79 24 36 1.9 31–40 5 from vertical)

Cone length (mm) 74.9 2.51 60.2–99.2 20 71.1 2.46 64.8–77.1 5

Cone width (mm) 62.6 1.77 47.6–75.6 20 63.3 2.18 58.6–68.9 5

Cone form (width/ 0.86 0.02 0.80–1.00 20 0.90 0.03 0.80–1.00 5 length)

Seeds:

Seed length (mm) 6.4 0.18 5.1–7.4 16 7.0 0.12 6.5–7.2 5

Seed width (mm) 4.3 0.09 3.8–4.9 16 4.5 0.10 4.2–4.7 5

Seed + wing length 23.3 0.68 18.2–26.2 15 23.1 0.78 20.8–24.9 5 (mm)

Seed wing widest 0.44 0.01, 0.40–0.50 15 0.48 0.02, 0.40–0.50 5 (base to tip)

Seed form 1.48 0.02, 1.30–1.60 16 1.56 0.02, 1.50–1.60 5 (length/width)

Wing length, 15.5 1.47, 15.1–19.3 16 16.1 0.68, 14.3–17.7 5 absolute (mm)

Wing length, 3.59 0.07, 3.30–4.00 15 3.30 0.06, 3.20–3.50 5 proportional
25

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Five Subspecies

1. Pinus ponderosa Douglas ex C. Lawson subsp. ponderosa, Columbia 

ponderosa pine—

Type: The name, as used by C. Lawson, was linked to “small plants in pots... (and) 

a specimen (eight years old), perhaps the finest in Scotland, growing in the Caledonian Horticultural Society’s Gardens, Inverleith Row. ... Introduced by Mr. Douglas 

from the west coast of North America in 1828” (protologue); [holotype: not found; a 

specimen with one fascicle of needles marked “ex K in MO,” according to Lauria:18

...was donated to G. Engelmann on the occasion of his visit to Europe in 

1869 and originates from a specimen which, as far as we know today, did 

not serve as holotype to the author of the protologue of the first description 

of Pinus ponderosa. Therefore, this single fascicle does not represent 

type material.

[According to Lauria and the journal of Douglas (1836), specimens (but not a 

type specimen) were collected, 11–12 May 1826, near Spokane (Spokane County), 

Washington. According to Lauria, seeds collected that fall, probably by John 

Work, perhaps in the vicinity of Kettle Falls (Stevens County) or the Pend Oreille 

River (Pend Oreille County), Washington, presumably were given in April 1827 to 

Douglas who returned with them to London. Evidence presented by Lauria leaves 

no doubt as to either proper application of name or nonexistence of a type.]

Absent a type, a neotype is designated here: Washington, Stevens County, Farm 

to Market Road Kelly to Highway 395, at Alex Lewis Place, Barstow Bridge, South 

to Napoleon Railroad Siding, Colville National Forest, about 10 ms south of Orient, 

bench of Kettle River, sandy loam soil, southwest-facing slope, pure ponderosa pine 

stand, approximate latitude 48°46′ N, longitude 118°07’ W, 1,300 to 1,500 ft, T37-

38N, R37E, Sec. 33, 4, 16, WM; 16 Sep 1955, Hugh Cheyney & F.W. Cony, s. n. IFG 

plot 118 (neotype: UC; isoneotypes: A, IFG, K, NA, NEB). Well’s (1964) progeny 

number MSFG 2102 was from the neotype.

• Pinus ponderosa f. crispata F.G. von Schwerin, Mitt. Deutsch. Dendrol. 

Ges. 1919, 325. A sport having sickle-shaped needles. From an unknown 

provenance near Kamloops, British Columbia. Placed in synonymy here on 

basis of geography.

18 Personal communication from Friedrich Lauria, Naturhistorische Museum Wien, 

Vienna, Austria, February 5, 1992.
26

RESEARCH PAPER PSW-RP-264

• Pinus washoensis H. Mason & Stockw., Madroño 8: 61, 1945.—Pinus ponderosa var. washoensis (H. Mason & Stockw.) Ting W.S., Univ. Calif. Publ. 

Geol. Sci. 58:116. 1966 —Pinus ponderosa subsp. washoensis (H. Mason & 

Stockw.) E. Murray, Kalmia 12:23. 1982.—Type: Nevada, Washoe County, 

Mount Rose; 3 mi east of highway summit, south side of Galena Creek; 

elev. 8,100 ft.; 4 August 1940, H.L. Mason, 12,370 (UC, 692993).

This particular neotype for Pinus ponderosa was chosen for three reasons. 

First, it is typical of the ponderosa pine that would have been available to Work, 

the Hudson Bay trader who is believed to have collected the seed that Douglas 

imported to England. Second, it was collected only 12 mi (19 km) north-northwest 

of Work’s headquarters at Kettle Falls, Washington, where Douglas is presumed to 

have received the seeds in April 1827 on his overland return to Hudson Bay. Third, 

it was part (trees in plots 118 and 318) of range-wide collections in 1955 and 1956 of 

ponderosa pine (Callaham 2013) (fig. 2).

The common name, Columbia ponderosa pine, is chosen because most of the 

range of this subspecies is within the watershed of the Columbia River and its 

tributaries. Outside of this watershed, it occurs only in the Fraser River watershed 

in British Columbia, and in southern Oregon. Weidman (1939) called this subspecies “north plateau race,” probably because the geologic area sometimes is called 

the Columbia Plateau. Application of the word “plateau” is deemed inappropriate 

because the geographic area is everything but an elevated, level, tableland. The 

term “Inland Empire,” applied to the area surrounding Spokane, Washington, also 

was rejected because it applies only to a fraction of the range of this subspecies.

Columbia ponderosa pine is characterized by three needles per fascicle (2.97 

to 3.07). Needles from the middle of the annual growth are long, 168 (130 to 205) 

mm. They also are thickest, except for needles of subsp. readiana. Needles have the 

fewest small resin ducts: 0.8 adaxial resin ducts (0.1 to 1.5) plus 2.3 abaxial resin 

ducts (0.1 to 4.1). Hypodermal cell layers in needle corners average 3.4 (2.7 to 3.9). 

Needles remain green an average of 4.7 years (2.2 to 7.6).

Trees display an intermediate number of branches per whorl, 3.7 (1.9 to 5.6). 

Branch angle from vertical in tree tops is relatively flat, 51 (30 to 79) degrees, and 

like that of most other subspecies except readiana.

Color of immature cones during second growing season is dark red to purple on 

the majority of trees but green on occasional trees (Smith 1981). Mature cones (fig. 

3) usually are intermediate in both length, 88.7 mm (72.5 to 103), and width, 71.6 

mm (63.6 to 81.4). The result is a cone of relatively elongate form factor, 0.84 (0.80 

to 1.80).
27

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Seed body is longest for the species, 7.6 mm (6.5 to 8.4). Along with those of 

subsp. critchfieldiana, seeds are widest for the species, 4.9 mm (4.5 to 5.5). Seeds 

are longest in relation to width for the species, form factor 1.57 (1.40 to 1.70). 

Length of seed body plus wing, 24.8 mm (20.2 to 29.5), resembles that of most 

inland subspecies but is much shorter than in Pacific ponderosa pine subsp. critchfieldiana. Length of seed wing alone, 16.6 mm (13.0 to 21.8), also resembles that 

of other inland subspecies but is substantially less than in subsp. critchfieldiana. 

Proportional length of seed wing, as a multiple of seed (body) length, 3.26 (2.90 to 

4.10), is lowest for the species.

Vegetative shoots, before lignification, are green and viscid.19 Buds are reddish 

brown to chestnut brown with loosely appressed scales (Wright et al. 1969).

Monoterpenes in xylem oleoresin of Columbia ponderosa pines are characterized by very high delta-3-carene (48 to 53 percent), less myrcene (19 to 21 percent), 

19 Personal communication from Gerald Rehfeldt, geneticist, USDA Forest Service, 

Intermountain Research Station, Moscow, ID.

Figure 3—One selected cone from each of six trees, neotype of Pinus ponderosa subsp. ponderosa.
28

RESEARCH PAPER PSW-RP-264

and little to very little limonene (7 to 12 percent); resin exuding from xylem is 

colorless to light amber in color (Smith 1977).

Cone Dimorphism

Trees at the location from which the neotype was selected were typical Columbia 

ponderosa pine except for one notable trait—a high proportion of trees produced 

dimorphic cones (fig. 4). Two of four mature, seed-bearing cones collected in 1994 

from a single tree were globose (55 mm wide by 55 mm long, form [width divided 

by length] 1.00), another cone was ovoid (58 mm wide by 64 mm long, form 0.91). 

The fourth cone was elongated (73 mm wide by 87 mm long; form, 0.84). Range 

in length of one long and six short cones from a second tree (in 1994) was 57 to 83 

mm (mean 64.3 mm), and range in form was 0.77 to 0.90 (mean 0.84). But all seven 

cones from a third tree (in 1994) were short, 52 to 65 mm (mean 59.0 mm); their 

form ranged from 0.74 to 0.96 (mean 0.85).

This finding, in 1994, that a tree produced only short cones, caused me to 

reexamine my basic data for the neotype. These data were collected in 1955 from 

five cones from each of 10 (or fewer) trees (Callaham 2013, plot 118). I ascertained 

that one of the 10 trees sampled in 1955 produced only short (67 to 77 mm, ovoid–

globose) cones; seven of those trees produced only longer (88 to 111 mm, elongate–

ovoid) cones; two of those trees produced both short (70 to 73 mm) cones and long 

(97 to 98 mm) cones identical to two of the three trees sampled in 1994. Such an 

allometric shift as this can be under simple genetic control (Gottlieb 1984).

When I first observed dimorphism in cones collected in 1994 from the location 

of the neotype, I thought dimorphic cones were extremely unusual for ponderosa 

pine. That observation led me to reexamine my basic data on cone length for 

Columbia and Pacific ponderosa pines (Callaham 2013). Masked by my original 

calculations of mean cone-length per plot were differences among trees in both 

cone length and cone form that were highly significant statistically. (A negative 

correlation exists between these characters; shorter cones are proportionally wider; 

as cone length decreases cone form increases.) Pronounced cone dimorphism (one 

to several cones 35 to 60 percent longer than the shorter cones) occurred on 16 of 

approximately 570 trees (= 2.6 percent) on 12 of 59 plots (= 20 percent), 1 of 10 

trees on nine plots, 2 of 10 trees on two plots, and 3 of 10 trees on one plot. Pronounced cone dimorphism was an infrequent but not unusual phenomenon in the 

two western subspecies of ponderosa pine.
29

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Figure 4—Cone dimorphism is apparent on two of three pairs of largest and smallest cones from each of three 

trees, neotype of Pinus ponderosa subsp. ponderosa.
30

RESEARCH PAPER PSW-RP-264

Besides the neotype—from a tree located in northeastern Washington—trees 

bearing dimorphic cones were located along the Kootenay River, north of Kimberly, British Columbia (plot 97), at two locations in northern Idaho (plots 106 and 

120), at two locations along the border between Idaho and Montana (plots 109, 182, 

and 183), at two locations in central Oregon (plots 31 and 41), and at three locations 

in the northern Coast Range in California (plots 49, 88, and 195). Dimorphic cones 

also were found on 10 of 17 plots of southwestern ponderosa pine.

Cones shorter than 79 mm and ovoid/globose in shape were collected from 1 to 

9 of 10 trees on most of my 37 plots within the range of Columbia ponderosa pine. I 

was surprised to find that such cones were collected from 1 or 2 of 10 trees (in four 

plots from 3 to 6 of 10 trees) on two-thirds of my 22 plots in the range of Pacific 

ponderosa pine. My conclusions were:

• Individual trees of Columbia ponderosa pines frequently bear small, ovoid/

globose cones that are indistinguishable from cones of Washoe pine.

• Trees of Pacific ponderosa pine bear Washoe-like cones less frequently.

Pinus washoensis versus Columbia ponderosa pine—

Lauria,20 after studying trees in the United Kingdom, concluded that “all cones 

seen from trees documented to originate from Douglas’ introduction are decidedly 

Washoe-like, that means medium to small, dense, egg-shaped/globose and not of 

relatively elongate form ... .” His finding suggests that Douglas’ seed was collected 

from one or more trees (similar to trees 2, 9, 10, and 13 on plot 118) that bore only 

smaller, ovoid–globose cones typically associated with Washoe pine.

My shorter, ovoid–globose cones (figs. 3 and 4) are indistinguishable from 

cones of Washoe pine. Upon reexamining my data from 45 cones collected in 1955 

from nine trees near the type location of that taxon (plot 200 = Wells’ 2292), I found 

that cones ranged in length from 48 to 82 mm, and ranged in form from 0.61 to 1.16. 

Most cones were ovoid to globose, form 0.8 to 1.0. Obviously, the many Columbia 

ponderosa pines that produced smaller cones were indistinguishable from Pinus 

washoensis.

This finding caused me to reexamine the type specimen of Pinus washoensis; 

whereon, I noted an annotation by T.C. Brayshaw, 5 Feb. 1986: “This material does 

not exceed the limits of variability, in any character visible, of Pinus ponderosa

Dougl. ex Laws. var. ponderosa, North Plateau (Columbia) race, as found in British 

Columbia.”

20 See footnote 2.
31

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Remembering admonitions and numerous comments from Lauria,21 I reviewed 

evidences and discussions presented by Haller (1961, 1965a), Critchfield and Allenbaugh (1965), Critchfield and Little (1966), Little (1979), Critchfield (1984), Ting 

(1966), Niebling and Conkle (1990), Smith (1967, 1971, 1977, 1981), Wells (1964), 

and Rehfeldt (1999). Wells (1964a) wrote about Washoe pine: “It was very different 

from all other progenies (of the Pacific ecotype).” Notably, he failed to compare it 

to Columbia ponderosa pine. Haller (1965a) was first to propose that Washoe pine 

be included in the North Plateau race of ponderosa pine. After reexamining my 

data [my plot 200’s 10 trees (= Wells’ 2292) vs. 37 plots (= 370 trees) of Columbia 

ponderosa pine], I concluded Washoe pine and Columbia ponderosa pine do not 

differ significantly in:

• In situ characteristics of size, shape, or immature color of cones, length 

and width of seeds, length of seed wing, or length, width, and anatomy of 

needles

• Monoterpenes in xylem resin

• Many characteristics of seedlings in the nursery.

Using Wells’ data, Critchfield (1984) concluded “Washoe pine was more like 

the North Plateau (Columbia) race...” After examining Wells’ data I concluded there 

were many similarities and only sporadic significant differences between Washoe 

pine and Columbia ponderosa pine.22 Washoe pine (one plot versus seven plots) 

differed significantly in:

• Length of secondary needles (shorter than four plots)

• Susceptibility to winter injury (less than four plots)

• Trees forming terminal buds at age 1 (fewer than five plots)

• Bud scale exsertion (more than five plots)

• Date growth started (later than seven plots)

• Heights at ages 1 or 2 (less than six or seven plots).

All of these significant differences could simply reflect inherent adaptations of 

Washoe pine to grow at a very high elevation (2554 m, 8,300 ft.) and survive in the 

deep, late-melting snowpack of the Sierra Nevada. All of the foregoing evidences 

led me to conclude that Washoe pine and Columbia ponderosa pine are taxonomically synonymous.

21 Lauria, F. 1991, 1992, 1994, 1995. Personal communications. Naturhistorische Museum 

Wien, Vienna, Austria.

22 Washoe pine [my plot 200 (elev. 2554 m) = Wells’ 2292] versus Columbia ponderosa pine 

[my plots 34 (elev. 680 m), 40 (elev. 1540 m), 53 (elev. 1850 m), 100 (elev. 520 m), 102 (elev. 

550 m), 118 (elev. 430 m), 123 (elev. 1290 m) = respectively Wells’ 2032, 2034, 2045, 2124, 

2134, 2102, 2205].
32

RESEARCH PAPER PSW-RP-264

2. Pinus ponderosa Douglas ex C. Lawson subsp. critchfieldiana Callaham 

subsp. nov., Pacific ponderosa pine—

Type: California, Placer County, Forest Hill, northern edge of flat ridge top, about 

50 ft west of northern edge of Forest Hill Ranger Station, Tahoe National Forest, 

approximate latitude 39°01’N, longitude 120°49’W, 3,200 ft, T14N, R10E, Sec. 35, 

MDM, 25 Sep. 1955, Glen E. Sindel s. n. IFG plot 68 (holotype: UC; isotypes: A, 

IFG, K, NA, NEB). Well’s (1964) progeny number MSFG 2056 was from the type.

• Pinus benthamiana Hartweg, J. Hort. Soc. London 2:189. 1847.—Pinus 

ponderosa var. benthamiana (Hartweg) Vasey, Cat. For. Trees, U.S. 

Govt. Print. Office. 30. 1876.—P. ponderosa var. benthamiana (Hartweg) 

Lemmon (1888), comb. superfl.—Type: California, Santa Cruz Co., vicinity 

of Santa Cruz (actually Bonny Doon), 24 Aug 1846, Hartweg s.n. [holotype: not found; John Strother found a specimen in MO, 899036, labeled 

“P. Benthamian (sic) California 1847” that appears to be type material. 

Description and type locality leave no doubt as to application of name.]

• Pinus beardsleyi A. Murray, Edinb. New Phil. J. Ser. 2. 1:286, pl. 6. 1855.—

Pinus ponderosa var. beardsleyi (A. Murray) A. Kellogg, Forest Trees 

Calif., Sacramento, Calif., 44.1882—Type: holotype: not found; specimen 

labeled “Pinus bairdsleyi” by Engelmann, 13 Sept 1869, is in MO;23 text, 

figure, and Engelmann’s specimen leave no doubt as to application of 

this name.

• Pinus craigana A. Murray, Edinb. New Phil. J. Ser. 2. 1:288, pl. 7. 1855.—

Type: holotype: not found; a specimen, perhaps the holotype, labeled 

“ponderosa” by Engelmann, 30 Aug 1869 is in MO, 3574205;24 text, figure, 

and Engelmann’s labeled specimen leave no doubt as to application of this 

name.

• Pinus ponderosa var. nigricans Lemmon, Bull. Calif. State Board For. 7:8. 

1889—Type: holotype: not found; text leaves no doubt as to application of 

this name.

• Pinus ponderosa var. pacifica Haller, Aliso 29(1): 53–57.—Type: in herbarium UCSB, J.R. Haller 10205 (holotype UCSB 69943), leaves no doubt as 

to application of this name.

23 Xerographed copy of specimen provided by Friedrich Lauria, Naturhistorische Museum 

Wien, Vienna, Austria, February 28, 1994.

24 See footnote 2.
33

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Latin description—Differt a P. ponderosa subsp. ponderosa ramis 4.4 (2.7–6.0) 

[vs. 3.7 (1.9 to 5.6)] per verticillum, foliis 198 (144 to 243) mm longis [vs. 168 (130 

to 205)] mm longis, seminum alis 4.34 plo (3.00 to 4.90) [vs. 3.26 plo (2.90 to 

4.10)] seminibus longioribus, strobilis maturescentibus viridis vel luteo-viridis [vs. 

plerumque rubris vel purpureis sed aliquando viridis]. Differt a P. ponderosa subsp. brachyptera viridis foliis retentis 3.9 (1.4 to 6.5) annis [vs. 4.7 (2.2 to 7.6) annis], 

foliifer segmentis ramorum 251 (74 to 521) mm longis [vs. 262 (51 to 846) mm longis], angulis ramorum 56 (30 to 75) gradis [vs. 51 (30 to 79) gradis], foliis 198 (144 

to 243) mm longis [vs. 168 (130 to 205) mm longis], canalibus resiniferis adaxialibus 0.8 (0.2–1.2) [vs. 0.8 (0.1–1.5)] per folium, et stratis cellularum hypodermatum

in angulis foliorum in sectione transversali 3.2 (2.7 to 3.7) [vs. 3.4 (2.7 to 3.9)].

The subspecific name honors Dr. William Burke Critchfield (1923–1989), my 

ever-helpful colleague during 42 years. Together we completed our undergraduate degrees in forestry and doctorates in botany at the University of California 

at Berkeley. Then he served with distinction as botanist at Maria Moors Cabot 

Foundation, Harvard University (1956–1958). He replaced me (1958) as geneticist at 

the IFG at Placerville, California, and continued there until his retirement in 1988. 

As one of only seven Pioneering Research Scientists in the USDA Forest Service, 

his work spanned plant growth and morphology, plant geography, pine hybridization and evolution, and paleobotany. His name is respected around the world for his 

many contributions that clarified taxonomy, geographic distribution, and genetic 

relationships among pines. He substantially added to our understanding of ponderosa pine and of this particular subspecies. In his time, no one knew more about 

pines of the world than he.

Pacific ponderosa pine is chosen as a common name because this subspecies 

grows in three states—California, Oregon, and Washington, all fronting on the 

Pacific Ocean. “Coastal ponderosa pine” (Haller 1965) is not chosen because the 

subspecies grows primarily in interior valleys and mountain ranges. Only rarely 

does it grow in sight of the Pacific Ocean.

Pacific ponderosa pine has these characteristics that distinguish it from other 

subspecies:

• Briefest retention of green needles, 3.9 years (1.4 to 6.5)

• Most branches per whorl, 4.4 (2.7 to 6.0)

• Greatest branch angle from vertical, 56 (30 to 75) degrees

• Longest needles, 198 (144 to 243) mm

• Most uniform display of three needles per fascicle (range 2.99 to 3.04)

• Fewest adaxial resin ducts in needles, 0.8 (0.2 to 1.2)

• Fewest layers of hypodermal cells in needle corners, 3.2 (2.7 to 3.7)
34

RESEARCH PAPER PSW-RP-264

• Longest cones, 101 (64 to 122) mm (fig. 5)

• Widest cones, 77 (56 to 89) mm

• Cones with lowest form factor, 0.80 (0.70 to 1.50)

• Longest seeds, 7.45 (6.9 to 8.1) mm

• Widest seeds (but only very slightly wider than those of subsp. ponderosa)

• Longest seed plus seed wing, 32.3 (24 to 37) mm

• Longest seed wing, 24.8 (16.1 to 28.9) mm

• Greatest proportional length of the seed wing, 4.3 times seed length 

(3.0 to 4.9)

• Seed cones during second summer green to yellow green in color 

(Smith 1981)

Figure 5—One selected cone from each of five trees, type of Pinus ponderosa subsp. critchfieldiana.
35

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

• Pollen cones longest for species, 40 to 90 mm (dried), ranging in color from 

dark red to red purple (Critchfield 1984)

• Highest proportion of beta-pinene in xylem oleoresin (Smith 1977). 

Pacific ponderosa pine differs significantly from Columbia ponderosa 

pine (table 1) by having:

• More branches per whorl

• 18 percent longer needles

• 50 percent longer seed wing

• Greater proportional length of seed wing

• Maturing seed cones green to yellow green vs. usually red to purple 

(occasionally green) during the second summer.

Pacific ponderosa pine differs markedly from Rocky Mountains ponderosa 

pine (table 1) by having:

• Needles retained almost 2 years less

• At least one more branch per whorl and wider branching angle

• Needles that are 75 percent longer but slightly thinner

• No occurrence of two needles per fascicle (confirmed by Read 1980)

• Cones 42 percent longer and tend to be more elongate in form

• Seeds (body) longer by 1 mm, and wider (confirmed by Read 1980)

• Seed wings half again as long

• Seedlings failed to form secondary needles during first year of growth 

(Wells 1964), seedlings of Rocky Mountains ponderosa pine rarely did so

• Foliage color on first-year seedlings during August yellow green to green, 

Rocky Mountains ponderosa pine green to blue- green (Wells 1964)

• Buds reddish brown to chestnut brown with loosely appressed scales 

(Wright et al. 1969).

Pacific ponderosa pine differs significantly from southwestern ponderosa pine 

(table 1) by having:

• Green needles retained almost a half-year less

• Longer needle-bearing segments of branches

• Wider branch angle

• Needles one-third longer

• Only two-thirds as many adaxial resin ducts per needle

• Fewer layers of hypodermal layers in needle corners

• Longer seed body (confirmed by Read 1980) and much longer seed wings

• Seedlings with significantly more cotyledons, attributed to larger seeds by 

Read (1980)
36

RESEARCH PAPER PSW-RP-264

• Fewer secondary needles

• Hardly any seedlings form secondary needles during the first year of 

growth (Wells 1964) , but 45 to 100 percent (depending on seed source) of 

southwestern seedlings formed secondary needles

• Foliage color on first-year seedlings during August yellow green to green 

while that of southwestern ponderosa pine was green to blue green

• Stem color during second year of growth green to light green while southwestern ponderosa pine varied from light green to gray (Wells 1964) 

because of a waxy bloom (Read 1980)

• Current vegetative shoots usually green to brown and viscid or resinous 

to touch, southwestern ponderosa pine shoots usually covered by purplish 

waxy bloom (Read 1980

• Monoterpenes predominantly delta-3-carene (37 to 55 percent) vs. 15 to 42 

percent in southwestern ponderosa pine (Smith 1977)

• Very low amount of alpha-pinene (12 to 29 percent) vs. 38 to 50 percent in 

southwestern ponderosa pine (Smith 1977)

• Oleoresin yellow to dark amber vs. colorless to light amber exuding from 

southwestern ponderosa pine (Smith 1977).

Pacific ponderosa pine differs significantly from central high plains ponderosa pine 

(table 1) by having:

• Only 60 percent of green foliage length on branches

• Four times as many branches per whorl

• Branch angle tending closer to horizontal

• Needles 30 percent longer; more needles per fascicle

• About half as many adaxial needle resin ducts

• Two-thirds as many abaxial needle resin ducts

• Two-thirds as many hypodermal cell layers

• Cones 45 percent longer and 22 percent wider

• Cone form less ovate

• Seed plus wing length 40 percent longer

• Seed wings 50 percent longer

• Hardly any seedlings formed secondary needles during the first year of 

growth vs. 36 to 76 percent (depending on seed source) formed secondary 

needles (Wells 1964), confirmed by Read (1980)
37

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

• Summer foliage color on first-year seedlings (grown in Michigan) yellowgreen to green vs. blue-green (Wells 1964)

• Winter foliage color, when grown in the Great Plains, green vs. purple 

(Read 1980)

• Oleoresin monoterpenes characterized by high amounts of both beta-pinene 

(27 to 45 percent ) and delta-3-carene (35 to 41 percent ) plus considerable 

myrcene (20 to 21 percent ) and limonene (18 to 22 percent ) vs. central 

high plains, not studied by Smith (1977).

3. Pinus ponderosa Douglas ex C. Lawson subsp. scopulorum (Engelm. in 

S. Watson) E. Murray, Kalmia 12:23. (July) 1982, Rocky Mountains (not 

Mountain) ponderosa pine—

Pinus ponderosa var. scopulorum Engelm. in S. Watson, Bot. California 2:126. 

1879 [1880]25—Pinus ponderosa scopulorum (Engelm. in S. Watson) Sudworth, 

U.S. Department of Agriculture Division of Forestry, Bulletin 14: 20. 1897.—Pinus 

scopulorum (Engelm. in S. Watson) Lemmon, Garden and Forest 10:183. 1897.—

Pinus ponderosa subsp. scopulorum (Engelm. in S. Watson) W. A. Weber, 

Phytologia 51: 374. (August) 1982, comb. superfl.

Type: No specimens or locations cited in protologue; referred to in protologue 

only as “P. ponderosa of the Rocky Mountain floras.”—Lauria26 provided a list 

of 19 specimens of Pinus ponderosa var. scopulorum in MO that he attests were 

“studied by Dr. George Engelmann for the publication of the ‘Abietineae’ (1879) in 

‘Botany of California, 1880’.” A search by John Strother (University of California 

Herbarium at Berkeley) through holdings of Pinus ponderosa at the MO herbarium, 

where most of Engelmann’s specimens were deposited, failed to reveal any specimens that were designated or could be construed as type of P. ponderosa var. 

scopulorum.

To fix application of name scopulorum, a neotype is designated here: Pinus 

ponderosa Douglas ex P. Lawson & Lawson subsp. scopulorum (Engelm.) E. Murray, Kalmia 12:23. (July) 1982, Rocky Mountains ponderosa pine—

25 See footnote 2.

26 Same source as footnote 2, personal communication, February 5, 1992.
38

RESEARCH PAPER PSW-RP-264

Neotype: Colorado, El Paso Co., granitic ridge; steep, south-facing 30 to 40 degree 

slope; young, all-aged stand, about 6.5 mi south of Woodland Park Post Office, 

on Railroad Road; up Log Creek to Rampart Range Road, then south to the cattle 

guard; plot sign S. 35° W., 25 links, from SW corner of the concrete on the cattle 

guard; approximate latitude 39°00’N, long. 105°00’W, 9, 100 ft, fall (probably late 

September) 1955, (W.M. Johnson), s. n. IFG plot 21 (neotype: UC; isotypes: A, IFG, 

K, NA, NEB). Well’s (1964) progeny number MSFG 2164 was from the neotype. 

Read’s (1980) collection designated as origin 763 was from vicinity of the neotype.

• Pinus ponderosa pendula H. Sargent, Gard. Chron. 10 (n.s.): 236, f. 42. 

1878, not Pinus pendula Aiton, 1789, a sport having weeping branches from 

an unknown provenance of P. ponderosa fide Sudworth (1897).—Pinus 

ponderosa penduliformis Sudworth, Bull. U.S.D.A. Div. For. 14: 21. 1897, 

nom. superfl., illegit.—Pinus ponderosa f. pendula (H. Sargent) R. A. 

Vines, Trees, Shrubs ... Southwest, Austin, TX. 1960, 19.

• Pinus ponderosa f. nana L. Beissner, Mitt. Deutsch. Dendrol. Ges. 1912, 

365, a sport having a dwarf habit found near Coal Creek, Jefferson Co., 

Colorado by F. von Holdt. Type: unknown; name placed in synonymy here 

on basis of geography.

• Pinus ponderosa f. koolhaas J. L. Mol, Jaarb Ned. Dendrol. Ver. (1952-) 

1953, 74, a sport of dwarf habit having contorted weeping branches. Type: 

unknown; name placed in synonymy here on basis of geography.

Conkle and Critchfield (1988) wrote: “The compact, brushlike, bushy-tuft 

(scopulate) appearance of ponderosa foliage in the Rocky Mountains differed from 

the open, plume-like foliage in western areas, and var. scopulorum was coined in 

recognition of that characteristic ... .”

Obviously they were referring to the Latin adjectives scopulatus or scoparius, 

meaning like a broom or brush. However, Engelmann’s protologue, “of the Rocky 

Mountain flora,” refers to the genitive plural of the Latin noun scopulus (meaning 

of the rock, ledge, shelf, or cliff) and, indirectly, to the Rocky Mountains, often 

shortened to Rockies.

Readers should note my purposeful choice of a new common name, Rocky 

Mountains ponderosa pine. This subspecies grows in the Rocky Mountains, not on 

Rocky Mountain. Would one call the trees growing in the Black Hills, Black Hill 

ponderosa pine? Of course not. So I contend that Rocky Mountains ponderosa pine, 

being the correct common name, should be used henceforth.
39

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Rocky Mountains ponderosa pine has many distinctive, statistically significant 

characteristics: means (ranges):

• Years needles stay green, 5.7 (3.6 to 7.9)

• Branches per whorl, 3.0 (2.0 to 4.6)

• Branching angle, 50 (31 to 76) degrees

• Needle length, 112 (92 to 144) mm

• Needles per fascicle, 2.6 (2.2 to 3.0)

• Hypodermal cell layers, 4.1 (3.6 to 4.4)

• Cone length, 70.7 (52 to 93) mm (fig. 6)

• Cone form factor, 0.90 (0.70 to 1.00)

• Seed (body) length, 6.3 (5.4 to 6.9) mm

• Seed width, 4.1 (3.6 to 4.6) mm

• Seed form, 1.52 (1.4 to 1.6)

• Seed plus wing length, 22.9 (18 to 28) mm

• Seed wing’s absolute length, 16.4 (10 to 21) mm

• Pollen cones yellow, often light pink, occasionally dark red.27

Figure 6—One selected cone from each of seven trees, neotype of Pinus ponderosa subsp. scopulorum.

27 Read, R.A. 1992. Personal communication: “Pollen cones are both yellow and reddish, 

varying tree-to-tree, probably in equal quantities.”
40

RESEARCH PAPER PSW-RP-264

Rocky Mountains ponderosa pine contrasts with Columbia ponderosa pine (table 1) 

by having:

• Needles only two-thirds as long and stiffened by more hypodermal cell layers

• More frequently two rather than three needles per fascicle (confirmed by 

Read 1980)

• Cones ovoid rather than elongate form

• Cone color always green at low to mid elevations, at high elevations (above 

2500 m) sometimes distinctly purple28 as in Columbia ponderosa pine

• Seed plus wing length shorter

• Absolute length of seed wing shorter

• Seeds less elongate and smaller (Read 1980)

• Cotyledons fewer

• Shoots displaying more waxy bloom

• Needles more appressed to stem

• Pollen cones usually yellow (Critchfield 1984), but in Columbia basin dark 

red to red purple (Critchfield 1984)

• Pollen cone color yellow, often light pink, occasionally dark pink to purple 

(Linhart).29

Read (1980), comparing his many seed sources of Rocky Mountains ponderosa pine 

to only one seed source of Pacific ponderosa pine, observed:

• Seeds were small versus large

• Germination was quick versus slow

• Cotyledons were few versus many (which he attributed to differences in 

seed size)

• Winter foliage color on seedlings was purple versus green

• Secondary needles were many versus few

• Needles were appressed versus divergent

• Buds were grayish brown with closely appressed scales (Wright et al. 1969).

Proportions of monoterpenes in xylem oleoresin distinguish Rocky Mountains 

ponderosa pine from other subspecies (Smith 1977). Northern Rocky Mountains 

ponderosa pine growing in central Montana, Wyoming, and South Dakota differs 

significantly from Columbia ponderosa pine growing to the west (more alphapinene, more beta-pinene, less delta-3-carene, and less myrcene). Western Rocky 

Mountains ponderosa pine growing in Utah and Nevada differs significantly from 

Columbia ponderosa pine growing to the north (more alpha-pinene, less delta-3-

28 Linhart, Y.B. 1998. Professor, University of Colorado, Boulder, CO.

29 See footnote 2.
41

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

carene, and less myrcene). Rocky Mountains ponderosa pine differs from Pacific 

ponderosa pine by having less beta-pinene, more delta-3-carene, less myrcene, and 

less limonene. It differs from southwestern ponderosa pine by having less alphapinene, more beta-pinene, more delta-3-carene, and more myrcene.

4. Pinus ponderosa Douglas ex C. Lawson subsp. readiana Callaham, subsp.

nov., central high plains ponderosa pine—

Type: Nebraska, Keya Paha Co., south aspect of canyons and breaks sloping from 

tableland to Niobrara River valley, ca. 1.7 mi northwest of Niobrara River bridge at 

Carnes P.O., 11 mi. north, 1 mi east of Bassett, approx. lat. 42°45’N, long. 99°32’W, 

2,100 ft, 5 Oct. 1955, R. A. Read s. n. IFG plot 23 (holotype: UC; isotypes: A, IFG, 

K, NA, NEB). Well’s (1964) progeny number MSFG 2180 was from the type. 

Latin description—Differt a P. ponderosa subsp. scopulorum ramis 1.3 (1.1to 1.6) 

[vs. 3.0 (2.0 to 4.6) per verticillum, foliiferis segmentis ramorum 422 (259 to 650) 

mm longis [vs. 211 (114 to 429) mm], foliis 156 (148 to 179) mm longis [vs. 112 (92 

to 144) mm], canalibus resiniferis abaxialibus 3.9 (2.1 to 5.6) [vs. 2.4 (1.5 to 3.9) 

per folium, canalibus resiniferis adaxialibus 1.5 (0.6–2.6) [vs. 0.9 (0.3 to 2.5)] per

folium, and seminum alis 16.1 (14.3–17.7) mm longis [vs. 16.4 (10.0–21.1) mm].

The subspecific name honors Ralph A. Read (1916–2001) who served with 

distinction until his retirement in 1979 as a research forester and geneticist at the 

USDA Forest Service’s Shelterbelt (now Agroforestry) Laboratory in Lincoln, 

Nebraska. His postgraduate studies were at Yale University, School of Forestry 

(MF, 1949) and at the University of Nebraska in botany and genetics (1960–1961). 

His definitive research substantially added to our understanding of patterns of 

inherent variation in ponderosa pines growing in the High Plains and the Rocky 

Mountains. He was the authority on the variability and ecology of ponderosa pine 

growing east of the Continental Divide.

The common name recognizes occurrence of P. ponderosa subsp. readiana in 

the central High Plains but not in either the northern or southern high plains, where 

subsp. scopulorum prevails.

The sparse, upright branching habit of this subspecies is unique. It has fewest 

branches per whorl of any subspecies, 1.3 (1.1 to 1.6), and narrowest branching 

angle, 36 (31 to 40) degrees. Green needles extend much farther along the branch 

than in any other subspecies, 422 mm (259 to 650), making branches look like the 

long tail of a fox. Needles are widest for the species and have thickest layers of 

hypodermal cells, 4.7 (4.5 to 4.9), making them very stiff. Needles have greatest 

number of small resin ducts—adaxial ducts, 1.5 (0.6 to 2.6) and abaxial ducts, 3.9 
42

RESEARCH PAPER PSW-RP-264

(2.1 to 5.6) (confirmed by Deneke and Funsch 1972). This subspecies has fewest 

needles per fascicle, 2.4 (2.2 to 2.8) (not confirmed by Read 1980, studying 3-yearold seedlings).

Mature cones are ovoid to globose and have a form factor of 0.90 (0.8 to 1.0) 

(fig. 7). Proportional length of seed wing, as a multiple of seed length, is almost 

lowest for the species, 3.3 (3.2 to 3.5). Critchfield (1984) reported that pollen cones 

are red or purple.

Central High Plains ponderosa pine grows on breaks of the White, Niobrara, 

and Platte Rivers in western Nebraska and adjacent portions of South Dakota, 

Wyoming, and Colorado. It can be distinguished from adjacent Rocky Mountains 

ponderosa pine by several characteristics. Most notable about central plains ponderosa pine are foxtail-like foliage, extending almost twice as far along shoots; 

upright branching habit; fewer branches per whorl; 40-percent longer needles, much 

less appressed to the branch; more resin ducts in each needle; and more layers of 

hypoderm in corners of needles.

Read (1980) noted that needles on 3-year-old seedlings from his particular plots, 

that I would refer to subsp. readiana, were much longer (confirming my finding) 

Figure 7—One selected cone from each of six trees, type of Pinus ponderosa subsp. readiana.
43

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

and much less appressed to stem than were those on seedlings of subsp. scopulorum. He also found that 3-year-old seedlings of subsp. readiana were taller and 

heavier than comparable seedlings of subsp. scopulorum. My examination of data 

published by Wells (1964) and Wright et al. (1969), for trees grown in Michigan, did 

not disclose any significant differences between the two subspecies.

5. Pinus ponderosa Douglas ex C. Lawson subsp. brachyptera (Engelm. in 

Wislizenus), comb. nov., southwestern ponderosa pine—

Pinus brachyptera Engelm. in Wislizenus, Mem. Tour No. Mex., Senate Misc. Publ. 

26, 30th U.S. Congr. 89. 1848.30—Pinus ponderosa var. brachyptera (Engelm. in 

Wislizenus) Lemmon, Second Biennial Rpt. Calif. State Board For. 73, 98. 1888.—

Type: “ ... beginning about Rock creek31 (sic) to Santa Fe” (specimen label; a 

highway distance of 63 miles, 101 km), “Mountains of New Mexico” (protologue); 

from journal by Wislizenus, I determined the type locality to be in San Miguel 

County, along Gallinas Creek, south of Las Vegas toward Romeroville, (probably 

T15N, R16E, NMB,32 at 8,000 ft elev., approximate latitude 35°40’ N, longitude 

105°28’ W) reported on 25 June 1846, specimen label dated 5 July 1846 (when 

the collector was in Santa Fe). Dr. A. Wislizenus s n. 534 (type: MO 1817026-27). 

Read’s (1980) plot 864 is from this type locality.

This taxon, when originally described by Engelmann, was not given a common 

name. Lemmon (1889, 1890) called it southern yellow pine, a name subsequently 

confused with common names for other pines in southeastern United States. I 

believe Critchfield (1984) was first to apply the name southwestern ponderosa 

pine to this taxon. Peloquin (1984), following Critchfield’s lead, also used this 

common name.

Southwestern ponderosa pine is distinguished from all others by having the 

thinnest needles; a seed (body) that is widest in relation to length, seed form factor 

1.48 (1.30 to 1.60); and shortest absolute length of seed wing, 15.5 mm (15.1to 19.3). 

This last feature caused Engelmann to call it brachyptera, “short-winged.” Subsequently, Lemmon (1888) erred when he wrote “This pine was so named by Dr. 

Engelmann, from a mistaken impression that the seed-wings were very short.”

Another distinguishing feature of southwestern ponderosa pine, overlooked in 

the study by Callaham (2013), is the waxy bloom covering current shoots of many 

30 Xerographed copy of type specimen provided as in footnote 23.

31 J. Richard Salazar, Chief, Archival Services, State Records, Santa Fe, New Mexico, in a 

March 8, 1995, conversation, said there is no “Rock Creek” in either San Miguel County or 

Santa Fe County. He cited his authority as Pearce (1965). Perhaps Wislizenus applied the 

name “Rock Creek” to the Gallinas River. Its bed is close to Romeroville where on June 25, 

1846, he first described this pine in his journal.

32 Same source as footnote 28, personal communication, August 21, 1991.
44

RESEARCH PAPER PSW-RP-264

seedlings and trees. Its color has been described variously as “purple,” “gray,” or 

“white” (Read 1980, Weidman 1939, Wells 1964, Wright et al. 1969). A very high 

proportion of specimens from this subspecies, examined in the IFG herbarium in 

Placerville, California, had a whitish purple bloom on current shoots.

Other important characteristics that distinguish southwestern ponderosa 

pine are:

• Years needles stay green, 4.3 (2.5 to 5.9)

• Foliage length, 218 (66 to 538) mm

• Branches per whorl, 3.4 (1.6 to 6.6)

• Branch angle, 48 (30 to 79) degrees

• Needle length, 147 (112 to 198) mm

• Needles per fascicle, 3.0 (2.7 to 3.5)

• Hypodermal cell layers, 4.1 (3.4 to 4.5)

• Adaxial resin ducts per needle, 1.2 (0.7 to 2.4)

• Cone form, 0.86 (0.80 to 1.00)

• Seed plus wing length, 23.3 (18.2 to 26.2) mm.

Buds are grayish brown with closely appressed scales (Wright et al. 1969).

Monoterpenes in xylem oleoresin include a low but variable proportion of 

delta-3-carene (15 to 42 percent) and a moderate to high proportion of amount of 

alpha-pinene (38 to 50 percent); color of oleoresin exuding from xylem “is colorless 

to light amber” (Smith 1977).

Southwestern ponderosa pine differs significantly from adjacent Rocky Mountains ponderosa pine (table 1) by more consistently having three needles per fascicle 

(confirmed by Read 1980). Its needles are slightly narrower but 30 percent longer 

(confirmed by Read 1980). Its seeds are less elongate. Seed wings are nearly a millimeter shorter. Read (1980) also showed that its seedlings:

• Started growth much later

• Grew both faster and larger

• Had longer needles and needle sheaths

• Had divergent needles (that is, were less appressed)

• Tended to have shoots covered by a waxy bloom [confirmed by Wright et al. 

(1969)].

Smith (1977) showed that monoterpenes differ significantly with southwestern 

ponderosa pine having a relatively low proportion of delta-3-carene (15 to 42 vs. 

37 to 55 percent) and a very high proportion of alpha-pinene (38 to 50 vs. 12 to 29

percent).

Significant differences from Pacific ponderosa pine were discussed previously 

under the section where that subspecies was described.
45

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Acknowledgments

This paper was written and revised after consultations with Lawrence Heckard, 

then Curator of the Jepson Herbarium at the University of California at Berkeley, 

and John Strother, University Herbarium of the University of California at Berkeley. 

I am deeply indebted to them for the guidance and technical support they generously provided. Special appreciation is expressed to Dr. Strother for providing Latin 

diagnoses for new subspecies, examining specimens held in other herbaria, preparing and distributing to herbaria the specimens for new taxa, providing guidance 

on dealing with taxonomic difficulties, and contributing to improvements in the 

manuscript. 

Friedrich Lauria, Department of Botany, Natural History Museum, Vienna, 

Austria—the world’s leading authority on ponderosa pine—generously provided 

helpful comments on the manuscript, drafts of his publications in progress, his 

“Index to Nomenclature (Synonymy) of Pinus ponderosa and its Complex,” findings from his studies in the United Kingdom, and reprints from what must be the 

most comprehensive collection of documents pertaining to taxonomy of ponderosa 

pine and related species.

This study was made possible, in part, by a grant from the Forest Genetics 

Research Foundation to the Institute of Forest Genetics, USDA Forest Service, 

Placerville, California.

Metric Equivalents

When you know: Multiply by: To find:

Feet (ft) 0.305 Meters 

Miles (mi) 1.609 Kilometers
46

RESEARCH PAPER PSW-RP-264

Literature Cited

Brayshaw, T.C. 1997. Washoe and ponderosa pines on Promontory Hill near 

Merritt, B.C., Canada. Wien, Austria: Annalen des Naturhistorischen Museums 

in Wien. 99B: 673–680.

Callaham, R.Z.; Liddicoet, A.R. 1961. Altitudinal variation at 20 years in 

ponderosa and Jeffrey pines. Journal of Forestry. 59(11): 814–820.

Callaham, R.Z. 2013. Pinus ponderosa: Geographic races and subspecies based on 

morphological variation. Res. Pap. PSW-RP-265. Albany, CA: U.S. Department 

of Agriculture, Forest Service, Pacific Southwest Research Station. 53 p. 

Conkle, M.T. 1973. Growth data for 29 years from the California elevational 

transect study of ponderosa pine. Forest Science. 19(1): 31–39.

Conkle, M.T.; Critchfield, W.B. 1988. Genetic variation and hybridization 

of ponderosa pine. In: Baumgartner, D.M.; Lotan, J.E., eds. Proceedings, 

Symposium on ponderosa pine—the species and its management, Spokane, 

Washington, 27–43.

Coues, E. 1893. History of the expedition under the command of Lewis and Clark, 

Volume 1. New York: Francis P. Harper. 352 p.

Critchfield, W.B. 1984. Crossability and relationships of Washoe pine. Madroño. 

31: 144–170.

Critchfield, W.B.; Allenbaugh, G.L. 1965. Washoe pine on the Bald Mountain 

Range, California. Madroño. 18: 63–64.

Critchfield, W.B.; Little, E.L. , Jr. 1966. Geographic distribution of the pines of 

the world. Misc. Pub. 991. Washington, DC: U.S. Department of Agriculture, 

Forest Service. 97 p.

Deneke, F.; Funsch, R.W. 1972. Resin canal number varies in ponderosa pine 

(Pinus ponderosa Laws.). Silvae Genetica. 21: 252.

Douglas, D. 1827. An account of a new species of Pinus, native of California: in 

a letter to Joseph Sabine, Esq., F.R. and L.S., Secretary of the Horticultural 

Society. Transactions of the Linnean Society of London. 15: 497–500.

Douglas, D. 1836. A sketch of a journey to the north-western parts of the continent 

of North America, during the years 1824, 5, 6, and 7. Comp. Bot. Mag. 2: 82–140.

Douglas, D. 1914. Journal kept by David Douglas during his travels in North 

America, 1823–1827. London: William Wesley and Son. 364 p.
47

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Duffield, J.W. 1952. Relationships and species hybridization in the genus Pinus. Z. 

Forstg. u. Forstpflanzenz. Silvae Genetica. 1: 93–100.

Duffield, J.W.; Cumming, W.C. 1949. Does Pinus ponderosa occur in Baja 

California? Madroño. 10: 22–24.

Engelmann, G. 1848. Botanical appendix. In: Wislizenus, A., ed., Memoir of a 

tour to northern Mexico, connected with Col. Doniphan’s expedition, in 1846 and 

1847. Misc. Doc. 26. Washington, DC, 30th Congress, United States Senate: 89.

Engelmann, G. 1878. Coniferae. In: Report upon United States geographical 

surveys west of the one hundredth meridian, in charge of First Lieut. Geo. M. 

Wheeler. Vol. 6 Botany. Washington, DC: Government Printing Office.

Engelmann, G. 1879 [1880]. Tribe III. Abietineae. In: Watson, Sereno (ed.) 

Geological survey of California, botany. Cambridge, MA: University Press, John 

Wilson and Son. 2: 125–126.

Gordon, G. 1858. The pinetum: being a synopsis of all the coniferous plants at 

present known, with descriptions, history, and synonymies, and comprising 

nearly one hundred new kinds. Third issue, with additions. London: Henry G. 

Bohn: 202–203.

Gordon, G. 1862. A supplement to Gordon’s pinetum: containing descriptions and 

additional synonymes of all the coniferous plants not before enumerated in that 

work with corrections up to the present time. London: Henry G. Bohn: 67.

Gottlieb, L. D. 1984. Genetic and morphological evolution in plants. American 

Naturalist. 123(5): 681–709.

Haller, J.R. 1961. Some recent observations on ponderosa, Jeffrey, and Washoe 

pines in northeastern California. Madroño. 16: 126–132.

Haller, J.R. 1962. Variation and hybridization in ponderosa and Jeffrey pine. 

University of California Publications in Botany. 34(2): 123–166.

Haller, J.R. 1965a. Pinus washoensis in Oregon: taxonomic and evolutionary 

implications. American Journal of Botany. 52: 646 (abst.).

Haller, J.R. 1965b. The role of 2-needle fascicles in the adaptation and evolution of 

ponderosa pine. Brittonia. 17(4): 354–382.

Haller, J.R.; Vivrette, N.J. 2011. Ponderosa pine revisited. Aliso. 29(1): 53–57.

Hartweg, T. 1847. Journal of a mission to California in search of plants. Part III. 

Journal of the Horticultural Society of London. 2: 187–191.
48

RESEARCH PAPER PSW-RP-264

Hartweg, T. 1848. Journal of a mission to California in search of plants. Part IV. 

Journal of the Horticultural Society of London. 3: 217–228.

James, E.P. 1823. Account of an expedition from Pittsburgh to the Rocky 

Mountains, performed in the years 1819 and ‘20, by order of the Hon. J. C. 

Calhoun, Sec’y of War; under the command of Major Stephen H. Long. From 

the notes of Major Long, Mr. T. Say, and other gentlemen of the exploring 

party. Compiled by Edwin James, botanist and geologist for the expedition. 

Philadelphia, PA: American Philatelic Society. 2 vol., Atlas.

James, E.P. 1825. Catalogue of plants collected during a journey to and from the 

Rocky Mountains, during the summer of 1820. Philadelphia, PA: Transactions of 

the American Philosophical Society, New Series. 2(8): 172–190.

Kempff, G. 1928. Non-indigenous western yellow pine plantations in northern 

Idaho. Northwest Science. 2(2): 54–58.

LaFarge, T. 1974. Genetic differences in stem form of ponderosa pine grown in 

Michigan. Silvae Genetica. 23: 211–213.

Larson, M.M. 1967. Effect of temperature on initial development of ponderosa 

pine seedlings from three sources. Forest Science. 13(3): 286–294.

Lauria, F. 1991. Taxonomy, systematics, and phylogeny of Pinus, subsection 

Ponderosae Loudon (Pinaceae). Alternative concepts. Linzer Biologische 

Beitraege. 23(1): 129–202.

Lauria, F. 1996. The identity of Pinus ponderosa Douglas ex C Lawson (Pinaceae). 

Linzer Biologische Beitraege. 28(2): 999–1052.

Lauria, F. 1997. The taxonomic status of Pinus washoensis H. Mason & Stockw. 

(Pinaceae). Annalen des Naturhistorischen Museums in Wien. 99B: 655–671.

Lawson, C. (P. Lawson and Son.) 1836. The agriculturist’s manual: being a 

familiar description of the agricultural plants cultivated in Europe. Edinburgh, 

United Kingdom: William Blackwood and Sons, 430 p. 

Lemmon, J.G. 1888. Pines of the Pacific slope. In: Second biennial report of the 

California State Board of Forestry for the years 1887–1888. Sacramento, CA: 

State Board of Forestry: 73: 97–99.

Lemmon, J.G. 1889. Supplement to forestry report for 1887 and 1888—Botanist’s 

Department. Revision of broken-cone pines. Sacramento, CA: California State 

Board of Forestry Bul. 7: 6–11. 
49

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Lemmon, J.G. 1890. Revision of broken-cone pines. In: Third Biennial Report, 

California State Board of Forestry for the years 1889–1890. Sacramento, CA: 

California State Board of Forestry: 196–201.

Lemmon, J.G. 1893. Notes on west American Coniferae.–II. Erythia. 1: 134–136.

Lemmon, J.G. 1895. Handbook of west–American conebearers. 3rd ed. Privately 

published, Oakland, CA. p. 35.

Lemmon, J.G. 1897. Three west-American conifers. Garden and Forest. 10: 183.

Lemmon, J.G. 1900. Handbook of west–American conebearers. 4th (pocket) ed. 

Privately published, Oakland, CA.

Linhart, Y.B.; Grant, M.C.; Montazer, P. 1989. Experimental studies in 

ponderosa pine. I. Relationship between variation in proteins and morphology. 

American Journal of Botany. 76(7): 1024–1032.

Little, E.L., Jr. 1971. Atlas of United States trees. Vol. 1. Conifers and important 

hardwoods. Misc. Pub. 1146. Washington, DC: U.S. Department of Agriculture, 

Forest Service. 200 p.

Little, E.L., Jr. 1979. Checklist of United States trees (native and naturalized.) 

Agric. Handb. 541. Washington, DC: U.S. Department of Agriculture, Forest 

Service. 375 p.

Little, E.L., Jr.; Critchfield, W.B. 1969. Subdivisions of the genus Pinus (pines). 

Misc. Pub. 1144. Washington, DC: U.S. Department of Agriculture, Forest 

Service. 51 p.

Loudon, J.C. 1830. Hortus Britannicus. London: Longman, Rees, Orme, Brown 

and Green. 576 p.

Manetti, J. 1844. Catalogi plantarum, caesarei regii horti, prope modiciam, 

supplementum primum. Mediolani. 28 p.

Mason, H.L.; Stockwell, P. 1945. A new pine from Mount Rose, Nevada. 

Madroño. 8(2): 61–63. 

McKelvey, S.D. 1955. Botanical exploration of the trans-Mississippi west, 1790–

1850. Jamaica Plains, MA: Arnold Arboretum of Harvard University: 957.

Mirov, N.T. 1929. Chemical analysis of the oleoresins as a means of distinguishing 

Jeffrey pine and western yellow pine. Journal of Forestry. 27: 176–187.

Mirov, N.T. 1961. Composition of gum turpentines of pines. Tech. Bull. 1239. 

Washington, DC: U.S. Department of Agriculture. 158 p.
50

RESEARCH PAPER PSW-RP-264

Moore, M.B.; Kidd, F.A. 1982. Seed source variation in induced moisture stress 

germination of ponderosa pine. Tree Planters’ Notes. 33(l): 12–14.

Murray, A. 1855. Description of new coniferous trees from California. Edinburgh 

New Philosophical Journal. Series 2. 1: 284–295.

Murray, E. 1982. Notae Spermatophytae. Kalmia. 12: 23. July.

Niebling, C.R.; Conkle, M.T. 1990. Diversity of Washoe pine and comparisons 

with allozymes of ponderosa pine races. Canadian Journal of Forest Research. 

20: 298–308.

Pearce, T.M. 1965. New Mexico place names. Albuquerque, NM: University of 

New Mexico Press.

Peloquin, R.L. 1984. The identification of three-species hybrids in the ponderosa 

pine complex. The Southwestern Naturalist. 29(1): 115–122.

Perry, J.P., Jr. 1991. The pines of Mexico and Central America. Portland, OR: 

Timber Press. 231 p. 

Read, R.A. 1980. Genetic variation in seedling progeny of ponderosa pine 

provenances. Forest Science. Monograph 23. 59 p.

Read, R.A. 1983. Ten-year performance of ponderosa pine provenances in the 

Great Plains of North America. Res. Pap. RM-RP-250. Fort Collins, CO: U.S. 

Department of Agriculture, Forest Service, Rocky Mountain Forest and Range 

Experiment Station. 17 p.

Read. R.A.; Sprackling, J.A.. 1981. Hail damage variation by seed source in 

a ponderosa pine plantation. Res. Note RM-RN-410. Fort Collins, CO: U.S. 

Department of Agriculture, Forest Service, Rocky Mountain Forest and Range 

Experiment Station. 6 p.

Rehfeldt, G.E. 1986a. Adaptive variation in Pinus ponderosa from Intermountain 

regions. I. Middle Columbia River system. Res. Pap. INT-RP-373. Ogden, UT: 

U.S. Department of Agriculture, Forest Service, Intermountain Research 

Station. 9 p.

Rehfeldt, G.E. 1986b. Adaptive variation in Pinus ponderosa from Intermountain 

regions. II. Snake and Salmon River basins. Forest Science. 32: 79–92.

Rehfeldt, G.E. 1990. Genetic differentiation among populations of Pinus 

ponderosa from the upper Colorado River basin. Botanical Gazette. 

151: 125–137.
51

Pinus ponderosa: A Taxonomic Review With Five Subspecies in the United States

Rehfeldt, G.E. 1991. Models of genetic variation for Pinus ponderosa in the inland 

Northwest (U.S.A.). Canadian Journal of Forest Research. 21: 1491–1500.

Rehfeldt, G.E. 1993. Genetic variation in the Ponderosae of the Southwest. 

American Journal of Botany. 80: 330–343.

Rehfeldt, G.E.; Wilson, B.C.;Wilson, S.P.; Jeffers, R.M. 1996. Phytogeographic, 

taxonomic, and genetic implications of phenotypic variation in the Ponderosae of 

the Southwest. The Southwestern Naturalist. 41(4): 409–418.

Rehfeldt, G.E. 1999a. Systematics and genetic structure of Washoe pine: 

Applications to conservation genetics. Silvae Genetica 48(3–4): 167–173. 

Rehfeldt, G.E. 1999b. Systematics and genetic structure of Ponderosae taxa 

(Pinaceae) inhabiting the mountain islands of the Southwest. American Journal 

of Botany. 86: 741–752.

Righter, F.I.; Duffield, J.W. 1951. Interspecies hybrids in pines. Journal of 

Heredity. 42: 75–80. 

Sargent, C.S. 1889. Notes upon some North American trees. Garden and Forest. 

2: 496.

Sargent, C.S. 1897. The first account of some western trees. Garden and Forest. 10: 

28, 29, 38–40.

Sargent, C. 1898. The silva of North America. Vol. 8. Coniferae. Boston and New 

York: Houghton, Mifflin and Co . p. 77–82. Reprinted in 7 vol., Vol. 7. Coniferae. 

1947. New York: Peter Smith. 

Shaw, G.R. 1909. The pines of Mexico. Publications of the Arnold Arboretum 1. 

Jamaica Plains, MA: Arnold Arboretum of Harvard University. 29 p.

Shaw, G.R. 1914. The genus Pinus. Publications of the Arnold Arboretum 5. 

Cambridge, MA: Riverside Press. 96 p.

Silba, J. 1990. A supplement to the international census of the Coniferae, II. 

Phytologia. 68(1): 59.

Smith, R.H. 1967. Variations in the monoterpene composition of the wood resin of 

Jeffrey, Washoe, Coulter and lodgepole pines. Forest Science. 13: 246–252.

Smith, R.H. 1971. Xylem monoterpenes of Pinus ponderosa, P. washoensis, and P.

jeffreyi in the Warner Mountains of California. Madroño. 21: 26–32.
52

RESEARCH PAPER PSW-RP-264

Smith, R.H. 1977. Monoterpenes of ponderosa pine xylem resin in western United 

States. Tech. Bul. 1532. Washington, DC: U.S. Department of Agriculture, Forest 

Service. 48 p.

Sorenson, F.C., Mandel, N.L.; Aagaard, J.E. 2001. Role of selection versus 

historical isolation in racial differentiation of ponderosa pine in southern Oregon: 

an investigation of alternative hypotheses. Canadian Journal of Forest Research. 

31: 1127–1139.

Sudworth, G.B. 1897. Nomenclature of the arborescent flora of the United States. 

Bulletin 14. Washington, DC: U.S. Department of Agriculture, Division of 

Forestry. 419 p. 

Ting, W.S. 1966. Determination of Pinus species by pollen statistics. University of 

California Publications in Geological Sciences. 58: 116.

Torrey, J. 1828. Some account of a collection of plants made during a journey to 

and from the Rocky Mountains in the summer of 1820, by Edwin P. James, M.D., 

Assistant Surgeon, U.S. Army. New York: Annals of the Lyceum of Natural 

History of New York. 2: 161–254.

Van Haverbake, D.F. 1988. Genetic variation in ponderosa pine: a 15-year test of 

provenances in the Great Plains. Res. Pap. RM-RP-265. Fort Collins, CO: U.S. 

Department of Agriculture, Forest Service, Rocky Mountain Forest and Range 

Experiment Station. 16 p.

Vasey, G. 1876. Catalog of the forest trees of the United States. Washington, DC: 

Government Printing Office. 38 p.

Wang, Chi-Wu. 1977. Genetics of ponderosa pine. Res. Pap. WO–34. Washington, 

DC: U.S. Department of Agriculture, Forest Service. 24 p.

Wells, O.O. 1964. Geographic variation in ponderosa pine. I. The ecotypes and 

their distribution. Silvae Genetica. 13(4): 89–103.

Weidman, R.H. 1939. Evidences of racial influence in a 25-year test of ponderosa 

pine. Journal of Agricultural Research. 59(12): 855–887.

Wislizenus, A. 1848. Memoir of a tour to northern Mexico connected with Col. 

Doniphan’s expedition, in 1846 and 1847. Senate Misc. Doc. 26. Washington, 

DC: 30th Session. 

Wright, J.W.; Lemmien, W.A.; Bright, J.N. 1969. Early growth of ponderosa pine 

ecotypes in Michigan. Forest Science. 15(2): 121–129.
This publication is available online at www.fs.fed.us/psw/. You may also order additional 

copies of it by sending your mailing information in label form through one of the following 

means. Please specify the publication title and series number.

Fort Collins Service Center 

Web site http://www.fs.fed.us/psw/

Telephone (970) 498-1392

FAX (970) 498-1122

E-mail rschneider@fs.fed.us

Mailing address Publications Distribution

Rocky Mountain Research Station

240 West Prospect Road

Fort Collins, CO 80526-2098

Pacific Southwest Research Station

800 Buchanan Street

Albany, CA 94710