Pseudotsuga menziesii



The Basics

Taxonomy: Kingdom - Plantae (plants). Subkingdom - Tracheobionta (vascular plants). Superdivision - Spermatophyta (seed plants). Division - Coniferophyta (conifers). Class - Pinopsida. Order - Pinales. Family - Pinaceae (pine). Genus - Pseudotsuga Carrière. Species - Pseudotsuga menziesii (Mirb.) Franco

Pseudotsuga menziesii has two widely recognized varieties: Pseudotsuga menziesii var. menziesii (Mirb.) Franco, coast Douglas-fir or the "green" variety, is found west of the Sierra Nevada and Cascade Mountains. Pseudotsuga menziesii var. glauca (Beissn.) Franco, Rocky Mountain Douglas-fir or the "blue" variety, is native to the Rocky Mountains and interior mountains of the Pacific Northwest.

Ecology: The latitudinal range of Douglas-fir is the greatest of any commercial conifer of western North America. Wherever Douglas-fir grows in mixture with other species, the proportion may vary greatly, depending on aspect, elevation, kind of soil, and the past history of an area, especially as it relates to fire. This is particularly true of the mixed conifer stands in the southern Rocky Mountains where Douglas-fir is associated with ponderosa pine, southwestern white pine (Pinus strobiformis), corkbark fir (Abies lasiocarpa var arizonica), white fir (Abies concolor), blue spruce (Picea pungens), Engelmann spruce (Picea engelmannii), and aspen (Populus tremuloides). Coast Douglas-fir is a major, long-lived seral dominant of low and middle elevation moist forests from southwestern British Columbia to northwestern California. In these forests it is shade intolerant and requires stand-destroying disturbance (wildfire, logging, extensive windthrow) to initiate a new cohort of seedlings. Rocky Mountain Douglas-fir is a shade-tolerant climax species in dry to moist lower and middle elevation forests but is relatively shade intolerant in wetter forests. In the absence of disturbance it tends to replace interior ponderosa pine, Rocky Mountain lodgepole pine, and western larch in the northern Rockies

Pseudotsuga menziesii is found in all three of the Western Forest Initiative 'big plots'. It is abundant in the Wind River Forest Dynamics Plot, and is the second most abundant species by basal area. It is uncommon in the Yosemite Forest Dynamics Plot, and all but one large individual were killed in the 2013 fire. In the Utah Forest Dynamics Plot, it is found in low abundance on north-facing slopes.


Coast Douglas-fir is a large, coniferous, evergreen tree. Adapted to a moist, mild climate, it grows bigger and more rapidly than the inland variety. Trees 5 to 6 feet (150-180 cm) in diameter (150-180 cm) and 250 feet (76 m) or more in height are common in old-growth stands. These trees commonly live more than 500 years and occasionally more than 1,000 years. Old individuals typically have a narrow, cylindric crown beginning 65 to 130 feet (20-40 m) above a branch-free bole. Self-pruning is generally slow and trees retain their lower limbs for a long period. Young, open-grown trees typically have branches near the ground. It often takes 77 years for the bole to be clear to a height of 17 feet (5 m) and 107 years to be clear to a height of 33 feet (10 m). In wet coastal forests, nearly every surface of old-growth coast Douglas-fir is covered by epiphytic mosses and lichens.


Anthropogenic disturbance: Past (and to an extent) present logging has had huge negative impacts on ‘old growth’ forests dominated by Douglas-fir. This is a threat to the ecosystem peculiar to old growth conifer forests, and its biodiversity, in the region. It is not a threat to the survival of the species Douglas-fir, which in most circumstances has regenerated and will regenerate after logging. It is important to separate these issues, and this assessment is concerned with the threat to extinction of a species, not with the threat to an ecosystem unless that impinges on the survival chances of the species concerned.

Fire effects: Crown fires, when they occur, destroy stands of all ages. The thick bark of older Douglas-firs, however, makes them fairly resistant to ground fires. Thick, corky bark on the lower bole and roots protects the cambium from heat damage. In addition, the tall trees have their foliage concentrated on the upper bole, which makes it difficult for fire to reach the crown. Temperatures in excess of 60 C are lethal to Douglas-fir seeds. Thus most seeds on the forest floor will be destroyed by fire. Crown fires will kill seeds in green cones; however, green cones are relatively good insulators and are not highly flammable, and fires that not excessively hot often only scorch the cones. Seeds can mature in scorched cones on fire-killed trees, and later disperse onto the burned area.

Pests and pathogens: Douglas-fir is host to dwarf mistletoe, Arceuthobium douglasii. A variety of native pathogens will infect Douglas-fir, including Armillaria solidipes, Phellinus weirii, and Phaeolus schweinitzii. The primary insect pest of Douglas-fir is Dendroctonus pseudotsugae.

Other: High winds following heavy rains occasionally cause heavy losses from blowdown in the Pacific Northwest. Heavy snow and ice storms periodically break the tops of scattered trees in dense young stands. Consumption of Douglas-fir seeds by small forest mammals such as white-footed deer mice, creeping voles, chipmunks, and shrews, and birds such as juncos, varied thrush, blue and ruffed grouse, and song sparrows further reduces seed quantity. A single deer mouse may devour 350 Douglas-fir seeds in a single night.


Seed production - Douglas-fir is monoecious; trees commonly begin to produce strobili at 12 to 15 years of age, although observations of younger seedlings bearing ovulate strobili have been reported. Male strobili are about 2 cm long and range from yellow to deep red. Female strobili are about 3 cm long and range from deep green to deep red. They have large trident bracts and are receptive to pollination soon after emergence. First-year seedlings survive and grow best under light shade, especially on southerly exposures, but older seedlings require full sunlight. Douglas-fir seeds have a relatively large, single wing and are primarily dispersed by wind and gravity. Most fall within 100 m of the parent tree, but some may travel much greater distances. On rare occasions, sites more than 0.8 km from a seed source have reseeded after cutting. Mice, chipmunks, and squirrels disperse small amounts of seed. Clark's nutcrackers also disperse Douglas-fir seeds. Unretrieved seeds in Clark's nutcracker caches may have a better change of establishment than wind-dispersed seed.

Vegetative regeneration - Rocky Mountain Douglas-fir does not reproduce asexually under natural conditions

Species Distribution


USDA Plants Database
USDA, NRCS. 2016. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.

USFS Plant Database
Habeck, R. J. 1992. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.

Flora of North America
Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 19+ vols. New York and Oxford.

Silvics of North America
Burns, R.M., and B.H. Honkala. 1990. Silvics of North America (Volume 1: Conifers, Volume 2: Hardwoods). USDA Forest Service Agricultural Handbook 654.

The Jepson Herbarium
The Jepson Manual: Vascular Plants of California. B.G. Baldwin, D.H. Goldman, D.J. Keil, R. Patterson, T.J. Rosatti, and D.H. Wilken [editors]. 2012. 2nd edition, thoroughly revised and expanded. University of California Press, Berkeley, CA.

USGS Plant Species Range Maps
Critchfield, W.B., and Little, E.L., Jr., 1966, Geographic distribution of the pines of the world: U.S. Department of Agriculture Miscellaneous Publication 991, p. 1-97. Little, E.L., Jr., 1971-1978, Atlas of United States trees, volume 1,3,13,17, conifers and important hardwoods: U.S. Department of Agriculture Miscellaneous Publications.