Pseudotsuga menziesii, commonly known as Douglas fir, Douglas-fir and Oregon pine, is an evergreen conifer species native to western North America. One variety, the coast Douglas fir, grows along the Pacific Ocean from central British Columbia south to central California. A second variety, the Rocky Mountain Douglas fir, grows in the Rocky Mountains from British Columbia south to Mexico. The tree is dominant in western Washington and Oregon. It is extensively used for timber, worldwide.
The common name honors David Douglas, a Scottish botanist and collector who first reported the extraordinary nature and potential of the species. The common name is misleading since it is not a true fir, i.e., not a member of the genus Abies. For this reason the name is often written as Douglas-fir (a name also used for the genus Pseudotsuga as a whole).
The specific epithet, menziesii, is after Archibald Menzies, a Scottish physician and rival naturalist to David Douglas. Menzies first documented the tree on Vancouver Island in 1791. Colloquially, the species is also known simply as Doug-fir or as Douglas pine (although the latter common name may also refer to Pinus douglasiana).
Douglas firs are medium-size to extremely large evergreen trees, 20–100 metres (70–330 ft) tall (although only coast Douglas firs reach such great heights). The leaves are flat, soft, linear, 2–4 centimetres (3⁄4–1 1⁄2 in) long, generally resembling those of the firs, occurring singly rather than in fascicles; they completely encircle the branches, which can be useful in recognizing the species. As the trees grow taller in denser forest, they lose their lower branches, such that the foliage may start high off the ground. Douglas firs in environments with more light may have branches much closer to the ground.
The female cones are pendulous, with persistent scales unlike true firs. They are distinctive in having a long tridentine (three-pointed) bract that protrudes prominently above each scale (it resembles the back half of a mouse, with two feet and a tail).
One variety, coast Douglas fir (Pseudotsuga menziesii var. menziesii), grows in the coastal regions, from west-central British Columbia southward to central California. In Oregon and Washington, its range is continuous from the eastern edge of the Cascades west to the Pacific Coast Ranges and Pacific Ocean. In California, it is found in the Klamath and California Coast Ranges as far south as the Santa Lucia Range, with a small stand as far south as the Purisima Hills in Santa Barbara County. In the Sierra Nevada, it ranges as far south as the Yosemite region. It occurs from near sea level along the coast to 1,800 m (5,900 ft) above sea level in the mountains of California.
Further inland, coast Douglas fir is replaced by another variety, Rocky Mountain or interior Douglas fir (P. menziesii var. glauca). Interior Douglas fir intergrades with coast Douglas fir in the Cascades of northern Washington and southern British Columbia, and from there ranges northward to central British Columbia and southeastward to the Mexican border, becoming increasingly disjunct as latitude decreases and altitude increases. Mexican Douglas fir (P. lindleyana), which ranges as far south as Oaxaca, is often considered a variety of P. menziesii.
Douglas-fir prefers acidic or neutral soils. However, Douglas fir exhibits considerable morphological plasticity, and on drier sites coast Douglas fir will generate deeper taproots. Interior Douglas fir exhibits even greater plasticity, occurring in stands of interior temperate rainforest in British Columbia, as well as at the edge of semi-arid sagebrush steppe throughout much of its range, where it generates even deeper taproots than coast Douglas fir is capable.
Mature or "old-growth" Douglas fir forest is the primary habitat of the red tree vole (Arborimus longicaudus) and the spotted owl (Strix occidentalis). Home range requirements for breeding pairs of spotted owls are at least 400 ha (4 square kilometres, 990 acres) of old-growth. Red tree voles may also be found in immature forests if Douglas fir is a significant component. This animal nests almost exclusively in the foliage of Douglas fir trees. Nests are located 2–50 metres (5–165 ft) above the ground. The red vole's diet consists chiefly of Douglas fir needles. A parasitic plant sometimes utilizing P. menziesii is Douglas-fir dwarf mistletoe (Arceuthobium douglasii).
The leaves are also used by the woolly conifer aphid Adelges cooleyi; this 0.5 mm long sap-sucking insect is conspicuous on the undersides of the leaves by the small white "fluff spots" of protective wax that it produces. It is often present in large numbers, and can cause the foliage to turn yellowish from the damage it causes. Exceptionally, trees may be partially defoliated by it, but the damage is rarely this severe. Among Lepidoptera, apart from some that feed on Pseudotsuga in general (see there) the gelechiid moths Chionodes abella and C. periculella as well as the cone scale-eating tortrix moth Cydia illutana have been recorded specifically on P. menziesii.
The coast Douglas fir variety is the dominant tree west of the Cascade Mountains in the Pacific Northwest, occurring in nearly all forest types, competes well on most parent materials, aspects, and slopes. Adapted to a moist, mild climate, it grows larger and faster than Rocky Mountain Douglas fir. Associated trees include western hemlock, Sitka spruce, sugar pine, western white pine, ponderosa pine, grand fir, coast redwood, western redcedar, California incense-cedar, Lawson's cypress, tanoak, bigleaf maple and several others. Pure stands are also common, particularly north of the Umpqua River in Oregon.
This plant has ornamental value in large parks and gardens.
Away from its native area, it is also extensively used in forestry as a plantation tree for timber in Europe, New Zealand, Chile and elsewhere. It is also naturalised throughout Europe, Argentina and Chile (called Pino Oregón), and in New Zealand sometimes to the extent of becoming an invasive species (termed a wilding conifer) subject to control measures.
This was the preferred species for Hawaiian war canoes. The Hawaiians, of course, did not log the trees; they had to rely on driftwood.
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