Pseudotsuga menziesii is an evergreen conifer species in the pine family, Pinaceae. It is native to western North America and is known as Douglas fir, Douglas-fir, Oregon pine, and Columbian pine. There are two varieties: coast Douglas-fir (P. menziesii var. menziesii), and Rocky Mountain Douglas-fir (P. menziesii var. glauca).
The massive mega-genome of Douglas fir has been sequenced in 2017 by the large PineRefSeq consortium revealing a specialized photosynthetic apparatus in the light harvesting complex genes which may explain its exceptional shade tolerance.
The female cones are pendulous, with persistent scales, unlike those of 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).
Pseudotsuga menziesii var. menziesii, the coast Douglas-fir, 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. One of the last remaining old growth stands of conifers is in the Mattole Watershed, and is under threat of logging. 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.
Another variety exists further inland, Pseudotsuga menziesii var. glauca, the Rocky Mountain Douglas-fir or interior Douglas-fir. 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.
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.
The species is extensively used in forestry as a plantation tree for softwood timber. The timber is used for joinery, veneer, flooring and construction due to its strength, hardness and durability. It is also naturalised throughout Europe, Argentina and Chile, and in New Zealand sometimes to the extent of becoming an invasive species (termed a wilding conifer) subject to control measures.