904 Pseudotsuga menziesiiCommon Names: Douglas-fir, Douglasfir Family: Pinaceae (pine Family)
Douglas-fir is a huge and stately evergreen conifer, the largest member of the pine family, in fact. Specimens more than 300 ft (91.4 m) tall with trunk diameters exceeding 15 ft (4.6 m) are known. The National Champion, in Oregon, is 329 ft (100.3 m) tall. Some of the larger trees are believed to be over a thousand years old. The tall, straight trunk can be free of branches for a third of its length. The bark on young trees is smooth and ashy gray; that on mature trees is reddish brown and broken into longitudinal plates; really large trees can have bark more than 12 in (30.5 cm) thick. The grayish green needles are flattened, quite soft, about 1 in (2.5 cm) long, and arranged all around the twigs like a bottle brush. The cones are oval and pendulous, 2-4 in (5.1-10.2 cm) long and each scale has a conspicuous three-pointed bract that gives the cone an overall spiny look. These trident shaped bracts are unique to the Douglas-firs. Pseudotsuga menziesii var. glauca, the Rocky Mountain Douglas-fir, is a smaller tree with smaller cones, bluish needles and occurs at higher elevations than the coastal variety (var. menziesii).
There are several cultivars selected for their slow growth rates and small stature; many never exceed 60 ft (18.3 m) in height. 'Fastigiata' has crowded, upright pointing branches. 'Pendula' is a weeping cultivar with branches that hang in flat panes. 'Fletcheri' is a spreading dwarf cultivar that gets only 6 ft (1.8 m) tall.
Rocky Mountain Douglas-fir grows naturally throughout the Rocky Mountains from British Columbia to northern Mexico. The coastal variety grows west of the mountain ranges from British Columbia to central California. One of the most abundant trees in western North America, Douglas-firs grow from sea level to 10,000 ft (304.8 m), and in climates that get just 15 in (38.1 cm) of precipitation annually, to climates that average more than 100 in (254 cm) of precipitation a year. It often grows in pure to nearly pure stands. Douglas-fir is a widely grown and very popular ornamental in Great Britain. It has been planted in New Zealand as a timber crop and is now considered an invasive weed there.
CultureUnder ideal conditions, Douglas-fir can grow 35 ft (10.7 m) tall in 20 or 25 years. Light: Douglas-fir can tolerate partial shade, but it does best in full sun. Moisture: In cultivation, Douglas-fir is not tolerant of drought. They grow best in humid climates. The typical variety, (P. menziesii var. menziesii) which grows in the western Cascades, is not at all tolerant of drought. Rocky Mountain Douglas-fir (var. glauca) is a little more tolerant of dry conditions. Hardiness: USDA Zones 4 - 7. The Rocky Mountain variety is more cold hardy and better adapted to conditions in the northern and central U.S. than is the typical, coastal variety. The coastal variety is better for warmer climates. Propagation: Douglas-firs start bearing cones at the tender age of 10 years and continue to produce nearly every year of their lives. They scatter their seeds annually and quickly cover any recently burned or cleared ground. Start seeds outdoors in containers in spring. The named cultivars usually are grafted onto seedlings.
Douglas-firs, with their dense foliage and symmetrical pyramidal form are attractive ornamentals, used extensively as specimens and wind breaks in the northern U.S. and Europe. Large trees are imposing specimens. Planted close together and pruned, Douglas-firs make fine evergreen hedges. Young Douglas-firs, whose needles remain on the tree long after it is cut, are excellent as Christmas trees, and the Rocky Mountain variety especially, is widely grown for that purpose.
One of the most important timber trees in North America, Douglas-fir is used for railroad ties and all kinds of construction. The wood of Douglas-fir is resistant to decay, does not warp, and is stronger for its weight than that of any other American tree. Since the trees are so huge, it is possible to get very large beams and boards that are totally free of defects and knots. The largest beams are used for structural trusses in bridges, docks and large buildings. They make great flag poles too. At the 1915 Panama Pacific International Exposition, Oregon displayed a flag pole from a single Douglas-fir (their State Tree) that was a little more than 299 ft (91.1 m) long.
The seeds of Douglas-fir are a very important food source for native wildlife. The Douglas squirrel, Townsend chipmunk, red-winged crossbill, Clark's nutcracker, and dark-eyed junco are just a few of the many critters that eat large quantities of Douglas-fir seeds. The blue grouse eats the needles.
Douglas-fir was first discovered in 1791 by the physician and botanist, Archibald Menzies, who is honored in the botanical name. It was introduced to England in 1827 by the Scot, David Douglas, who is honored by the common name. There are only five species in the genus. Pseudotsuga means "false hemlock"; they differ from the true hemlocks (Tsuga) in having hanging, rather than erect, cones. Bigcone Douglas-fir (P. macrocarpa) occurs naturally only in cool mountain canyons in a small area of southern California. The other three species of Douglas-firs occur in eastern Asia.
Steve Christman 1/18/01; updated 12/2/03, 11/1/06