Douglas-fir (Pseudotsuga menziesii): how to identify it

Coast and Rocky Mountain Douglas-fir

The Forest Service recognizes two varieties, and which one you meet depends on where you stand.

Coast Douglas-fir (var. menziesii) is the green variety. It grows faster and becomes much larger. Old-growth trees commonly reach 250 feet (76 m) tall and 60 to 72 inches (150 to 180 cm) across, and the tallest on record, near Little Rock, Washington, measured 330 feet (100.5 m) (Silvics). Ages over 500 years are not uncommon on the coast, some trees have passed 1,000, and the oldest authenticated tree was slightly more than 1,400 years old when it was cut.

Rocky Mountain or blue Douglas-fir (var. glauca) is the interior variety: more shade tolerant and more cold hardy, according to the Forest Service. NRCan describes its needles as distinctly bluish-green, often sharp-pointed, kept on the tree for 5 to 8 years, and its cones as under 8 cm with bracts usually bent back. It grows to 40 m (130 ft) and 300 years in Canada, in colder, drier mountains than the coast variety, with principal branches that are more ascending. Interior trees typically reach 100 to 120 feet in 200 to 300 years (Silvics).

The range is an upside-down V. The Forest Service maps the shorter arm along the Pacific Coast Ranges for about 1,367 miles (2,200 km), south to about 34° 44' N in California, and the longer arm along the Rocky Mountains for nearly 2,800 miles (4,500 km), into central Mexico. The northern tip is near 55° N in British Columbia. Planted Douglas-firs grow well outside this range, so a tree in a park far from the West can still be one; Virginia Tech notes the range may be expanded by planting.

For the forests where it grows with western hemlock, western redcedar and Sitka spruce, the Pacific Northwest tree guide sorts the region's trees by zone.

Douglas-fir vs true fir, hemlock and spruce

Three groups get confused with Douglas-fir. The cone separates all of them; the needles work when the cones are out of reach.

True firs. Ohio State University Extension's Is It Pine, Spruce, or Fir? describes fir cones that "remain upright or erect" and break apart around a central stalk that stays on the tree, so whole fir cones are rarely found on the ground. A fir needle has a round base like a "suction-cup tipped dart." A whole cone under the tree, with bracts poking out, rules out a true fir. The spruce vs fir guide runs the same tests on balsam and Fraser fir.

Western hemlock. Virginia Tech's western hemlock fact sheet lists Douglas-fir's closest look-alike as having flat needles only 1/4 to 3/4 inch long with two white bands beneath, and egg-shaped cones about 1 inch long. The hemlock page covers it in full.

Spruces. Spruce needles are four-sided and sit on short woody pegs, and spruce cones hang and often fall intact (Ohio State), which is why a Douglas-fir cone gets mistaken for one. Turn the cone over: spruce scales are thin and nothing sticks out between them.

Douglas-fir as a Christmas tree and in the yard

On a tree lot, a cut Douglas-fir has no cones, so use the needles and buds: soft, fragrant single needles with no peg, and sharp red-brown buds at the tips. Compare with a Fraser or balsam fir beside it, whose needles leave a flat round scar when pulled (Ohio State).

In a yard or park, the cone remains the easiest proof. Look under the tree after late summer, when cones mature (Virginia Tech) and start to drop. One cone with mouse tails is enough.

Tree Identifier names a tree from one photo, and Douglas-fir is among the 138 species in the app's Collection. The best photo is a fallen cone held in your hand with the bracts visible, or a twig tip showing the bud. The app shows no confidence score and no look-alike list, so check a Douglas-fir answer against the cone and bud tests above, and ask the follow-up chat if you need to tell coast from Rocky Mountain trees. For the other needle trees, the conifer identification key sorts pines, spruces, firs, hemlocks and larches with three questions.