Douglas-Fir

 

Scientific Name: Pseudotsuga menziesii

Douglas Fir

Description: Douglas-fir trees, which are also called red firs, Oregon pines, and Douglas spruce, are neither true fir trees nor pines nor spruces! The scientific genus name Pseudotsuga means “false hemlock,” alluding to another kind of tree that Douglas-firs are similar too. Douglas-firs are evergreen trees, meaning that they keep their needle-like leaves year round. There are two varieties of this species, coast Douglas-fir and Rocky Mountain Douglas-fir, which are differentiated by their habitats, growth rates, and physical characteristics. When Douglas-firs grow in dense forests, they self-prune their lower branches so that the conical crown starts many stories above the ground. Trees growing in open habitat, especially younger trees, have branches much closer to the ground.

Size: Coast Douglas-firs are the faster-growing and larger of the two varieties. They commonly grow up to 250 feet in old-growth forests and can reach 5 to 6 feet in diameter. Rocky Mountain Douglas-firs measure about the same in diameter but only grow up to 160 feet.

Typical Lifespan: The largest coast Douglas-firs frequently exceed over 500 years in age and occasionally over 1,000!

U.S. Habitat and Range: The two Douglas-fir varieties grow in very different habitats, as evidenced by their names. Rocky Mountain Douglas-firs are the inland variety that grow in the mountainous Pacific Northwest and in the Rocky Mountains. They are much more cold tolerant than the coast Douglas-fir, which is suited to moist, mild climates on the west coast.

Life History and Reproduction: Douglas-firs are conifers, which means that they produce seeds in cones rather than in flowers. The seeds have a single wing and are wind-dispersed. Douglas-fir seeds provide food for a number of small mammals, including chipmunks, mice, shrews, and red squirrels. Many songbirds eat the seeds right out of the cone, and raptors like northern spotted owls rely on old-growth forests of Douglas-firs for cover. One species that relies on Douglas-firs almost exclusively is the red tree vole. These tiny rodents seek cover in nests constructed in the crowns of Douglas-firs and eat the needles. Red tree voles even obtain their water source from the tree by licking moisture off the needles!

Fun Fact: Douglas-firs were used by American Indians for building, basketry, and medicinal purposes. Ailments that Douglas firs were used to cure include stomach aches, headaches, rheumatism, and the common cold.

Conservation Status: Stable. Many people are familiar with Douglas-firs, because they are one of several species used as Christmas trees. Aside from their use as holiday decorations, Douglas-firs are one of the most valuable timber resources in the country. They’re used for furniture, poles, fences, and flooring, just to name a few. Although they are harvested extensively for timber, Douglas-firs are widespread and aren’t in danger of extinction. However, when the trees are cut down, rare wildlife species like northern spotted owls lose valuable habitat.

Sources:

USDA Forest Service Fire Effects Information System
USDA Forest Service Silvics of North America
USDA NRCS Plant Guide
USDA NRCS Fact Sheet

 

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