Identify Douglas-Fir

Doug Fir, a Taxonomic Nightmare

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Doug Fir Cone. Steve Nix

Douglas-fir or Doug fir is the English name applied in common to most evergreen coniferous trees of the genus Pseudotsuga which is in the family Pinaceae. There are five species, two in western North America, one in Mexico, and two in eastern Asia.

Douglas Fir is Confusing to Taxonomists

The fir's most common name honors a Scottish botanist by the name of David Douglas, a collector of botanical specimens who first reported the extraordinary nature and potential of the species.

On his second expedition to North America's Pacific Northwest in 1824, he discovered what was to eventually be scientifically named Pseudotsuga menziesii.

Because of its distinctive cones, Douglas-firs were finally placed in the new genus Pseudotsuga (meaning "false Tsuga") by the French botanist Carrière in 1867. The Doug-firs gave 19th-century botanists problems due to their similarity to various other conifers better known at the time; they have at times been classified as Pinus, Picea, Abies, Tsuga, and even Sequoia.

The Common North American Douglas-fir

Douglas fir is one of the most important timber trees on earth in terms of forest products. It can grow large over centuries but will usually be harvested within in a century because of its wood value. The good news is that it is a common non-endangered tree and the most plentiful western conifer in North America.

This common "fir" has two Pacific coastal and Rocky Mountain variants or varieties.

The coastal tree grows to a height of 300 feet where the Rocky Mountain variety only reaches 100 feet. 

  • Pseudotsuga menziesii var. menziesii (called coastal Douglas fir) grows in the moist coastal regions from west-central British Columbia southward to central California. These firs in Oregon and Washington range from the eastern edge of the Cascade mountain range to the Pacific ocean.
  • Pseudotsuga menziesii var. glauca (called Rocky Mountain Douglas fir) is a smaller fir that tolerates drier sites and grows along with the coastal variety and throughout the Rocky Mountains to Mexico.

Quick Identification of Douglas-fir

Douglas-fir is not a true fir so both the needle formations and the unique cone can throw you off. If you look at my included image, you will see unique snake tongue-like forked bracts creeping out from under the cone scales. These cones are nearly alway intact and plentiful both on and under the tree.

True firs have needles that are upturned and not whorled. Doug-fir is not a true fir and needles are singly wrapped around the twig and between 3/4 to 1.25 inches long with a white line underneath. The needles are deciduous (but may persist), linear or needle-like, not prickly like spruce and singly whorled around the twig.

Doug fir is also a favorite Christmas tree and adapts well to commercial plantations well out of its natural range. You may want to review the Essential Douglas-fir with images.

The Most Common North American Conifer List

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Nix, Steve. "Identify Douglas-Fir." ThoughtCo, Mar. 28, 2017, thoughtco.com/identify-douglas-fir-1341853. Nix, Steve. (2017, March 28). Identify Douglas-Fir. Retrieved from https://www.thoughtco.com/identify-douglas-fir-1341853 Nix, Steve. "Identify Douglas-Fir." ThoughtCo. https://www.thoughtco.com/identify-douglas-fir-1341853 (accessed December 18, 2017).