Douglas-fir is not a true fir and has been a taxonomic nightmare for those trying to settle on a genus name. After changing names on numerous occasions the present scientific name Pseudotsuga menziesii now uniquely belongs to Douglas-fir.

To make things even more complicated two different varieties of the species are recognized. There is the P. menziesii var. menziesii, called coast Douglas-fir, and P. menziesii var. glauca called Rocky Mountain or blue Douglas-fir.
The unusual cone is also unique with, forked, snake-tongue-like bracts extending from each scale. The tree is one of the dominant trees in the foothills of the Rocky Mountains, and up the slopes to medium altitudes. It has been transplanted successfully throughout most of the North American temperate zone.

Douglas-Fir grows 40 to 60 feet and spreads 15 to 25 feet in an erect pyramid in the landscape. It grows to more than 200 feet tall in its native habitat in the West. Hardiness varies with seed source, so be sure it was collected from an area with suitable coldhardiness to the area in which it will be used.

Pests: Aphids infestations on small trees may be dislodged with a strong stream of water from the garden hose. Scale and bark beetles may infest Douglas-Fir, especially those under stress.

Diseases: Root rot can be a serious problem on clay and other wet soils. Needles infected by leaf cast fungi in spring turn brown and fall off. Several fungi cause canker diseases leading to branch dieback. Maintain tree health and prune out infected branches.

(Info courtesy of www.forestry.about.com)

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