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Douglas-Fir

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SCIENTIFIC NAME: Pseudotsuga menziesii
FAMILY: Pinaceae

This Tree in Colorado: Douglas-fir is one of the noblest forest trees. It is a high valued timber species because of the strength of its wood. In Colorado it grows naturally with ponderosa pine and lodgepole pine forests, especially on the moister and cooler north facing slopes. It prefers full sunlight. Because of its ability to maintain needles (5-8 years) and its compact branching habit, Douglas-fir is often a favorite Christmas (Holiday) Tree.

Hardiness: Zones 4 to 6. Does well on sunny sites.

Growth rate: Douglas-fir grows at a medium rate (1 to 2 feet per year) depending on site conditions. In Colorado, normal height is around 100 feet, with the tallest being 138 feet. It has a pendulous look to the branches and forms an upright conical appearance.

Foliage: Single needles, flat, blunt. About 1 inch in length.

Cones: Significant. Ornate. Hangs down. About 3 inches in length. Three-pointed seed bracts extend beyond cones scales giving the cone a distinctive look.

Bark: Young bark is smooth and light colored with resin blisters. Older trunks often divided into thick reddish-brown ridges separated by deep fissures.

Insects and diseases: Recently there has been an abundance of insects attacking the native stands of Douglas-fir. Spruce budworm, Tussock moth and Douglas-fir beetle. This tree is also the alternate host for Cooley spruce-gall adelgid. On Douglas-fir the young adults feed on the new foliage before flying to spruce trees to complete their life cycle.

Landscape value: Douglas-fir can be a nice substitute for blue spruce, however, it does not grow as densely foliaged. It may struggle some in the heavy clay soils found in most urban areas. It would be great for a Holiday tree garden (grove). This is not a common tree in the nursery trade.

Best advice: Use in groups as a screen planting along fences or property boundaries. As a single planting, give it space to grow. Do not plant within 10 feet of homes or driveways/roads.

Information sources:
– Michael Dirr, Manual of Woody Landscape Plants (University of Georgia, 1990)
– Michael Kuhns, Trees of Utah and the Intermountain West (Utah State University Press, 1998)