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Douglas Fir
Home  > Tree Identification  > Douglas Fir

Douglas-fir; Red-fir; Douglas-spruce

Pseudotsuga menziesii

Douglas-fir tree
Nicknamed the “Oregon Pine” due to its value as a timber tree, the Douglas-fir is not a pine, or even a true fir tree. In fact, its characteristics are unique enough to warrant the Douglas-fir being classified in its own genus.

There are two varieties of Douglas-fir, the Rocky Mountain variety (P. menziesii var. menziesii) and the Blue Douglas-fir (P. menziesii var. glauca). Each variety of Douglas-fir has its own attributes and faults. The Rocky Mountain Douglas-fir has green needles, grows faster and taller, and is less susceptible to Rhabdocline needlecast disease. The Blue Douglas-fir has blue-green needles, is more cold-hardy, and is more tolerant to shade than the Rocky Mountain variety.

Like most coniferous trees, the Douglas-fir should be planted in full sun, but they will tolerate some shade. The tree is conical when young and the crown will become more rounded as the tree matures. Douglas-fir can be planted as a specimen tree or, due to its thick branching habit, makes a good screening tree.

Most Douglas-fir trees planted in a landscape setting will reach 40-80 feet tall and 15-25 feet wide at maturity. Height growth may be slow for the first 5 years after planting as the tree becomes established in its new location. In its natural forest habitat the Douglas-fir can become very tall. The tallest Douglas-fir was found near Little Rock, WA and was 330 feet tall. These trees can live for hundreds of years, with the oldest Douglas-fir, near Mount Vernon, WA being aged at over 1400 years old.

Douglas-fir trees grow best in moist, well drained soils. If they are planted in poorly drained, clay soils their growth will suffer and they will be more prone to insect and disease attacks. Douglas-fir trees do have a tap root, but overall the tree is fairly shallow rooted, with most fine and lateral roots being located in the upper 8 inches of the soil profile.

Douglas-fir cone-needlesThe needles of Douglas-fir range from 0.75 to 1.25 inches long. They may range from dark yellow-green to dark bluish-green in color and have a soft texture. Douglas-fir needles can remain on a tree for up to 8 years and have often been described as fragrant and fresh smelling.

Douglas-fir coneThe Douglas-fir produces a cone that is 3 to 4 inches in length. The cones are often used as an identifying feature of Douglas-fir due to a three-pronged bract that protrudes from under each scale of the cone. The bracts are green on young cones, but when the seeds are mature the bracts turn brown.


Douglas-fir tree2

The tree bark of young Douglas-fir trees is a smooth, dark, gray-brown with resin blisters. As the tree bark matures it becomes thick, reddish-brown, with deep irregular fissures.

The two most common insect pests that attack Douglas-fir trees are the Tussock Moth (Orgyia pseudotsugata) and the Western Spruce Budworm (Choristoneura fumiferana). Older Douglas-fir trees may be damaged by the Douglas-fir Beetle (Dendroctonus pseudotsugae).

The most serious foliar disease of Douglas-fir is the needlecast caused by Rhabdocline pseudotsugae. Cool, wet weather promotes infection by needlecast, but fungicide treatments can prevent or reduce significant needle loss. Douglas-fir stems may also be attacked by Dwarf Mistletoe (Arceuthobium douglasii).

The roots and trunks of Douglas-fir may be attacked by a number of fungal pathogens. Most common are Shoestring Root Rot (Rhizina undulata), Laminated Root Rot (Phellinus weirii), and Red Ring Rot (Phellinus pini). Infection by these tree root and trunk diseases may cause Douglas-fir trees to be blown over in wind storms.

The native geographic range of Douglas-fir starts on Vancouver Island in Canada and continues south through Washington, Oregon, California, Idaho, Montana, Wyoming, Utah, Nevada, Colorado, New Mexico, Arizona, Texas, and on into northern Mexico. Douglas-fir has been planted throughout much of the northern and central United States east of the Rocky Mountains as a landscape tree.

Douglas-fir characteristics:

Common insect pests of Douglas-fir: Tussock Moth (Orgyia pseudotsugata); Western Spruce Budworm (Choristoneura fumiferana); Douglas-fir Beetle (Dendroctonus pseudotsugae).

Common disease pests of Douglas-fir: Needlecast (Rhabdocline pseudotsugae); Dwarf Mistletoe (Arceuthobium douglasii); Shoestring Root Rot (Rhizina undulata); Laminated Root Rot (Phellinus weirii); Red Ring Rot (Phellinus pini).

Fruit: 3 to 4 inch long cone with three-pronged bracts under each cone scale

Growth Rate: Moderate to fast

Needles: 0.75 to 1.25 inches long

Mature height: 40 to 80’

Preferred soil pH: 5.0 - 7.5

Summer foliage: Dark yellow-green to dark bluish-green

Tree Bark: Smooth, dark, gray-brown with resin blisters on young trees, maturing to thick, reddish-brown, separated by deep irregular fissures.

USDA Hardiness Zone: 4 - 6

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