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.
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