Douglas-fir
(Pseudotsuga menziesii)
Range
In the United States, Douglas-fir grows in most forests from the Rocky Mountains to the Pacific coast and from the Mexican to Canadian borders. Botanically it is not a true fir. It reaches its largest size and fastest rate of growth in Washington and Oregon, where large trees form very dense forests that sometimes yield as much as 100,000 board-feet of lumber per acre.
Properties
Most old-growth Douglas-fir from the Pacific coast and northern Rocky Mountain States is moderately heavy, very stiff, moderately strong, and moderately shock resistant. It averages about 33 pounds a cubic foot. The wood is also moderately hard, with an average specific gravity ranging from 0.40 to 0.48. Wide-ringed second-growth Douglas-fir from the coastal States and material grown in the southern Rocky Mountain States tends to be lighter in weight and to have lower strength properties.
The wood of Douglas-fir can be readily kilndried if proper methods are used. Although it is more difficult to work with handtools than the soft pines, it holds fastenings well and can be glued satisfactorily. Dense heartwood has moderate decay resistance.
Uses
The principal uses of Douglas-fir are for lumber, timbers, piling, and plywood. Remanufactured lumber. goes mostly into sash, doors, general millwork, railroad car construction and repair, and boxes and crates. Plywood is now in wide use for sheathing, concrete forms, prefabricated house panels, millwork, ships and boats, and other structural forms. Chipped Douglas-fir sawmill residue has a considerable market at pulp mills.
Description
Heartwood is orange red to red or sometimes yellowish. Resin canals, which are seen as brownish streaks in the summerwood, appear to be more abundant and more readily detectable than in western larch. Transition from springwood to summerwood is similar to that in western larch. The heartwood of Douglas-fir may be confused with that of the southern yellow pines, but resin canals are larger and much more abundant in southern pines. Most Douglas-fir has a distinctive odor.