Grand Fir

(Abies grandis)

Grand fir occurs throughout the Northern Rockies and in the northern and western parts of the Middle Rockies. It accounts for 2.2 million acres of forested land in Idaho, a significant increase over the past several decades. Brown and Chojnacky (1996) found that the “spruce-firquot; class increased by 177 percent. Data from the Idaho Panhandle National Forests in the Northern Rockies, suggest a 300 percent increase.

Causes of the increase include fire suppression, white pine blister rust, and selective harvesting practices that decreased the historically abundant pines and larch and allowed the shade-tolerant grand fir to increase. On drier grand fir sites, frequent surface fires historically maintained open stands of fire-tolerant ponderosa pine with some Douglas-fir. On cooler and wetter sites where fires were less frequent, open stands of western white pine, Douglas-fir, western larch and sometimes lodgepole pine occurred. Grand fir now dominates on many of these sites.

Grand fir is highly susceptible to drought, wildfire, and several damaging insects and diseases. Extensive mortality periodically occurs from fir engraver beetle, particularly following drought, or when it is infected with root rot. It is also impacted by outbreaks of defoliating insects. In the Northern Rockies and northeastern Middle Rockies, it is highly susceptible to root diseases. And the increase in dense, often multi-storied stands of grand fir also creates a growing risk of large severe fires.

Often mistakenly called the “white fir,” the grand fir is one of seven “true fir” species in the forests of the Pacific Northwest. Once limited in range to northern California and southern Oregon, the grand fir has extended its range significantly, a beneficiary of man’s fire-supression efforts over the years. The grand fir, once the victim of fires that ravished our forests, has extended its growing range into areas that once were dominated by ponderosa pine and other fire-resistant species, now that humans make every effort to quickly supress forest blazes. The grand fir has become one of the most prolific trees in the Idaho forest.

The grand fir is identified by massive, dense foliage that often extends near to the ground. Its flat, blunt needles range from one-half to two inches in length. Grand fir seed cones are cylindrical in shape, and range from two to four inches in length. The greenish hue of the grand fir’s cones make them easy to distinguish from the white fir’s olive-green to purple colored cones.

Grand fir trees grow to heights of 100 to 125 feet, with trunk diameters in the 4- to 6-foot range.

The white, fine-grained wood of the grand fir is used in plywood, as small dimensional lumber, and for paper-making.

Trees of Idaho – Grand Fir