Difference Between Firs And Douglas Firs
Firs have a striking pyramid shape, similar to that of spruces, with which they are sometimes confused. They can be distinguished by their needles, which do not grow from peglike stalks (as do those of spruces), but directly from the main branch from bases shaped like suction cups. Older branches are marked by circular scars in places where needles have fallen. The cones are held upright on short, woody spikes that remain on the branch after the mature cone falls apart.
Of the 40 to 50 species of firs, 10 are native to North America, primarily west of the Rocky Mountains. Several of these grow more than 200 feet (60 meters) tall. These towering giants include the white fir (Abies concolor), the noble fir (A. nobilis), the California red fir (A. magnifica), and the Pacific silver fir (A. amabilis). Few are used for lumber or paper pulp, since the wood of true fir is inferior to that of spruce or pine. North America’s classic “Christmas tree” is the balsam fir of the eastern states and provinces. It can grow to up to 60 feet (18 meters) when mature, but is usually harvested at “living room” height.
The six species of Douglas firs (genus Pseudotsuga) are distinct from the true firs (genus Abies). Douglas firs can be recognized by their distinctive yellow-green or blue-green needles. Each needle is long and flat, with a groove down its center and a short stalk at its base. They grow in spirals attached directly to the tree’s branches. The seed cones of the Douglas fir are long and slender, and hang from the underside of its branches.
Douglas firs grow throughout western North America and eastern Asia. They are named after their discoverer, Scottish botanist David Douglas. (Douglas found many new animal and plant species when he explored British Columbia in the 1820s and 1830s.) As mentioned previously, Douglas firs are the most-important timber trees in North America. They are harvested and grown throughout the Pacific Northwest, where they reach heights of 330 feet (100 meters), with widths of 15 feet (4.5 meters) around the base of the trunk.
Douglas firs do not begin producing seeds until they are about 25 years old. Thereafter, they produce huge crops of cones every five to seven years. The long, drooping cones mature in one season and drop intact to the forest floor.