Douglas fir is particularly common in the states of Washington and Oregon. In California it is found in the Klamath Mountains as far south as the north-central Sierra Nevada. Its habitat varies from sea level up to a height of 1,800 m.
It belongs to the genus Pseudotsuga, of which it is the best known species. The common name comes from the Scottish botanist David Douglas, who sent the first propagation material in 1827. It is a rapidly growing plant, which allows it to be widely exploited and used in wood production, and adapts to any terrain.
Douglas fir wood is in great demand, but the strength and texture are not uniform: it therefore requires careful selection to have good uniformity. The use is varied especially in construction: boats, bridges, houses, carpentry in general, railway axes, precisely because of its lightness, strength, elasticity and resistance to atmospheric agents.
It is also widely used in the paper industry. A mature Douglas fir also makes a fine ornamental tree and is not difficult to see in parks or gardens, and is also used as a Christmas tree. The height is around 60-75 m and more while the width is also 1.5-2 m in diameter.
The tallest known specimen has been named Doerner Fir, 100.3 m high, located in the East Fork Brummit Creek area in Oregon, the largest is the Queets Fir, with a trunk of 4.85 m diameter, in the Queets River valley, Washington state.
The bark in small trees is thin, smooth, gray containing numerous resinous bubbles. In mature specimens, it is 10–30 cm thick and corky. The shoots are brown to olive green, becoming increasingly dark gray as age increases.
The shoots have a very particular conical shape: about 4-8 mm long, with red-brown scales. The leaves are spirally arranged: the up to 3.5 cm long needles are straight, flexible, flattened, resinous and pleasantly aromatic, green above and greyish below, which, if rubbed, give off a characteristic lemon smell.
The bark contains up to 18% tannin and 6% sugars. Statistically it takes 70-80 years to have a free trunk of 5 m and about 100 years for a free trunk of 10 meters. The production of seeds begins around 20-30 years, since in the previous years it is marked by irregular cycles which sometimes lead to the absence of seed production, sometimes (generally every 5-7 years) to a massive production. Inside each pine cone are kept from 25 to 50 seeds.