Botanical properties
The Douglas Fir is a very tall tree that can reach over 50 m in height. The crown of the Douglas Fir is pointed and only flattens out late.
- The branches are arranged in long hanging whorls. The entire branch is soft to the touch and very fragrant (smelling of citronella). The buds are numerous, spindle-shaped, long, brownish-red and shiny.
- The needles of the Douglas Fir are thin and flat, in a clear pectinate arrangement, and have two white bands on the bottom. The tips are quite angled but soft and are bright green on the top and paler on the bottom.
- The cones hang down and are from 5 cm to 12 cm long. They have distinctive, long, 3-pointed bracts that extend past the cone’s scales.
Seeds are triangular, from 6 to 8 mm long, and reach maturity in the autumn. - The appearance of the bark varies depending on the age of the tree: on a young tree, it is thin and smooth, grey-brown, with pockets of resin; on an older tree, it is very thick, cork-like, reddish-brown and scaly. The overall proportion in volume is almost 15%.
- Douglas Fir wood has a salmon-pink to reddish-brown heartwood. Its sapwood is paler and clearly differentiated. The texture is coarse and the grain is straight.
- The rings of the Douglas Fir are well marked, with the spring wood and summer wood distinct from one another. The texture, between 30 and 45% (ratio between the length of the final timber and the total width of the ring) is stable, whatever the speed of growth, which gives the Douglas Fir good mechanical properties.
From a microscopic point of view
Like other conifers, the Douglas Fir produces a wood made up essentially of tracheids, which simultaneously carry out a sap conduction and mechanical support role. The tracheids formed in springtime have bigger cross-sections and thinner walls than those formed in summertime. The growth rings are clearly visible, often with wide summer wood. To the naked eye, on the end grain, it is often possible to pick out three parts in a growth ring with a transition area between spring wood which is light and soft, and summer wood, which is dark and hard. The walls of the tracheids have characteristic spiralled thickenings. The wood of the Douglas Fir contains longitudinal resin canals, mostly in the late wood, and radial resin canals with polygonal cross-sections in the thick wood rays. Wood rays that do not contain radial canals are uniseriate (only one cell wide). They contain radial parenchyma and small radial tracheids.
