Primarily denizens of mountainous terrain, firs (Abies spp.) are handsome, evergreen conifers. Most species grow in the temperate latitudes of North America, Europe, Asia and Africa, but two species are capable of withstanding especially cold temperatures – a fact that allows them to grow in the harsh boreal regions of North America and Europe.
Classification of Firs
Scientists debate the exact composition of the group, but most recognize approximately 50 different species. Although the group is quite speciose, the constituent species usually occur as “complexes” that share close genetic ties and appearances. In places with more than one species, identification can be challenging.
Despite the similarities of their common names, Douglas firs (Pseudotsugamenziesii) are not true firs at all.
Physical Description and Characteristics
Examination of the needles helps to distinguish fir trees from lookalikes. Fir needles are generally soft to the touch, flat in cross section and attach to the branch via suction-cup-like structures. If you pluck a needle from a branch, it will usually separate cleanly, without leaving a small peg behind as, for example, spruce trees (Picea spp.) do. The needles of firs often persist for a considerable length of time. Many species retain their leaves for five years or more, and some – notably Pacific silver firs (Abies amabilis) – may retain their leaves for decades.
While young, most fir trees exhibit a pyramidal growth habit and dark green foliage. Fir branches emerge from the central trunk in a whorled pattern. Because most firs produce a new set of whorls each year, you can often determine the approximate age of the trees by counting the whorls, although this may not be effective for specimens of advanced age. Further highlighting the specific growth habits of the species, each living branch usually grows in the same fashion each year: A longer terminal branch and two lateral branches are produced on each. Although the branches of some Nordmann firs (Abies nordmanniana) droop slightly, those of most firs do not.
In addition to their handsome foliage and growth habit, firs have incredible looking cones, which stand upright on the branches. Many firs produce cones at a relatively early age, especially Korean firs (Abies koreana), which often produce cones by the time they reach 2 feet in height. Most fir cones start out blue or purple in color, although they darken with age.
The cones are resinous and occur on year-old branches. Maturation of the cones, which grow to almost 10 inches in some species, takes but a single season. Unfortunately, the cones of firs fall apart to release their seeds once they mature – a condition that botanists refer to as dehiscent.
Free Range Firs
Wild firs typically occur on good sites, with ample soil moisture and deep, fertile soils. Firs grow relatively quickly, but they are not especially long-lived trees. While occasional examples may survive nearly 500 years, most such specimens are capable of doing so because they spend many years suppressed by the dense shade produced by mature trees. Most firs are moderately sized trees, but a few – particularly the grand fir (Abies grandis) – exceed 200 feet in height. Most firs have relatively thin, flaky bark, which offers them little protection against fire.
Unlike many other conifers, whose woods possess insect- and decay-resistant qualities, fir wood degrades quickly once harvested. Accordingly, fir wood is rarely grown for timber production. It is primarily used to produce pulp, although some craftsmen use it for indoor applications. Unsurprisingly given their growth habit and aesthetic appeal, fir trees are frequently farmed for use as Christmas trees.