Douglas-fir (Pseudotsuga menziesii) is the state tree of Oregon and one of the tallest trees on Earth. The tallest living individual is the Brummitt fir in Oregon’s Coos County. It stands about 329 feet tall. Only coast redwood and Australian mountain ash reach greater heights based on current knowledge of living trees. I was first introduced to Douglas-fir in 1995 on a pruning job with a nursery. I noticed and appreciated the soft texture and blue-green foliage of Douglas-fir in the customer’s yard. This specimen was about 20 feet tall at that time.
The common name honors David Douglas, the Scottish botanist who first introduced the tree into cultivation in 1826. The hyphen in the common name indicates that Douglas- fir is not a true fir — they are not members of the genus Abies. Because of the distinctive cones, Douglas-fir was placed in the genus Pseudotsuga (meaning false hemlock) by the French botanist Carriere in 1867. Douglas-fir is in the Pinaceae; other members of Pinaceae include pines, firs, spruces, larch and hemlock.
Name: Pseudotsuga menziesii
Common name: Douglas-fir
Hardiness: Zones 4 to 7
Mature height: Up to 250 feet or more in the wild; 40 feet to 80 feet in cultivation
Mature spread: About 10 feet to 15 feet
Landscape use: Arboretums, yards, parks, cemeteries
Ornamental characteristics: Flat, soft needles; small pendulous cones; bluegreen foliage
The leaves of Douglas-fir are flat and needle-like, resembling those of the firs. The cones are pendulous (hanging down loosely), with persistent scales (unlike true firs), and are distinct in having a long, tridentine (three-pointed) bract that protrudes above each scale. Douglas-firs support a variety of wildlife both with cover and seeds and are important in watershed protection. Douglas-fir seeds are an important food for small mammals such as mice, voles, shrews and chipmunks. The seeds are also important in the diets of the pine siskin, sparrows, juncos and finches. Douglas-fir needles are a staple in the spring diet of blue grouse.
Douglas-fir is widely used in landscaping. It is planted as a specimen tree or in mass plantings. Douglas-fir’s growth rate is medium. It is the tree most often used for cut Christmas trees. Douglas-fir, like other conifers, are called conifers because they bear their seeds in structures called cones. Cones protect the ovules and seeds, and they facilitate pollination and dispersal.
Douglas-fir can have great longevity, more than 500 years or so, and occasionally up to 1,000 years old. Douglas-fir is a major component of Pacific Northwest old-growth forests and the Rocky Mountains. Wildlife that need old-growth forests include Vaux’s swifts, amphibians, small mammals, woodpeckers and the Northern spotted owl. Douglas-fir can grow under a wide range of climatic conditions. It is very-long lived, tough, and durable.
Douglas-fir represents the climax vegetation in the upper part of the montane zone (pertaining to mountainous regions). Montane zones get colder as the elevation increases. Hence Douglas- fir’s hardiness allows it to survive at these really cold elevations of the montane zone. Douglas-fir’s life form is Phanerophyte: a plant whose buds or shoot apices are borne on aerial shoots (the vegetative means whereby these plants survive periods of unfavorable conditions).