Douglas fir

Family

Pinaceae

Habit

Tree

Height

72.5 m

Spread

20 m

Growth

very fast

Lifespan

1300 years

First yield

after 12 years

Hardiness

zone 4–7

Shade tolerance

full sun

Soil

Sand, Silt, Loam

Soil moisture

semi-dry – very wet

pH

5 – 7

Synonyms

Abies douglasii, Douglasie

Times apply to the northern hemisphere in a temperate climate and shift with altitude and cultivar.

Edible: Douglas fir is no fruit tree, but it does supply a well-known flavouring and tea. The young, pale green shoot tips of the May flush taste resinous and lemony and are used fresh as a seasoning in cooked dishes, preserved in sugar, boiled into syrup or used to flavour vinegar and spirits; crushed, they give off the characteristic sweet, fruity scent that distinguishes the species from spruce. Young needles and shoot tips make a refreshing tea rich in vitamin C — a traditional winter drink in North America. Resin exuding from the trunk was used as a chewing gum by various indigenous peoples of North America. The quantities involved are small in every case, and harvesting is confined to young shoots the tree can spare.

Medicinal: Douglas fir was commonly used for medicinal purposes by various Native American tribes to treat a range of ailments. In modern herbal medicine, it is rarely utilized. An antiseptic resin is extracted from the bark and applied as a poultice to treat cuts, burns, wounds, and skin conditions. This poultice is also used for treating injured or dislocated bones. The resin is employed for cough treatment and can be chewed to alleviate sore throats. An infusion made from the green bark was historically used to address excessive menstruation, intestinal bleeding, and stomach issues. A leaf infusion served as a wash and sweat bath for rheumatic and paralyzed joints. Infusions from young shoots were used to treat colds. Branch or shoot infusions were employed for kidney and bladder problems. A decoction from the buds was utilized for treating sexually transmitted diseases. Young shoots were placed in shoe tips to prevent foot sweating and fungal infections. Soaking the shoots in cold water produces a mouthwash.

Other uses: Douglas fir is one of the most important timber trees worldwide. Its wood is heavy, strong, fine-fibred and durable, dries quickly, shrinks little and works well; it is used for load-bearing structures, glulam, windows, poles, furniture and exterior joinery. In Germany average increment runs to almost 19 cubic metres per hectare and year, above that of any native conifer, which makes it the most debated species in forest conversion. The bark is rich in tannin, contains pitch, burns hot and smokelessly and is used as mulch and cork substitute; trunk resin yields adhesives and fixatives. As a fast-growing, comparatively storm-firm tree it is planted in shelterbelts, and its firm needle retention and scent make it one of the most sought-after Christmas tree species.

Site: The first decision is made at purchase, not in the garden — only coastal provenances from Oregon, Washington and southwest British Columbia are proven in Central Europe; interior provenances flush earlier and are killed by frost. The second decision concerns size: Douglas fir reaches 40 to 60 metres and is a tree for forest and park, not for a domestic garden. Above about 30 metres, free-standing specimens in exposed positions regularly lose their crowns; beneath the canopy vigorous surface roots compete with everything growing below. Waterlogged, boggy and flood-prone sites are unsuitable, as are shallow dry ones and strongly calcareous soils. A conservation point to note: the German Federal Agency for Nature Conservation has listed the species since 2013 as invasive, because on dry and acid soils it can displace native vegetation, and recommends a minimum of 300 metres from sensitive habitat types. Forest science disputes this classification, and in Bavaria no invasive spread was found. Care: Plant small, between 30 and 90 centimetres tall. Larger trees break their deep roots on transplanting, stall for years and stay prone to windthrow. Douglas fir grows slowly for the first few years and fast thereafter, with annual shoots of over a metre. The most important protection is against deer: browsing and bark-stripping are the main problem until about the fifteenth year, and individual guards or a fence are essential where deer are numerous. Late frosts damage young growth, so a site without cold-air pooling pays off. On the fungal side there are the two needle casts, Rhabdocline pseudotsugae and Phaeocryptopus gaeumannii, showing as discoloration and periodic needle loss, both avoided by an airy position and the right provenance. Added to these are the Douglas fir woolly adelgid, the seed chalcid and, since 2015, gall midges. Against honey fungus the species is comparatively resistant. No pruning is needed; Douglas fir builds its own crown.

Douglas fir is propagated from seed, and the decisive question is not technique but provenance: only coastal provenances from Oregon, Washington and southwest British Columbia are worth growing in Central Europe. In Germany forest reproductive material is accordingly governed by the Forest Reproductive Material Act — a certificate of origin belongs with any purchase, or you are buying the risk along with the seed. Seed is stratified cold and moist for three to four weeks before sowing and sown shallowly in spring; it germinates promptly and reliably. Watch for the Douglas fir seed chalcid, which eats the seeds out from within and devalues whole batches with nothing to show on the outside. Cuttings root poorly in this genus and come into question only for ornamental forms, which are usually grafted onto seedling stocks. Plant small, between 30 and 90 centimetres, because larger plants lose their deep roots on transplanting and stall for years.

Douglas fir's wildlife value differs sharply between its homeland and Central Europe. In North America some 140 herbivorous species feed on it, its seeds are an important food source for small mammals and birds, and the red tree vole lives almost exclusively in Douglas fir crowns. In Central Europe the association is weaker: 24 bark beetle and 14 longhorn beetle species have been recorded so far, while specialised conifer arthropods colonise it far less readily than native conifers — though more European species move in the longer it is grown here. Its real contribution lies elsewhere: as an evergreen with dense foliage it offers cover, roosting and shelter from wind all year round, at a season when broadleaves stand bare; wood pigeons, thrushes and tits use it regularly for roosting and nesting. Old trees with coarsely fissured trunks and deadwood provide nest and hiding places, and the seeds are taken by crossbills, tits and squirrels. Anyone planting it should know the conservation caveat: on dry and acid soils it can displace native vegetation.

Special: Needles strongly lemon-fruity when crushed -> reliable way to tell it from spruce; cones hanging, with three-pointed bracts protruding ("mouse tails"), unique among the conifers grown here; only coastal provenances worth planting, certificate of origin required under the Forest Reproductive Material Act; increment ~19 cubic metres/ha/year, higher than any native conifer; mature bark up to 30cm thick, insulating against forest-fire heat; lifespan 400-1400years, over 60m in Europe; on the German Federal Agency for Nature Conservation blacklist since 2013, disputed in forestry;

Western North America. The range falls into two forms with markedly different requirements: coastal Douglas fir (var. menziesii) runs from southeast Alaska through British Columbia, Washington and Oregon into California, growing there in a mild, high-rainfall maritime climate. Interior or Rocky Mountain Douglas fir (var. glauca) occupies the Rockies south to central Mexico, where it manages on far less rainfall. The distinction is decisive for European planting: what has proved itself in Germany are coastal provenances from west of the Cascade crest in Oregon, Washington and southwestern British Columbia, up to about 600 metres elevation. In Germany Douglas fir now covers some 218,000 hectares, a good two per cent of the forest area, concentrated in Rhineland-Palatinate and Baden-Württemberg.

In its homeland Douglas fir occupies an extraordinarily wide spectrum, from very wet lowlands with over 2,000 millimetres of annual rainfall to dry mountain sites with 540 millimetres and above 2,000 metres elevation. Its growth optima are narrower: it performs best on deep, loose and fresh loams with medium nutrient and base supply, favoured by mild winters, moderately warm summers and a long growing season. In its moisture requirements it sits between spruce and pine and withstands partial rainfall shortage during the growing season even on dry sites. Against oxygen shortage in the soil, by contrast, it is as sensitive as spruce and tolerates no flooding. Unlike spruce it does not acidify the soil. It forms a heart-root system, exceeds 60 metres in Europe and can live more than a thousand years.