What is a Douglas fir

Pseudotsuga menziesii
The Douglas fir

(Photo: G. Brehm)

Their home is North America, but Douglas fir has also been used successfully in forestry as a mixed tree species in Germany for more than 150 years. If it is brought in according to the location and treated correctly in terms of silviculture, the forest owner can expect good yields with a comparatively low operational risk. This makes the Douglas fir the most important non-native tree species in German forestry.

There are two variations of Douglas fir with differing properties. The "green Douglas fir" (also coastal Douglas fir, var. Menziesii) and the "gray Douglas fir" (also domestic Douglas fir, var. Glauca). Cultivation trials have shown beyond any doubt that the "Green Douglas fir" is much more vigorous and less susceptible to diseases than the "Gray Douglas fir" under our climatic conditions.

Douglas fir needles are green and soft. They do not sting and have an intense orange scent. The rather small cones can be seen in Douglas firs that are around 15 years old. However, mast years are rare and only occur about every seven years. The heavily furrowed, thick bark of older Douglas firs has distinctive yellow cork layers. Douglas firs usually anchor themselves well in the forest floor with a deep heart root system.

Claims of Douglas fir

The Douglas fir is relatively tolerant of the demands on soil and climate. It gets along much better than the spruce, especially on poorer sandy soils and is superior to the pine in terms of growth performance. However, it does not like free lime in the topsoil. It cannot take stable roots even on wet locations.
The requirements in detail
  • light
    • shade-tolerant in the youth phase
    • later higher light requirements
  • water
    • adequate water supply
    • no waterlogging
    • very sensitive to drought in youth
  • ground
    • not very demanding in terms of nutrient supply
    • Lime soils shouldn't have lime in the topsoil
    • deep and well ventilated
    • Superficial acidification and soil wounding are beneficial for establishing natural regeneration
  • climate
    • cool, humid climate without major dry periods

Douglas firs in the forest
(Photo: G. Brehm)

Branch of a Douglas fir
(Photo: G. Aas)

Cones and flowers
the Douglas fir
(Photo: G. Aas)

Douglas fir bark
(Photo: G. Brehm)

Silviculture

The green Douglas fir is mainly cultivated in Bavaria. Due to the shade tolerance in the youth, it is well suited for rejuvenation under an umbrella. When planting, it is essential to pay attention to the freshness of the plants, as they are sensitive to drying of the roots. In general, the Douglas fir should not be cultivated in pure stands.

For economic (risk diversification) and ecological (biodiversity) reasons, it should rather be brought in as a mixed tree species together with hardwood. The Douglas fir differentiates itself very well, especially under umbrella, and only needs little care until it is young. If necessary, it can be useful to remove pre-growths and coarse forms. A knot to produce knot-free wood is basically possible.
As the most important non-indigenous tree species, the Douglas fir is particularly in focus. As convinced as many forest owners are of this tree species in the Bavarian forests, it is viewed with skepticism by some nature conservation representatives. The ecological effects of Douglas fir cultivation in Bavarian forests have been the subject of some research work (for example: BMBF-Projekt Mittelschwaben, 2002).

In summary, it can be stated that the Douglas fir is an economically interesting and ecologically unproblematic mixed tree species in suitable areas. Large areas of pure Douglas fir should be avoided.

Dangers to the Douglas fir

As a non-indigenous tree species, the Douglas fir is currently comparatively little threatened by harmful organisms in Bavaria. Book printers and engravers as well as the furrowed spruce bark beetle can occur, but these have so far been of little significance on the Douglas fir. However, two diseases caused by fungi already play a role today (sooty and rusty Douglas fir chutes). But they are a serious problem, especially with the little-grown inland Douglas fir.

If the Douglas fir is to be grown without protective measures, adapted hoofed game populations are an indispensable prerequisite. The Douglas fir is particularly endangered by blow and swept damage from red deer and roe deer.

Threats to the forest and possible damage

Climate outlook

In addition to the local tree species, the Douglas fir is an important mixed tree species in climate change in suitable locations. It is to be expected that their importance will therefore continue to grow.

The forest in times of climate change

Use of wood

The wood of the Douglas fir is sought after and is well paid for. Construction timber made from Douglas fir is used in residential buildings as well as in larger buildings. Compared to spruce, the heartwood of Douglas fir is more durable and weatherproof. It is therefore often used for balconies, windows, doors or constructions outdoors. Knot-free, valuable Douglas fir wood is in high demand for tenders.

The wood market - from regional to global

The tree is named after the Scottish botanist David Douglas. He also brought other important forest species from North America to Europe.

The tallest tree in Bavaria is a Douglas fir. It is located in the Heigenbr├╝cken forestry company in the North Spessart and measures over 60 meters.

A schnapps is distilled from the fresh buds of the Douglas fir.

If you rub the needles of the Douglas fir in your fingers, it smells slightly of citrus fruits.

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