Pseudotsuga menziesii, Douglas fir
A North American conifer with gloriously soft and aromatic needles, ideal for teas and inhalations in respiratory and other complaints.
scientific name Pseudotsuga menziesii (Mirb.) Franco
family Pinaceae
alternate names Oregon pine, false hemlock
parts used Leaves, bark and resin
Douglas fir can be cut back to lower branches when young in a pollard fashion
Description
Douglas fir is a tall conical-shaped evergreen conifer growing fast with a single trunk up to 60m tall (in the UK, larger in the US) and 10m wide. Young trees have smooth grey bark which ages to become thick, corky, deeply ridged and red-brown. Red-brown buds produce fragrant, citrus-like, soft, dark green flat leaves. Female cones, 7-10cm long, are produced from March to May and the cones ripen September to November, hanging from branches and recognisable by their three-pronged bracts (like a mouse’s back legs and tail). Seed is produced from trees of 10 years or older.
Habitat
Douglas fir is found in western North America, from Mexico to the Canadian Rockies, from sea level to mountains. It is widely planted throughout the world as a forestry timber tree, and naturalised in Europe.
Related plants
Although called a fir, the Douglas fir is not part of the Abies genus.
Cultivation and harvest
Cultivation
The Douglas fir does best in full sun and acid, moist, well-drained soil. It will tolerate some shade and the soil can be poor or fertile but it does not tolerate chalky or waterlogged soils. It is cold hardy, to USDA zone 5a (UK zone 7), and can tolerate strong winds. Slow growing when young but can then increase at over 1m per year. Typical of a conifer, pollarding is not feasible, as the main leader should not be stopped, but at Holt Wood we have found that with careful selection of branches it is possible to reduce height and shape the tree.
Pests and diseases
Resistant to honey fungus, young growth can be damaged by late frosts. Fast growth means that branches are liable to break in wind and so this tree is not ideal to plant near buildings and fences.
Propagation
Seed can be sown in the autumn in a cold frame. When seedlings are large enough to handle, prick them out into individual pots and grow them on in light shade in the cold frame for at least their first winter. Plant in permanent positions in late spring or early summer, after the last expected frosts.
Douglas fir leaves have a citrus-like aroma
Harvesting
The leaves can be harvested at any time of year though there is some variation in the essential oil constituents. Analysis of the secondary metabolites in Douglas fir needles found that most terpenes increased significantly in concentration from mid-June to early August.1 The bark can be harvested year round and dried for later use. The green bark of young trees is laden with blisters full of sticky resin, all designed to protect from damage. Take care when handling the trunk or bark as the resin is very sticky.
Therapeutic use
Traditional
Most parts of the Douglas fir were used by Native Americans particularly for coughs, colds and sore throats. The Sinkyone of California made Douglas fir bark tea to ease colds and as a laxative to help stomach ailments. The Shasta in Northern California used Douglas fir resin to poultice cuts. Douglas fir needles were made into tea by Isleta Puebloans in New Mexico to cure rheumatism.2 Young shoots soaked in cold water could be used as a mouthwash or placed in the tips of shoes to prevent perspiration and athlete’s foot.3
Medicinal actions and uses
Douglas fir is anti-inflammatory, expectorant, diuretic, antiseptic, antifungal and antiviral. It provides a remedy for respiratory complaints, and helps to deal with all kinds of infections and inflammations.
Clinical applications and research
Research evidence is remarkably limited. Based on other studies of essential oils in conifers, the active components, such as pinenes4 and terpinolene,5 have been shown to have antimicrobial, antiviral and anti-inflammatory effects.
Sample preparations and dosage
Use 2 tsp of fresh needles per cup of boiling water and steep for 15 minutes, then strain and drink. Inhale an infusion of needles or resin for coughs and colds. The aromatic needles can be infused in oil, honey, vinegar and brandy. A hydrosol can be distilled from the needles and used as an antiseptic wash.
Douglas fir bark
Constituents and commerce
Key constituents
Cones, needles and wood contain monoterpenes (including alpha- and beta-pinenes, sabinene, alpha-terpinolene and alpha-terpineol).6
Commerce
Douglas fir is primarily cultivated for timber, and young trees are sold as Christmas trees.
Safety
No adverse effects are reported. However, the essential oil should not be used internally or around the face and eyes. Data is lacking so avoid use in pregnancy or breastfeeding.
Other uses
A valuable timber tree. Young leaves are rich in vitamin C. Incense and smudge sticks.
1 Zou J and Cates R. (1995) Foliage constituents of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco (Pinaceae)): Their seasonal variation and potential role in Douglas fir resistance and silviculture management. J Chem Ecol 21: 387-402.
2 Anderson MK. (2003) Plant guide: Douglas fir: Pseudotsuga menziesii. United States Department of Agriculture and Natural Resources Conservation Service. Available at: https://plants.usda.gov/plantguide/pdf/cs_psme.pdf (accessed 16 August 2018).
3 Gunther E. (1973) Ethnobotany of Western Washington: The Knowledge and Use of Indigenous Plants by Native Americans, Seattle: University of Washington Press.
4 Kucharska M, Szymańska JA, Wesołowski W, et al. (2018) [Comparison of chemical composition of selected essential oils used in respiratory diseases]. Med Pr 69: 167-178.
5 de Christo Scherer MM, Marques FM, Figueira MM, et al. (2019) Wound healing activity of terpinolene and α-phellandrene by attenuating inflammation and oxidative stress in vitro. J Tissue Viability 28: 94-99.
6 Garcia G, Garcia A, Gibernau M, et al. (2017) Chemical compositions of essential oils of five introduced conifers in Corsica. Nat Prod Res 31: 1697-1703.