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Cupressaceae FAMILY Least Concern

Thuja plicata

Thuja plicata

Edibility
2/5
Medicinal
2/5

Safety & Hazards

The essential oil in this plant contains thujone. Thujone is a GABA receptor antagonist which allows neurons to fire more easily. In larger doses this can cause muscle spasms and convulsions, and can also be toxic to brain, kidney, and liver cells. There has been a lot of negative press regarding thujone, particularly in the mid 19th century when thujone was reported to be more dangerous than alcohol - since shown to be exaggerated; and reports in the 1970’s that it might have a similar effect on the brain to THC (found in cannabis) – since found to be incorrect. Thujone is probably best known for its use in the alcoholic drink ‘Absinthe’. It is also found in the essential oils of many other plants that are used in herbal medicines and foods, including Arborvitae (Thuja species), some Junipers (Juniperus species), Wormwoods (especially Artemisia absinthium) and Sage (Salvia officinalis). There are some legal restrictions in various countries on the quantity of thujone that can be added to foods and drinks and these vary between countries. Side effects from consuming thujone can include sleeplessness and anxiety but, unless the pure essential oil is used, the quantity of thujone found in plants is well within safety levels. Pregnant women, however, may be advised to restrict their use of thujone-containing plants.

Cultivation Details

HabitEvergreen Tree
GrowthFast

Thuja plicata is found in two, more or less disjunct areas, each with their own distinct climate - the Pacific coastal mountains and Rocky Mountains. The Pacific coastal mountains experience high rainfall levels (up to 6,600mm per annum with the majority falling in winter) and mild winters. Here, in the wet forests amongst many other giant species such as the Redwood (Sequoia sempervirens), Thuja plicata can be up to 75 metres tall and live for more than 1,000 years. In the Rocky mountains of the interior, the climate is much drier (rainfall does not exceed 1,200mm per annum), winters are much colder, and the tree is usually less than 50 metres tall[1]. Prefers a moist loamy soil[2, 3]. Dislikes dry soils[4]. Not suitable for light sandy soils because it is shallow rooting[5], but it succeeds on most other soil types, even on waterlogged soils and heavy clays[3, 6]. Succeeds in chalky soils[6]. Prefers some shelter from the wind according to some reports[2, 3] whilst others say that it is fairly wind resistant[4, 5]. Trees tolerate salt winds[5] but not severe maritime exposure[PFAF]. The wood and foliage are highly aromatic[7]. The foliage has a strong fruity smell, like pear-drops or crushed apples[8]. A fast growing tree, it often puts out new growth of 1 metre a year and can average 60cm a year for the first 40 years. Increase in girth can also be rapid, 5cm a year for the first 60 years has been recorded[8]. The tree is sometimes planted for forestry in Britain[9], it is at its best in the moister western half of the country[4, 8]. There are many named varieties selected for their ornamental value[10]. Plants are very tolerant of light trimming, so long as this is not back into old wood. Plants can also retain their lower branches unless these are shaded out by neighbouring plants[4]. The foliage turns bronze in cold weather[3]. Trees are notably susceptible to honey fungus[3, 6]. Western redcedar ( Thuja plicata ) is the provincial tree of British Columbia[11].

Propagation

Seed - best sown when ripe in the autumn in a cold frame[12]. Stored seed germinates best if given a short cold stratification[12]. It can be sown in a cold frame in late winter. When they are large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for their first winter. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts. If growing large quantities of plants, the seed can be sown in an outdoor seed bed in mid spring[13]. Grow the plants on for two years and then plant them out into their permanent positions in late autumn or early spring. Cuttings of half-ripe wood, 5 - 8cm with a heel, mid summer in a shaded frame. Forms roots by the end of September but it should be overwintered in a frame[13]. Cuttings of almost ripe wood, 5 - 10cm with a heel, September in a cold frame. Forms roots in the following summer. Plant out in autumn or spring[13]. Cite as: Temperate Plants Database, Ken Fern. temperate.theferns.info. 2026-02-21. <temperate.theferns.info/plant/Thuja+plicata>

Pollinators

Wind

References

  1. [1]IUCN Red List of Threatened Species — http://www.iucnredlist.org/ ↩︎A list of plants under threat and facing possible extinction, usually with brief details of the threats and information on habitat.
  2. [2]RHS Dictionary of Plants plus Supplement. 1956 — F. Chittendon. · Oxford University Press · 1951 · ISBN - ↩︎Comprehensive listing of species and how to grow them. Somewhat outdated, it has been replaced in 1992 by a new dictionary (see [ 200 ]).
  3. [3]Conifers. — Rushforth. K. · Christopher Helm · 1987 · ISBN 0-7470-2801-X ↩︎Deals with conifers that can be grown outdoors in Britain. Good notes on cultivation and a few bits about plant uses.
  4. [4]Trees and Shrubs Hardy in Great Britain. Vol 1 - 4 and Supplement. — Bean. W. · Murray · 1981 · ISBN - ↩︎A classic with a wealth of information on the plants, but poor on pictures.
  5. [5]Shelter Trees and Hedges. — Rosewarne experimental horticultural station. · Ministry of Agriculture, Fisheries and Food · 1984 · ISBN - ↩︎A small booklet packed with information on trees and shrubs for hedging and shelterbelts in exposed maritime areas.
  6. [6]The New RHS Dictionary of Gardening. 1992. — Huxley. A. · MacMillan Press · 1992 · ISBN 0-333-47494-5 ↩︎Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
  7. [7]Identification Guide to the Trees of Canada — Lauriault. J. · Fitzhenry and Whiteside, Ontario. · 1989 · ISBN 0889025649 ↩︎Very good on identification for non-experts, the book also has a lot of information on plant uses.
  8. [8]Conifers in the British Isles. — Mitchell. A. F. · HMSO · 1975 · ISBN 0-11-710012-9 ↩︎A bit out of date (first published in 1972), but an excellent guide to how well the various species of conifers grow in Britain giving locations of trees.
  9. [9]Flora of the British Isles. — Clapham, Tutin and Warburg. · Cambridge University Press · 1962 · ISBN - ↩︎A very comprehensive flora, the standard reference book but it has no pictures.
  10. [10]The RHS Gardener's Encyclopedia of Plants and Flowers — Brickell. C. · Dorling Kindersley Publishers Ltd. · 1990 · ISBN 0-86318-386-7 ↩︎Excellent range of photographs, some cultivation details but very little information on plant uses.
  11. [11]Flora of N. America — http://flora.huh.harvard.edu/fna/ ↩︎An on-line version of the flora with an excellent description of the plant including a brief mention of plant uses.
  12. [12]The Reference Manual of Woody Plant Propagation. — Dirr. M. A. and Heuser. M. W. · Athens Ga. Varsity Press · 1987 · ISBN 0942375009 ↩︎A very detailed book on propagating trees. Not for the casual reader.
  13. [13]Propagation of Trees, Shrubs and Conifers. — Sheat. W. G. · MacMillan and Co · 1948 · ISBN - ↩︎A bit dated but a good book on propagation techniques with specific details for a wide range of plants.
  14. [14]Vascular Plants of the Pacific Northwest. — Hitchcock. C. L. · University of Washington Press · 1955 · ISBN - ↩︎A standard flora for Western N. America with lots of information on habitat etc. Five large volumes, it is not for the casual reader.
  15. [15]Manual of the Trees of N. America. — Sargent. C. S. · Dover Publications Inc. New York. · 1965 · http://www.biodiversitylibrary.org/ · ISBN 0-486-20278-X ↩︎Two volumes, a comprehensive listing of N. American trees though a bit out of date now. Good details on habitats, some details on plant uses. Not really for the casual reader. It can be downloaded from the internet.
  16. [16]Plants in British Columbian Indian Technology. — Turner. N. J. · British Columbia Provincial Museum · 1979 · ISBN 0-7718-8117-7 ↩︎Excellent and readable guide.
  17. [17]Sturtevant's Edible Plants of the World. — Hedrick. U. P. · Dover Publications · 1972 · ISBN 0-486-20459-6 ↩︎Lots of entries, quite a lot of information in most entries and references.
  18. [18]Tanaka's Cyclopedia of Edible Plants of the World. — Tanaka. T. & Nakao S. · Keigaku Publishing; Tokyo · 1976 · ISBN - ↩︎The most comprehensive list of edible plants I've come across. Only the briefest entry for each species, though, and some of the entries are more than a little dubious. Not for the casual reader.
  19. [19]Food Plants of the N. American Indians. — Yanovsky. E. · U.S. Depf of Agriculture. · ISBN - ↩︎A comprehensive but very terse guide. Not for the casual reader.
  20. [20]Native American Ethnobotany — Moerman. D. · Timber Press. Oregon. · 1998 · ISBN 0-88192-453-9 ↩︎Very comprehensive but terse guide to the native uses of plants. Excellent bibliography, fully referenced to each plant, giving a pathway to further information. Not for the casual reader.
  21. [21]Dictionary of Economic Plants. — Uphof. J. C. Th. · Weinheim · 1959 · ISBN - ↩︎An excellent and very comprehensive guide but it only gives very short descriptions of the uses without any details of how to utilize the plants. Not for the casual reader.
  22. [22]A Dictionary of Plants Used by Man. — Usher. G. · Constable · 1974 · ISBN 0094579202 ↩︎Forget the sexist title, this is one of the best books on the subject. Lists a very extensive range of useful plants from around the world with very brief details of the uses. Not for the casual reader.
  23. [23]Ethnobotany of Western Washington. — Gunther. E. · University of Washington Press · 1981 · ISBN 0-295-95258-X ↩︎A small book, it is a good guide to useful plants in Western N. America.
  24. [24]Economic Botany. — Hill. A. F. · The Maple Press · 1952 · ISBN - ↩︎Not very comprehensive, but it is quite readable and goes into some detail about the plants it does cover.
  25. [25]Plant Fibres for Papermaking. — Bell. L. A. · Liliaceae Press · 1988 · ISBN - ↩︎A good practical section on how to make paper on a small scale plus details of about 75 species (quite a few of them tropical) that can be used.
  26. [PFAF]Plants for a Future — pfaf.org ↩︎