Western red-cedar (RC)

Thuja plicata

Native range

Native to the Pacific north-west of America with a wide range from Alaska to California and also inland to the Cascade Mountains.

Provenance choice

Limited provenance testing suggests that seed sources from western Washington or Vancouver Island should be preferred.

Site requirements

A shade tolerant species with good vigour and volume production, although early growth can be slow. Best suited to more humid regions with an annual rainfall of > 800 mm. Cold hardy throughout Britain, moderately frost tolerant, does not withstand exposure, but is moderately drought tolerant. Vulnerable to fungal attack in nurseries which historically has restricted planting stock availability. Grows best on medium to very rich soils with fresh to moist soil moisture but will tolerate calcareous soils if grown under light shelter. Not suited to very poor and very dry soils but will grow on gleys and occurs on some peat soils in its natural range. Can be grown in mixture with a range of conifer and broadleaved species.

Pests and pathogens

Markedly susceptible to Armillaria (honey fungus) as a cause of decay and death, and to Heterobasidion (Fomes root and butt rot) as a cause of decay. Cypress aphid (Cinara cupressivora) is a not uncommon cause of foliage browning on western red cedar.


Currently a minor species in Britain, but may find an expanded role as a means of diversifying upland conifer forests as an adaptation to projected climate change.