Thuja plicata Seeds | Western Red Cedar
LATIN NAME: Thuja plicata
COMMON NAME: Western Red Cedar
Plant Profile
Western redcedar is the great aromatic conifer of the Pacific Northwest and one of the longest-lived and most useful trees in North America. It grows from southeast Alaska through British Columbia, Washington, Oregon and Idaho to northern California, mostly in wet coastal forests and river valleys, where it reaches fifty to seventy metres and a trunk two metres or more across. The foliage is made of flat sprays of scale-like leaves, glossy above and marked beneath with white bands of stomata, and it smells of tansy when rubbed. The cones are small, upright and woody, opening to release winged seeds. Old trees become hollow and grotesquely buttressed, and they can live for a thousand years or more. The wood is light, soft and famously resistant to decay, which is why it has been the primary building material of the Northwest Coast for millennia.
Science & Biotechnology
Thuja plicata is a member of the cypress family and one of the few conifers that tolerates deep shade as a seedling, which allows it to regenerate beneath a closed canopy of hemlock and fir. The rot resistance of its heartwood comes not from resin but from tropolone compounds, chiefly beta-thujaplicin, which are toxic to fungi and bacteria and give the wood its characteristic smell. Those compounds are water-soluble, which is why old cedar stumps rot from the inside out over centuries and why the wood weathers to silver-grey. The foliage contains thujone, a monoterpene that is poisonous in quantity and is the reason cedar oil should never be taken internally. The tree is monoecious, with male and female cones on the same individual, and it is wind-pollinated in spring; the cones mature in a single season. Its bark is fibrous and shreds in long strips, an adaptation to fire and to the wet climate it inhabits.
Uses & Benefits
The wood splits straight, weighs little and resists rot, and it has been used for house siding, roof shingles, canoes, totem poles, boxes and fish traps. Northwest Coast peoples used the bark for clothing, baskets, rope and medicine, and the tree sits at the centre of their material culture. In modern construction, cedar is used for cladding, decking, saunas and greenhouses, and the shingles that roofed much of North America came from it. The foliage yields an essential oil used in insect repellents and in perfumery, and the sawdust is used as a mulch and a moth deterrent. In gardens it makes a dense, fast hedge and a good shelterbelt, and there are dozens of cultivars in gold, dwarf and weeping forms. It is also a tree for damp ground and shade, where few conifers will grow.
Growing from Seed
Sow in late winter on the surface of a peaty mix, since the seed needs light, and give it four to six weeks of cold beforehand; germination is good and usually takes three weeks. Keep the seedlings shaded and moist through their first summer, and prick them out into deep pots when they are 5 cm high. Plant out in autumn or early spring, in full sun or partial shade, in any soil that does not dry out completely; the tree tolerates wet ground and even seasonal flooding. Space hedge plants 60 to 90 cm apart and trim in late summer, not in spring, to keep the cut edges tidy. Protect young trees from deer, which browse the foliage hard. The tree is hardy to about minus twenty-five once established, and it grows quickly for a conifer, adding half a metre a year in good conditions.
Our Take
Aromatic, rot-proof and tolerant of shade, with a lifespan measured in centuries. The best conifer for wet ground and for a hedge that lasts.
Related Reading
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