Thuja occidentalis Seeds | Northern White-cedar
LATIN NAME: Thuja occidentalis
COMMON NAME: Northern White-cedar, Eastern Arborvitae, American Arborvitae
Plant Profile
Northern white-cedar is a conifer of ten to twenty metres with flattened sprays of scale-like leaves, a fibrous reddish bark and a narrow, often irregular crown. The foliage turns a dull bronze in winter, which is one reason it reads as a dead tree in a cold February.
It grows in swamps and on limestone cliffs from Manitoba to Nova Scotia, and it is one of the few conifers that tolerates standing water and shallow soil over rock. In a cedar swamp the trees are often the same age, because they all established after a single disturbance. The foliage is aromatic when crushed, and the flat sprays are arranged in vertical planes, which is the mark of the genus.
Science & Biotechnology
The wood is unusually durable in contact with soil, and the heartwood resists decay for decades. The cause is a group of tropolone compounds, the thujaplicins, which are toxic to fungi and are also the reason the timber has a distinctive smell when it is cut.
The leaf oil is rich in alpha-thujone, a monoterpene ketone that acts on the same receptor as camphor and can cause convulsions in overdose. Absinthe and cedar-leaf tea both owe their reputation to this compound, and the oil should never be taken internally. Deer browse the foliage heavily in winter, which is why wild regeneration is often confined to ledges the animals cannot reach. The tree also grows slowly and can live for four hundred years, which is why a cedar swamp is treated as old growth even when the trees in it are small.
Uses & Benefits
The wood splits straight and lasts in the ground, so it goes into fence posts, shingles, boat ribs and canoe gunwales. In the north-east it was the main material for the frames of birchbark canoes, and the bark was used for cordage and for roofing.
The tree is planted as a hedge and as a specimen in gardens, and several hundred cultivars are in the trade, from dwarf globes to golden columns. The foliage is also used in winter arrangements and the oil in small quantities in perfumery, where the thujone content is regulated.
Growing from Seed
Sow seed in autumn and leave the pot outdoors, since the seed needs cold moisture and germinates in spring at a low percentage. Stratify for sixty days at four degrees for a more even stand, and surface sow, since light helps.
Plant out in a position with sun and moist soil, and water through the first two summers. The tree tolerates clay and limestone but not drought, and it is shallow-rooted enough to be lifted by wind on a wet site. Shear hedges in late June, since cutting into old wood leaves a bare patch that does not regrow.
Our Take
The best native conifer for wet ground and for a clipped hedge, and a tree with real durability in the wood. Keep the oil away from children.
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