Scientific name: Thuja occidentalis Linnaeus 1753

Synonyms: Chamaecyparis boursieri Carrière, Cupressus arborvitae O.Targ.Tozz., Cupressus nobleana (Beissn.) Lavallée, Juniperus ericoides Mast., Retinispora devriesiana Mast., Retinispora dubia Carrière, Retinispora ellwangeriana Carrière, Retinispora glaucescens Hochst. ex Beissn., Retinispora keteleeri Beissn., Retinispora meldensis Carrière, Retinispora nobleana Beissn., Retinispora pygmaea Beissn., Retinispora troubetzkoyana auct., Thuja bodmeri Beissn., Thuja canadensis K.Koch, Thuja caucasica Gordon, Thuja compacta Standish ex Gordon, Thuja devriesiana Carrière, Thuja ellwangeriana Carrière, Thuja ericoides Gordon, Thuja globosa Beissn., Thuja hoveyi Gordon, Thuja minor Carrière, Thuja nana Carrière, Thuja obtusa Moench, Thuja odorata Marshall, Thuja procera Salisb., Thuja recurva Beissn., Thuja recurvata Beissn., Thuja sibirica Gordon, Thuja tatarica Gordon, Thuja theophrasti Nieuwl., Thuja variegata Marshall, Thuja vervaeneana Van Geert ex Gordon

Common names: Northern white-cedar, Arborvitae, Eastern white-cedar, Swamp cedar, White cedar (English), Cèdre blanc, Thuier cèdre (French)

Description

Tree to 20(-38) m tall in favorable sites, dwarfed and slow growing under harsh conditions, with trunk to 1(-1.8) m in diameter. Bark furrowed, fibrous, reddish brown at first, weathering grayish brown peeling, in longitudinal strips, often spiraling around the trunk. Crown narrowly conical, with closely spaced, short, approximately horizontal branches turned up at the ends. Scale leaves (0.5-)1-3(-5) mm long, yellowish green on both surfaces with paler stomatal zones. Facial leaves with a prominent gland on the midline near the tip. Leaves of main branchlets to 9 mm with long tips pressed against the twigs. Pollen cones 1-2 mm long, with two to four pairs of pollen scales, reddish brown. Seed cones (6-)8-10(-14) mm long, with four to six pairs of scales, the middle two (or three) pairs fertile, each scale with a tiny blunt point below the tip. Seeds one or two per scale, 4-7 mm long, including the slightly longer wings, each wing slightly narrower than the body.

Northern white cedar had a great number of medicinal uses, both internal and external, among native peoples within its range. Use of a fragrant decoction to fight fevers, in particular, led to its adoption by early European visitors and setters and the introduction of the tree to Europe by at least 1558, the earliest known. North American tree introduction. During the winter of 1535-1536, Jacques Cartier provided its common name arborvitae (Latin for “tree of life”) when the ravages of scurvy among the men of his Quebec expedition were lessened by the vitamin C in the foliage.

Eastern North America, from Nova Scotia to Manitoba south to North Carolina and Tennessee. Many habitats, from swamps to dry cliff faces, often on calcareous soils;0-900 m.

Conservation Status

Red List Category & Criteria: Least Concern

As Thuja occidentalis is extremely widespread and in some parts of its range increasing by invasion of abandoned farmland, it is assessed as Least Concern. No specific threats have been identified for this species.

After deforestation associated with European migration and farming, this species is now one of the conifers that invades abandoned fields, especially in the NE of the United States.

This species occupies a geographical range touching in the north on the subarctic taiga-tundra interface and in the south, it extends well into the belt of deciduous angiosperm forests. It is therefore associated both with conifers, most common of which are Abies balsamea, Larix laricina in the boreal zone, Picea mariana, Larix laricina and Pinus banksiana in swampy sites, and Pinus strobus and Tsuga canadensis in uplands, and with angiosperms, mainly Populus balsamifera, Ppulus tremuloides, Betula papyrifera, Betula alleghaniensis, Acer rubrum, and Fraxinus nigra in the tree layer and Alnus rugosa, Acer spicatum, Cornus stolonifera, and Vaccinium spp. in the shrub layer. It grows equally well in swamps and on dry ground, but avoids extremes of both habitats; it is often growing abundantly on soils over limestone in upland areas and on alluvial soils with a high organic and mineral content in lowlands (rich fens supporting forest). This species also invades abandoned fields and pastures. The climate is cool to cold temperate and relatively moist, with a short growing season especially in the north of its range.

The rot resistant properties of the wood of this species, known as 'northern white cedar' by lumbermen, make it an excellent timber for outdoor uses. These include rustic fencing, garden gates and sheds, and shingles. Canoes are still made from this wood because of its light weight, as are tubs and barrels. More industrial uses are found in kraft pulp and particleboard. The leaves were traditionally used in Native American medicine to prepare a decoction to suppress fevers and coughs and to cure rheumatism. White cedar was introduced to Britain in 1596 and has been widely planted as a decorative tree. In horticulture there are many cultivars in common use, both tree forms and dwarfed forms. These emphasize shape of crown (while young plants) and color of foliage, the latter with many shades of yellow in the new foliage. Some cultivars retain juvenile leaf shapes for many years looking like needles instead of the normal decussately arranged scales. This species can be used in hedges as it takes clipping well.

This species is well represented in protected areas throughout its range.

References

Farjon, A. (2010). A Handbook of the World's Conifers. Koninklijke Brill, Leiden.
Eckenwalder, J.E. (2009) Conifers of the World: The Complete Reference. Timber Press, Portland.
IUCN Red List of Threatened Species, International Union for Conservation of Nature and Natural Resources. Cambridge, UK /Gland, Switzerland