Thuja occidentalis

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Thuja occidentalis

Thuja occidentalis foliage and cones

Kingdom:	Plantae
Division:	Pinophyta
Class:	Pinopsida
Order:	Pinales
Family:	Cupressaceae
Genus:	Thuja
Species:	T. occidentalis

Binomial name

Thuja occidentalis
L.

Thuja occidentalis is an evergreen coniferous tree, in the cypress family Cupressaceae, which is widely cultivated for use as an ornamental plant. The endemic occurrence of this species is a north-eastern distribution in North America. It is thought to be the first tree of that region to be cultivated in Europe.

1 Description
2 Distribution
3 Naming and taxonomy
4 Ecology
5 Uses
6 References

[edit] Description

An evergreen tree with fan-like branches and scaly leaves. Unlike the closely related species, Thuja plicata (Western Redcedar), it is only a small tree. Growing to a height of 10-20 m tall with a 0.4 m trunk diameter, exceptionally to 30 m tall and 1.6 m diameter, the tree is often stunted or prostrate. The bark is red-brown, furrowed and peels in narrow, longitudinal strips. The foliage forms in flat sprays with scale-like leaves 3-5 mm long. The cones are slender, yellow-green ripening brown, 10-15 mm long and 4-5 mm broad, with 6-8 overlapping scales. The branches may take root if the tree falls.^[1]

Eastern white cedars found to be growing on cliff faces in Southern Ontario are the oldest trees in Eastern North America and all of Canada growing to ages in excess of 1320 years old.^[2]

[edit] Distribution

Native to the northeastern U.S. and southeastern Canada, from central Saskatchewan east to New Brunswick, and south to eastern Tennessee in the Appalachian Mountains.

[edit] Naming and taxonomy

The species was first described by Carolus Linnaeus in 1753, the name remains current. Common names include Eastern Arborvitae, American Arborvitae, Techny Arborvitae, or just Arborvitae, the last particularly in the horticultural trade. This name, arbor vitae, is derived from the tree of life motif - for the supposed medicinal properties of the sap, bark and twigs.^[3] Other names by which it is known include Northern Whitecedar, Eastern Whitecedar or White Cedar, and Swamp Cedar. Thuja occidentalis trees are unrelated to cedars, or to the Australian tree, Melia azedarach, also known as White Cedar. A large number of names for cultivars are used by horticulturalists.

[edit] Ecology

Thuja occidentalis grows naturally in wet forests, being particularly abundant in swamps where other larger and faster-growing trees cannot compete successfully. It also occurs on other sites with reduced tree competition such as cliffs. Although not currently listed as endangered, wild Thuja occidentalis populations are threatened in many areas by the very high deer numbers encouraged by hunting associations; deer find the soft evergreen foliage a very attractive winter food, and strip it rapidly. The largest known is 34 m tall and 175 cm diameter, in South Manitou Island within Leelanau County, Michigan. It can be a very long-lived tree in certain conditions, with notably old specimens growing on cliffs where they are inaccessible to deer and wildfire; the oldest known living specimen is just over 1,000 years old, but a dead specimen with over 1,500 growth rings has been found. These very old trees are, despite their age, small and stunted due to the difficult growing conditions.

[edit] Uses

A trimmed Eastern Arborvitae hedge

Thuja occidentalis is very widely used as an ornamental tree, particularly for screens and hedges. Over 300 cultivars have been selected and named for garden use; some of the commoner in the horticultural trade include 'Degroot's Spire', 'Ellwangeriana', 'Hetz Wintergreen', 'Lutea', 'Rheingold', 'Smaragd' (a.k.a. 'Emerald Green'), 'Techny', and 'Wareana'. It was introduced into Europe as early as 1540 and today is widely cultivated there, especially in parks and cemeteries.

The most prominent commercial uses of northern white cedar are for rustic fencing and posts, along with log cabins, lumber, poles, and shingles.^[4] White cedar is the preferred wood for the structural elements, such as ribs and planking, of birchbark canoes and the planking of wooden canoes.^[5]

The foliage of thuja is rich in Vitamin C and is believed to be the annedda which cured the scurvy of Jacques Cartier and his party in the winter of 1535–1536.^[4] Due to the neurotoxic compound thujone, internal use can be harmful and is not recommended.

The essential oil within the plant has been used for cleansers, disinfectants, hair preparations, insecticides, liniment, room sprays, and soft soaps. There are some reports that the Ojibwa made a soup from the inner bark of the soft twigs. Others have used the twigs to make teas to relieve constipation and headache.^[5]