Thuja occidentalis, also known as white cedar, is an evergreen coniferous tree,
in the cypress family Cupressaceae, which is native to eastern Canada and
much of the north, central and upper Northeastern United States, but widely
cultivated as an ornamental plant. The species was first described by Carolus
Linnaeus in 1753, and the binomial name remains current.
Common names Common names include:
The name arborvitae is particularly used in the horticultural trade in the United
States. It is Latin for "tree of life" - due to the supposed medicinal properties
of the sap, bark and twigs. Despite its common names, it does not belong to the
cedar genus, nor is it related to the Australian white cedar, Melia azedarach.
Description T. occidentalis has fan-like branches
and scaly leaves. Unlike the closely related species Thuja plicata, it is
only a small tree, growing to a height of 10–20 metres tall with a 0.4 metres
trunk diameter, exceptionally to 30 metres tall and 1.6 metres 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 millimetres long. The cones are slender, yellow-green ripening
brown, 10–15 millimetres long and 4–5 millimetres broad, with 6-8 overlapping
scales. The branches may take root if the tree falls.
Distribution Thuja occidentalis is native to Manitoba
east throughout the Great Lakes region and into Ontario, Québec, Vermont, New
Hampshire, Maine, Prince Edward Island, New Brunswick, and Nova Scotia. Isolated
populations exist to the south in Massachusetts, Connecticut, Ohio,
Kentucky, Tennessee, North Carolina, Pennsylvania, Maryland, Virginia, and
West Virginia. Ecology
Thuja occidentalis grows naturally in wet forests, being particularly abundant
in coniferous 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 high deer numbers; deer
find the soft evergreen foliage a very attractive winter food, and strip it
rapidly. The largest known specimen is 34 m tall and 175 cm diameter, on South
Manitou Island within Leelanau County, Michigan.
This 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 1,100 years old, but a dead
specimen with over 1,650 growth rings has been found. Despite their age, these
very old trees are small and stunted due to the difficult growing conditions. The
Witch Tree, a T. occidentalis growing out of a cliff face on Lake Superior in
Minnesota, was described by the French explorer Sieur de la Verendrye as being
a mature tree in 1731; it is still alive today.
T. occidentalis specimens found 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 1,653 years. Uses
White cedar is a tree with important uses in traditional Ojibwe culture.
Honored with the name Nookomis Giizhik, the tree is the subject of sacred
legends and is considered a gift to humanity for its myriad uses, among them
crafts, construction, and medicine. It is one of the four plants of the Ojibwe
medicine wheel, associated with the north. The foliage of Thuja occidentalis
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. Due to the presence
of the neurotoxic compound thujone, internal use can be harmful if used for
prolonged periods or while pregnant. Northern white cedar is commercially
used for rustic fencing and posts, lumber, poles, shingles and in the
construction of log cabins. White cedar is the preferred wood for the structural
elements, such as ribs and planking, of birchbark canoes and the planking of
wooden canoes. 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.
In the 19th century, T. occidentalis extract was in common use as an
externally applied tincture or ointment for the treatment of warts, ringworm,
and thrush. "An injection of the tincture into venereal warts is said to
cause them to disappear." Strips of clear, northern whitecedar
wood were used to make the original Au Sable river boats, formerly known as the
"pickup trucks of the Au Sable". The light, rot resistant wood was preferred
but is now commonly replaced by marine grade plywood. Since the plywood is
available in lengths of 8 feet, the modern boats are slightly shorter than
the older boats which were around 25 feet long.
Cultivation T. occidentalis is widely used as an
ornamental tree, particularly for screens and hedges, in gardens, parks
and cemeteries. Over 300 cultivars exist, showing great variation in
colour, shape and size, with some of the more common ones being: 'Degroot's
Spire', 'Ellwangeriana', 'Hetz Wintergreen', 'Lutea', 'Rheingold',
'Smaragd', 'Techny', and 'Wareana'. It was introduced into Europe as early as
1540. The following cultivars have gained the
Royal Horticultural Society's Award of Garden Merit:-
Gallery See also
Cedar wood References
Notes External links
Conifer Specialist Group. Thuja occidentalis. 2006. IUCN Red List of
Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 12 May
2006. Borealforest.org: Thuja occidentalis