Thuja occidentalis

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Thuja occidentalis
Thuja occidentalis.jpg
Thuja occidentalis foliage and cones
Conservation status
Scientific classification
Kingdom: Plantae
Division: Pinophyta
Class: Pinopsida
Order: Pinales
Family: Cupressaceae
Genus: Thuja
Species: T. occidentalis
Binomial name
Thuja occidentalis
L.
Thuja occidentalis range map.png
Natural range

Thuja occidentalis is an evergreen coniferous tree, in the cypress family Cupressaceae, which is native to the northeast of the United States and the southeast of Canada, but widely cultivated as an ornamental plant.[1] The species was first described by Carolus Linnaeus in 1753, and the binomial name remains current.

Common names[edit]

Common names include:-

  • white cedar
  • northern white cedar[2]
  • yellow cedar
  • Atlantic white cedar
  • eastern white cedar[2]
  • swamp cedar[3]
  • false white cedar
  • northern whitecedar
  • arborvitae[3]
  • American arborvitae[2]
  • eastern arborvitae[2]

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.[4] Despite its common names, it does not belong to the cedar genus, nor is it related to the Australian white cedar, Melia azedarach.

Description[edit]

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 (33–66 ft) tall with a 0.4 metres (1.3 ft) trunk diameter, exceptionally to 30 metres (98 ft) tall and 1.6 metres (5.2 ft) 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 (0.12–0.20 in) long. The cones are slender, yellow-green ripening brown, 10–15 millimetres (0.39–0.59 in) long and 4–5 millimetres (0.16–0.20 in) broad, with 6-8 overlapping scales. The branches may take root if the tree falls.[5]

Distribution[edit]

Thuja occidentalis is native to Manitoba east throughout the Great Lakes region and into 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.[5]

Ecology[edit]

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.[6] 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 a French explorer as being a mature tree in 1731; it is still alive today.

Botanical illustration from 1913

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.[5]

Uses[edit]

White Cedar is a tree with important uses in traditional Ojibwe culture. Honoured with the name Nookomis Giizhik ("Grandmother Cedar"), 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.[7] It is one of the four plants of the Ojibwe medicine wheel, associated with the south. 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.[8] 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,[8] White cedar is the preferred wood for the structural elements, such as ribs and planking, of birchbark canoes and the planking of wooden canoes.[9] It was used for the original Au Sable riverboats, known as the pickup trucks of the Au Sable River in Michigan. These craft are now made of marine grade plywood and are a little shorter than the originals, which were typically 25 feet long.

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.[9]

Grown as an ornamental specimen, Powsin Botanical Garden, Warsaw, Poland

In the 19th century, Thuja was in common use as an externally applied tincture or ointment for the treatment of warts, ringworm and thrush.[10] "An injection of the tincture into venereal warts is said to cause them to disappear."[11]

Cultivation[edit]

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' (a.k.a. 'Emerald Green'), '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[edit]

References[edit]

Notes

  1. ^ http://www.probertencyclopaedia.com/cgi-bin/res.pl?keyword=Arbor&offset=0
  2. ^ a b c d "The Gymnosperm Database". 
  3. ^ a b "USDA GRIN Taxonomy". 
  4. ^ Thuja, American Cancer Society, last revised 6/19/2007. available online
  5. ^ a b c "Thuja occidentalis Linnaeus 1753". conifers.org. Gymnosperm Database. 
  6. ^ "Eastern OLDLIST a database of ancient trees and their ages". Rocky Mountain Tree-Ring Research, Inc. & Eastern Kentucky University. 2008. Retrieved 22 August 2013. 
  7. ^ Geniusz, Wendy Makoons (2009). Our Knowledge is not Primitive. Syracuse, NY: Syracuse University Press
  8. ^ a b Russell M. Burns and Barbara H. Honkala (Technical Coordinators) (December 1990). "Thuja occidentalis L.: Northern White-Cedar". Silvics of North America (Agriculture Handbook 654). 
  9. ^ a b "USDA/NRCS Plant Guide: Northern White Cedar, Thuja occidentalis L." (PDF). United States Department of Agriculture. Retrieved 2008-02-15. 
  10. ^ David Hoffmann, Medical Herbalism: Principles and Practices, Healing Arts Press, 2003, p.588
  11. ^ M Grieve, A Modern Herbal, London: Jonathan Cape, 1931, p.177
  12. ^ "RHS Plant Selector - Thuja occidentalis 'Danica'". Retrieved 6 June 2013. 
  13. ^ "RHS Plant Selector - Thuja occidentalis 'Holmstrup'". Retrieved 6 June 2013. 
  14. ^ "RHS Plant Selector - Thuja occidentalis 'Rheingold'". Retrieved 6 June 2013. 
  15. ^ "RHS Plant Selector - Thuja occidentalis 'Smaragd'". Retrieved 6 June 2013. 

External links[edit]