乔木，在原产地高达20，米;树皮红褐色或桔红色，稀呈灰褐色，纵裂成条状块片脱落;枝条开展，树冠塔形;当年生小枝扁，2-3年后逐渐变成圆柱形。叶鳞形，先端尖，小枝上面的叶绿色或深绿色，下面的叶灰绿色或淡黄绿色，中央之叶楔状菱形或斜方形，长1.5-3毫米，宽1.2-2毫米，尖头下方有透明隆起的圆形腺点，主枝上鳞叶的腺点较侧枝的为大，两侧的叶船形，叶缘瓦覆于中央叶的边缘，常较中央的叶稍短或等长，北美香柏尖头内弯。球果幼时直立，绿色，后呈黄绿色、淡黄色或黄褐色，成熟时淡红褐色，向下弯垂，长椭圆形，长8-13毫米，径6-10毫米;种鳞通常5对，稀4对，薄木质，靠近顶端有突起的尖头，下部2-3对种鳞能育，卵状椭圆形或宽椭圆形，各有1-2粒种子，上部2对不育，常呈条形，最上一对的中下部常结合而生;种子扁，两侧具翅。
Common names include:
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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.[3] Despite its common names, it does not belong to the cedargenus, nor is it related to the Australian white cedar, Melia azedarach.
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. Thecones 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.[4]
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.[4]
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 (112 ft) tall and 175 cm (69 in) 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.[5] 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 explorerSieur 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.[4]
White cedar is a tree with important uses in traditional Ojibwe culture. Honored 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.[6] 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.[7]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.[7]White cedar is the preferred wood for the structural elements, such as ribs and planking, of birchbark canoes and the planking of wooden canoes.[8]
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.[8]
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.[9] "An injection of the tincture into venereal warts is said to cause them to disappear."[10]
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.
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:-
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