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Thuja occidentalis L. 1753
pronounced: THOO-yuh ocks-ih-den-TAH-liss
(Cupressaceae – the cypress family)
common names: Northern White Cedar, Arborvita
Thuja is derived from the Greek θυια (thuia), a word used by Theophrastus for an African tree with scented wood, probably a juniper or a cedar; occidentalis is Latin, ‘of the west’. The common name ‘arborvita’, widely used in North America, is Latin for ‘tree of life’, due to the wide belief that the sap, bark and twigs have medicinal properties.
This is a dense, conical to narrow-pyramidal (often maturing to broad-pyramidal) evergreen tree, often single-trunked, native to eastern and Central Canada south to northern Illinois, Ohia and New York. There are also scattered populations further south, in the Appalachians to North Carolina. It grows naturally in wet forests, often in coniferous swamps where other larger and faster-growing trees cannot compete successfully. In the wild, mature trees will sometimes reach about 18 m in height, although in cultivation they seldom grow above 9 m. The largest known specimen is 34 m tall, and grows on South Manitou Island, Michigan. Trees can reach an age of 400 years or more. They are widely cultivated as an ornamental. The tree pictured is one of a pair growing on the nature strip by Mandalay Avenue, Nelly Bay. There are over 300 cultivars, showing great variation in colour, shape and size.
The tree may well have been the first that was introduced into Europe from the new world, brought by French explorers to Paris about 1536. A year earlier, a tea prepared from the foliage and bark (now known to be rich in Vitamin C) had saved Jacques Cartier’s crew from scurvy. We now know that it also contains the neurotoxic compound thujone, so internal use can be harmful if used for prolonged periods, or by pregnant women.
The bark is fibrous, red-brown weathering to grey; diamond-shaped patterns are often apparent.The branches are flattened, with the twigs in one plane. The leaves are small and scale-like, and tightly appressed to the branches. The leaves are of two distinct types: the first flat and broad, and the second appearing folded and narrowed.
The tree is monoecious. Male and female cones are so small as frequently to ecape notice. After anthesis, the male cones quickly wither, The female cones persist and eventually grow to about 1 cm long, oblong, borne upright on the branches, developing a few woody scales oppositely arranged, containing seeds in their axils.
In some areas of North America, the species is threatened by high deer numbers. The animals find the soft foliage a very attractive winter food, and strip it rapidly.
The lightweight, eassily split wood was used for canoe frames by native Americans, who also used the shredded outer bark and the soft wood to start fires.
In the 19th century, extracts from the tree parts were in common use as an externally applied tincture or ointment to treat warts, ringworm and thrush.
Information about medicinal qualities of plants, or about their use as medicines, is for interest only, and is not intended to be used as a guide for the treatment of medical conditions.
Photographs taken in Nelly Bay 2015
Page last updated 9th March 2018