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Arborvitae is the common name for a genus consisting of coniferous trees, also known as thujas. The genus is made up of five different species of arborvitae, two in North America and three in Eastern Asia. Some of these species are called cedars, but since they aren’t true cedars, they are more properly called red cedars or white cedars. The five species of arborvitae are Korean thuja, Northern white cedar, Western red cedar, Japanese thuja, and Sichuan thuja.
Arborvitae are evergreen, meaning their leaves stay green year-round. They can grow between 10 and 60 meters (32-196 feet) high and have stringy brownish-red bark. Adult arborvitae have scale-like, flat leaves that grow between one and ten millimeters long. Younger seedlings have needle leaves, similar to pine trees. Their cones can grow between one and two centimeters long after six to eight months, with six to twelve scales, each bearing between one and two seeds.
Pollen cones come with between two and six pairs of pollen filled sacks called sporophylls. Seed cones are between 9 and 14 millimeters (0.3 to 0.5 inches) long, are ellipsoid, and will mature during the first year of growth. Only the central most scales of the cone are fertile, and these scales can produce between one and three seeds each. Seeds produce two cotyledons, and are cone shaped. The seeds also have wings, which catch the wind and can send them great distances.
All species of arborvitae are primary food sources for moth larvae and leafminers. High populations of deer can be detrimental to the growing cycle of young arborvitae. They are known to strip seedlings bare of any leaves, which usually results in the death of the tree.
Oil from the arborvitae tree contains a terpene called thujone. Thujone is a potentially lethal aminobutyric acid that damages nerves and can cause hypertonia of affected muscles. Arborvitae are commonly grown ornamentally as trees and in the form of hedges. A hybrid of the Japanese Thuja and the Western red cedar, called the thuja "Green Giant" is especially adept as a hedge and can grow up to 80 centimeters (31.5 inches) per year.
The wood from an arborvitae is soft, light and very aromatic. It is especially resistant to rot and can be easily split. The wood from the Western red cedar is often used for making guitar soundboards. They are known for creating chests that are moth resistant, as well as for making fence posts.
Arborivitaes in our front porch have some brown leaves. Why? Thanks.