Thuja (pronounced "thoo-ya" or "thoo-ja") is a genus of coniferous trees in the Cupressaceae (cypress family). There are five species in the genus, two native to North America and three native to eastern Asia.Farjon, A. (2005). Monograph of Cupressaceae and Sciadopitys. Royal Botanic Gardens, Kew. ISBN 1-84246-068-4Gymnosperm Database: ThujaThey are commonly known as arborvitae (from Latin for tree of life) or thujas; some are sometimes colloquially but incorrectly called "cedar" (they are not cedars).Kelsey, H. P., & Dayton, W. A. (1942). Standardized Plant Names, second edition. American Joint Committee on Horticultural Nomenclature. Horace McFarland Company, Harrisburg, Pa.They are evergreen trees growing to 10?60 m tall, with stringy-textured reddish-brown bark. The shoots are flat, with side shoots only in a single plane. The leaves are scale-like 1?10 mm long, except young seedlings in their first year, which have needle-like leaves. The scale leaves are arranged in alternating
Source:
http://en.wikipedia.org/wiki/Arbor Vitae