arborvitae (är´bərvī´tē) [Lat.,=tree of life], aromatic evergreen tree of the genus Thuja of the family Cupressaceae (cypress family), with scalelike leaves borne on flattened branchlets of a fanlike appearance and with very small cones. Some of the numerous cultivated varieties are dwarf forms. There are several species, two native to North America, the remainder native to Asia but sometimes cultivated in the United States. T. occidentalis, of E North America, called arborvitae, white cedar, or Northern white cedar, has many garden forms and is popular for hedges. The leaves were once used as a remedy for rheumatism, and their oil as a vermifuge. T. plicata of W North America, called giant arborvitae, red cedar, or Western red cedar, is much larger and considerably more important as lumber; it is primarily used for making shingles and shakes. The wood of both of these species is soft but quite resistant to decay, hence its popularity for fence posts. Arborvitaes are classified in the division Pinophyta, class Pinopsida, order Coniferales.