Gerald L. Klingaman
Family
Cupressaceae
Botanical Name
Thuja
Plant Common Name
Arborvitae, Thuja
General Description
Arborvitae are evergreen trees of various sizes. They have long been used as landscape specimens and for their soft, rot-resistant wood. There are 5 species in genus Thuja, which are native to North America and east Asia.
These evergreen trees are small to large. The trunks and stems of mature specimens are covered with stringy red-brown bark. The branches are arranged in flattened planes and are covered with leaves that look like scale-like flatten fans. Thuja reproduce through separate male and female cones borne on the same plant. The male pollen cones are small, oval and produce lots of yellow pollen, which is dispersed by the wind to pollinate the female cones. The seed-bearing female cones are variously shaped, scaly and produced at the ends of the branches. They persist on the branches through winter and contain winged seeds that are caught by the wind as the cones open.
The most commonly planted arborvitae is Thuja occidentalis. It is native to eastern North America and is hardy pyramidal coniferous tree. The leaves emit a pungent odor when bruised and its dense branches often curve upwards. Thuja plicata, a native of northwestern North America, is a broadly pyramidal evergreen tree with slender drooping branches. It has feathery flat sprays of dark green, scale-like leaves which emit a fruity odor when bruised. There are also hundreds of cultivated varieties to choose from that come in all forms and sizes.
Generally, Thuja prefer full sun and fertile, acid to alkaline soils with average to good drainage. They are drought tolerant once established but look best with occasional applications of water during the driest times. Newly planted specimens take a while to establish and must be well irrigated or they will die. Typically, these trees are long-lived and become very large, though compact and dwarf cultivars are available. They make great specimen plants, hedges and screens.
