Arborvitae is the common name for evergreen coniferous trees and shrubs belonging to the genus Thuja, part of the cypress family (Cupressaceae). The term, meaning “Tree of Life” in Latin, stems from the discovery of the foliage’s high Vitamin C content, which was used by Indigenous peoples and early French explorers to treat scurvy in the 16th century. The five recognized species within the genus exhibit a naturally disjunct distribution, meaning their native habitats are geographically separated into two distinct regions: North America and East Asia. Two species originate in the Western Hemisphere and three originate in the Eastern Hemisphere.
The North American Native Species
North America hosts two species of Thuja, each occupying a distinct range. The first is Thuja occidentalis, commonly known as Eastern Arborvitae or Northern White Cedar, which has an extensive range primarily centered around the Great Lakes region and northeastern North America. Its native distribution extends westward from the Gulf of St. Lawrence and Nova Scotia through southeastern Canada and the northeastern United States, including states like New York, Michigan, and Wisconsin. Disjunct populations also occur further south along the Appalachian Mountains, reaching as far as western North Carolina and eastern Tennessee.
The second native North American species is Thuja plicata, widely known as Western Red Cedar or Giant Arborvitae, which is found exclusively in the Pacific Northwest. This species thrives in the region’s wet, maritime climate, with its range stretching along the coast from Southern Alaska down to Northern California. It also extends inland through the Cascade Mountains, central British Columbia, northern Idaho, and western Montana, typically occupying moist forest areas and valley bottoms. T. plicata is notably the largest of the Thuja species.
The East Asian Native Species
The Eastern Hemisphere is home to the remaining two widely recognized species of Thuja, which are found in East Asia. Thuja standishii, or Japanese Arborvitae, is native to the mountainous regions of southern Japan, specifically the islands of Honshū and Shikoku. This species is typically a minor component of mixed montane conifer forests, often restricted to moist, rocky precipices at elevations between 500 and 2,000 meters. The native environment of T. standishii is characterized by a cool, temperate climate with high atmospheric moisture.
The other primary East Asian species is Thuja koraiensis, known as Korean Arborvitae, which is indigenous to the Korean Peninsula and a small area in the extreme northeast of China near Changbaishan. This species is a small tree or large shrub that grows in mountain valleys, slopes, and ridges. It is occasionally cultivated for the striking contrast of its foliage, which is dark green on the upper surface but features vivid white stomatal bands on the underside. Separately, the plant often sold as “Oriental Arborvitae” (Thuja orientalis) is not a true Thuja but belongs to the distinct genus Platycladus.
How Native Range Affects Cultivation
The natural habitat of each Thuja species dictates the conditions necessary for its successful growth in a cultivated landscape. Thuja occidentalis, for example, evolved in a region with cold winters and abundant moisture, often growing naturally in swamps and wet sites. It performs best in moist, well-drained soils that are neutral to alkaline and requires consistent water, particularly in warmer climates. This makes it a reliable choice for cold regions in USDA Zones 2 through 7.
In contrast, Thuja plicata is adapted to the Pacific Northwest’s temperate rainforests, preferring cool summers and high humidity. While it also requires moist, fertile soil, it struggles in hot, dry conditions and is intolerant of drought. Its placement in a garden must account for full sun exposure balanced with afternoon shade in hot areas. Conversely, Platycladus orientalis, which originated in more arid parts of China, is more tolerant of dry soils and warmer conditions, making it a better choice for landscapes prone to drought.