Arborvitae is an evergreen tree or shrub from the Cypress Family.
Sunlight: Full Sun/Part Shade
Growth Rate: Medium
Soil Type: Prefers Moist, Alkaline; Adaptable
Arborvitae (Thuja occidentalis) is found throughout eastern Canada, New England, and the northern states of the Eastern United States. While it is primarily found in Ohio in urban landscapes, where it often thrives in dry, alkaline soils, it occurs in greatest abundance in the wilds of Ohio when found near acidic bogs.
Arborvitae has many alternative common names, including Eastern Arborvitae, American Arborvitae, White Cedar, and Northern White Cedar. Cedar Swamp in Champaign County, Ohio is named after this tree with White Cedar being the common name referred to in this case. As a member of the Cypress Family, it is related to Eastern Redcedar, False Cypress, and other species of Arborvitae.
Arborvitae has scale-like leaves, which along with its twigs form flattened sprays that are soft to the touch, rather than prickly (as in Eastern Redcedar). While Eastern Redcedar prefers warmer (southern) climates, Arborvitae prefers colder (northern) climates, with Ohio in the middle ground between these two in terms of geographic distribution.
Arborvitae is perhaps the most popular evergreen consumed by deer and other mammals during winter, and its evergreen canopy provides cover for mammals and birds year-round. In many parts of Ohio, it is seen as one of the frequent evergreens in cemeteries. When found in the open, non-compact forms may reach 30 feet tall by 10 feet wide.
Planting Requirements: Arborvitae performs best in moist soils of alkaline pH, but is very adaptable to poor soils that are rocky, sterile, dry or wet, and of neutral to acidic pH. It can be planted just about anywhere there is full sun to partial sun, with minimal aftercare. It is found in zones 3 to 7 in full sun to partial sun, but does not thrive in the southern part of its range.
Potential Problems: Arborvitae is the favorite plant of bagworm, and this pest can nearly or completely defoliate trees in the heat of summer. Plants may be coaxed back into health with supplemental water and sprays the following year to reduce the likelihood of a second attack, if the damage is not too severe. Bagworm damage can be minor and cosmetic, or significant and life-threatening to Arborvitae. The cocoons of the bagworm persist throughout the winter and the resulting larvae may re-infest the same and nearby trees the following year if they are not physically removed, or a spray application applied at the appropriate time.
The lower foliage and twigs of Arborvitae can also be significantly sheared back in winter by deer browsing, and the flexibility of the softwood and its strong tendency to be multitrunked make it a prime candidate for snow and ice damage. Otherwise, Arborvitae is a healthy and vigorous shrub and tree.
The miniature leaves of Arborvitae are primarily scale-like, arranged in an overlapping, shingle-like fashion on the twigs. The actual twig color (often hidden by the scales) can be green, yellow, brown, or orange.
The outer twigs and leaves of Arborvitae tend to lie within a vertical plane, and these are called sprays. Mature specimens of Arborvitae are often devoid of branches at their base, but some retain branches and foliage to the ground, even in old age.
Male and female flowers occur on the same plant in Arborvitae, making them monoecious. The male (staminate) flowers are yellow and drop off in spring, but the greenish female flowers become the yellowish fruits that are held upright. These minature cones turn brown and open up to release the seeds, then persist throughout much of the winter.
The thin mature bark of Arborvitae is scaly to stringy and takes on reddish-brown or gray-brown hues with age. Very old specimens may develop flat ridges and intervening furrows.