From diminutive bonsai into the soaring “Green Giant,” arborvitae (Thuja spp.) Seem to hold a special place in the hearts of many gardeners. American arborvitae are split between eastern and western species, but homeowners may also like oriental arborvitae (Platycladus orientalis, also known as Thuja orientalis) and Thuja koraiensis, or Korean arborvitae. Arborvitae has flat, scale-like foliage, which is usually a verdant light, medium or dark green, and appealing cones. The plants typically maintain their foliage nearly all the way to the base of the trunk, giving the plants a pristine, compact look. Depending on the species and variety, arborvitae is relatively low maintenance.
Thuja occidentalis, also referred to as Eastern or American arborvitae, grows best in U.S. Department of Agriculture plant hardiness zones 2 through 7, however, a number of the several cultivars are hardy in USDA zones 9 through 11. Western red cedar (Thuja plicata) is also called giant arborvitae and typically thrives in USDA zones 6 through 11, as does oriental arborvitae. Korean arborvitae grows best in USDA zones 5 through 8 and may be expanded as a tall (to 15 feet) tree or a tree up to 30 feet tall. Thuja plicata is the longest-lived tree of this bunch, with specimens over 150 years old, while T. occidentalis and T. orientalis live 50 to 150 decades. T. plicata can also be the tallest arborvitae, growing up to 120 feet at cultivation, while T. occidentalis typically gets to 65 feet tall and T. orientalis a mere 50 feet tall.
Numerous Thuja occidentalis varieties afford homeowners a wide variety of choices in proportion and form. Although the species has a conical form, a few smaller varieties would be globe-shaped, such as “Little Gem,” a hammer which only grows to about 3 feet tall, or “Woodwardii,” which grows into a round, 8-foot-tall tree. Thuja “Green Giant,” suitable to USDA zone 8, forms a 60-foot pyramid at the garden. Thuja orientalis “Aurea Nana” is suitable to USDA zone 9 and forms a 4- to 6-foot-tall world with dense, bright gold leaf. “Emerald” forms a 15-foot-tall pyramid of dense, brilliant green leaf and is suitable to USDA zone 8. If the giant Western arborvitae is too much to your smaller lawn, the diminutive “Pygmaea,” suitable to USDA zone 8, grows only 2 to 3 feet high and has a mounding form.
Arborvitae grow well in loamy soil but will tolerate clay and sandy soils, too. In very hot areas, the plants may have to get some afternoon shade. Otherwise, they could grow in full sunlight to partial shade, in highly acidic to slightly alkaline soil, except for Korean arborvitae, that needs neutral to alkaline soil. Arborvitae are usually slow-growing trees or shrubs that rarely require pruning or fertilizer. They prefer moist soil, so supplemental irrigation during prolonged drought or in very dry areas may be critical.
Arborvitae can suffer from occasional insect infestations such as aphids, scale insects and bark beetles. A number of these may be controlled using a hard spray of water from the garden hose, if needed. Too little or too much water may lead to leaf to disappear as well as the tree to become worried. Deer prefer to snack on arborvitae leaf, however some arborvitae are thought to be resistant. Healthy trees usually withstand insects and problems and recover by themselves.