Arborvitae: how to identify it and tell the hedge types apart

Eastern and western arborvitae

Two Thuja species are native to North America.

Eastern arborvitae (Thuja occidentalis) is the wild northern white cedar. The Forest Service maps it from the Atlantic coast in Nova Scotia and Maine west to Manitoba and Minnesota, south to central New York and central Michigan, with isolated stands in the Appalachians as far as North Carolina. It grows in swamps, seeps, on cliffs and in old pastures, reaches 35 to 65 feet, and can live more than 400 years; trees on cliffs and bluffs pass 900. In winter its foliage turns bronze (NC State). The Forest Service counts over 100 cultivars of it planted as ornamentals, for privacy screens, windbreaks and snow fences.

Western arborvitae is western redcedar (Thuja plicata), which Penn State calls giant western arborvitae, native to the northwestern United States and western Canada. Virginia Tech gives it yellow-green scales 1/16 to 1/8 inch long, woody cones about 1/2 inch, stringy reddish-brown bark that comes off in long strips, and a height of up to 200 feet. In the East you meet it mostly as a parent of 'Green Giant'.

'Emerald Green', 'Green Giant' and other hedge arborvitae

When an arborvitae is in a row along a fence, the question is usually which cultivar it is. Size, speed and winter color separate the common ones. The rows below come from Penn State Extension and NC State Extension.

'Green Giant' has a story of its own. NC State says it was developed in Denmark in the 1930s and reached the United States in 1967 through the U.S. National Arboretum. Sources disagree on its winter color: NC State says its foliage stays deep green, Penn State says it fades to bronze. A hedge that grew a foot or two in one season is far more likely to be 'Green Giant' than 'Emerald Green'.

Arborvitae vs Leyland cypress, juniper and false cypress

All four are scale-leaved evergreens sold for hedges and screens, and all four belong to the cypress family. Take one spray, look at both sides, and find a cone.

NC State's Leyland cypress page explains its origin, an accidental cross of Monterey cypress and Nootka cypress on Christopher Leyland's property in England, and notes that the foliage can irritate skin. Leyland grows up to 3 feet a year when young and can reach 50 feet in 15 years. For the other cypresses, see the cypress page; for common, Rocky Mountain and other junipers, the juniper page.

Why arborvitae turns brown

Brown arborvitae is one of the most searched questions about the plant. Two causes are normal or weather-related, and you can usually tell them apart by where the brown is.

Seasonal needle drop: brown inside, in autumn. Wisconsin Extension explains that conifers shed their oldest inner foliage after one or more years, and that on arborvitae the old leaves turn brown rather than yellow and often hang on longer than pine needles. Penn State calls browning of the oldest interior branches in autumn normal shedding. The outer, current growth stays green.

Winter burn: brown tips on the sunny side, in early spring. In winter, sun and wind dry the foliage while frozen soil keeps the roots from replacing the water. Wisconsin Extension's winter burn article lists arborvitae, false cypress and juniper among the plants affected, says browning starts at the branch tips and spreads inward, that foliage facing south, southwest or west is most often hit, and that symptoms show as the snow melts. Scratch the bark of a brown branch: if the tissue under it is green, buds may still break into new foliage. NC State adds that dry, exposed, windy sites make winter burn more likely.

Something else. Spots on current-season foliage, webbing, clusters of mined tips or hanging bags point to a fungus or a pest instead: leaf miners, spider mites and bagworms all occur on arborvitae. The tree disease identification guide sorts symptoms by the part of the tree. Tree Identifier's Diagnose tool gives a quick first opinion from one photo, with a severity badge and a dated record you can compare next spring; a large tree near a house or a whole hedge dying is a job for a certified arborist or your state's extension service.

Arborvitae, white cedar and thuja: the names

Arborvitae, northern white cedar, eastern white cedar and American arborvitae all name Thuja occidentalis; the Forest Service also records the Ojibwe name giizhik. "Thuja" is simply the genus name, so "arborvitae vs thuja" is not a comparison: every arborvitae is a thuja. "Western arborvitae" and "giant arborvitae" mean Thuja plicata. Oriental arborvitae, from China and Korea, was once called Thuja orientalis; NC State now lists it as Platycladus orientalis and notes it is often confused with American arborvitae.

Tree Identifier names a tree or shrub from one photo, and northern white cedar and western redcedar are both in its Collection. Photograph a single spray close up, ideally with a cone, rather than the whole sheared hedge.