Northern White Cedar (Thuja occidentalis)

The Northern white cedar, also known as American arborvitae, Eastern white cedar, arborvitae, or swamp cedar, is an evergreen conifer belonging to the cypress family (Cupressaceae) and the genus Thuja. It is native to eastern North America and is well adapted to cool climates and moist soils. The species is commonly grown in USDA Hardiness Zones 2–7.

Description

Northern white cedar is a medium-sized evergreen tree with a narrow, conical to columnar form. In landscape plantings, trees typically grow 20–40 feet tall with a spread of 10–15 feet, though some cultivated forms reach 50 feet. Exceptional wild specimens have been recorded at 113 feet in height with trunk diameters up to six feet.

The bark is gray to reddish-brown and peels in long, narrow, fibrous vertical strips. Trunks are often tapered, twisted, and multi-stemmed. Leaves are evergreen, scale-like, and pressed tightly to branchlets,  forming flattened sprays.

Flowers and Cones

The species is monoecious, producing male and female cones on the same tree. Male cones release pollen in spring and quickly wither. Female cones mature into small woody cones about ⅓ inch long, ripening in early autumn and releasing tiny winged seeds.

Growth and Lifespan

Growth is generally slow, averaging 1–2 feet per year under favorable conditions. Northern white cedar commonly lives 200–300 years, with some cliff-dwelling individuals exceeding 1,600 years. Foliage remains
evergreen year-round, though winter bronzing may occur.

Roots and Site Preferences

Northern white cedar is adapted to moist habitats such as swamps, fens, and seepage areas. Roots are shallow and wide-spreading, suited to wet soils. The species prefers neutral to alkaline substrates, cool summers, cold winters, and humid conditions.

Native Range

The native range extends across eastern Canada and the northern United States, including Ontario, Manitoba, New England, the Great Lakes region, and parts of the Appalachian Mountains. In Wisconsin, it is most common in the northern half of the state and along Lake Michigan.

Cultivars

More than 300 cultivars have been developed, varying in size, color, and form. Common selections include:

• ‘Smaragd’ (Emerald Green)
• ‘Techny’
• ‘Rheingold’
• ‘Danica’
• ‘Holmstrup’
• ‘Degroot’s Spire’
• ‘Lutea’
• ‘Wareana’

Ecology

Northern white cedar provides important wildlife habitat. Deer, rabbits, and porcupines browse the foliage, while birds roost in dense branches and feed on seeds and insects. The species stabilizes wet soils and defines many rich fen and swamp ecosystems.

Uses

The wood is lightweight, aromatic, and highly rot-resistant, making it valuable for posts, shingles, fencing, canoes, cabins, and outdoor structures. Indigenous peoples used the inner bark and twigs medicinally. In Ojibwe culture, the tree is known as “Nookomis Giizhik” (Grandmother Cedar).

Cultivation

Northern white cedar is widely planted in parks, cemeteries, hedges, and residential landscapes. It performs best in full sun to partial shade with moist, well-drained soils. Hedges are typically spaced 3–4 feet apart. Young trees benefit from mulching and deep watering.

Pests and Diseases

Common pests include bagworms and spider mites, while heavy deer browsing is often the most serious issue. Heartwood rot may occur in older trees. Proper site selection and spacing help maintain vigor.

Conservation Status

Northern white cedar is not invasive and remains widespread, though conservation status varies regionally. In some eastern states it is listed as threatened or endangered, while in Wisconsin it faces regeneration challenges due to deer pressure.