Arborvitae Identification (Thuja occidentalis)

Check Thuja occidentalis for a narrow, dense evergreen form with flattened sprays.

• Leaves are tiny overlapping scales, not needles, pressed tightly to the twigs.
• Branchlets form flat, fanlike sprays arranged mostly in one plane.
• Cones are small, upright to slightly drooping, about 1/2 inch (1 cm) long, with 8 to 12 scales.
• Older trunks often show reddish-brown bark that peels in thin, fibrous strips.

Look at both the flat sprays and the small scaled cones for a quicker visual match.

Thuja occidentalis shows clear age-related shifts in foliage, branching, and cone appearance.

• Seedling: Seedlings first show short needle-like leaves, not flattened sprays. Stems are slender and upright, with a simpler outline than later stages.
• Juvenile plant: Juvenile plants keep more awl-shaped, pointed leaves and irregular branching. The plant stays open in form before the dense, fanlike branchlets dominate.
• Mature plant: Mature Arborvitae carries tightly overlapping scale leaves in flattened vertical sprays. Plants become narrowly conical, sometimes reaching 20-50 feet (6-15 m), with fibrous reddish-brown bark.
• Fruiting stage: Fruiting branches bear many small upright cones, about 1/2 inch (1 cm) long, changing from green to brown among the flattened sprays.

Arborvitae has several well-established forms that are easy to separate by outline and foliage color.

• 'Smaragd': A narrow, dense column, usually 10-15 feet tall (3-4.6 m), with bright emerald-green sprays that hold color well in winter.
• 'Danica': A dwarf globe, often 2-3 feet tall and wide (0.6-0.9 m), with very short, tightly packed green sprays.
• 'Rheingold': A small rounded shrub with fine juvenile foliage; new growth is golden yellow to orange-bronze, especially in cool seasons.
• 'Filiformis': Branches are long, thin, and threadlike, giving a loose, weeping texture instead of the usual flat fan-shaped sprays.
• 'Holmstrup': A compact narrow pyramid, typically 5-10 feet tall (1.5-3 m), with dark green, strongly layered sprays and a tighter outline than the typical form.

Thuja occidentalis stays evergreen, so it does not go bare in winter. In cold weather, the flat sprays often shift from medium green to duller olive or bronze, then return greener in spring. Small upright cones become easiest to notice from late summer into fall, standing above or among the scale-like foliage.

A few conifers are regularly mistaken for arborvitae in landscapes and hedges.

Thuja occidentalis is native to northeastern and north-central North America, from the Canadian Maritimes west through southern Canada to Manitoba, and south into the Great Lakes region and parts of the northeastern United States. In the wild, it is most often found in cool swamps, bog margins, stream edges, and moist limestone woods. Seeing a conifer growing naturally in calcareous wetlands or cedar swamps can help narrow identification.

• Ingestion risk: Thuja occidentalis contains thujone, especially in the foliage and twigs. Ingestion can be harmful to humans and pets.
• Skin contact: The foliage and sap can irritate skin in some people after handling or pruning, causing contact irritation rather than poisoning.