Arborvitae

Sun

Full sun to partial shade; growth becomes thinner in deep shade.

Water

Keep the root zone evenly moist, especially during establishment and dry summers. Established trees tolerate brief dry spells but struggle with prolonged drought.

Soil

Moist, well-drained loam, including chalky or alkaline soil. Tolerates clay if drainage is adequate; avoid permanently waterlogged or very dry sites.

Height

40-60 ft (12-18 m); many garden cultivars remain much smaller.

Spread

10-15 ft (3-4.5 m); cultivar spread varies considerably.

Foliage

Evergreen. Aromatic, flattened sprays of green, scale-like leaves. Some plants develop bronze or brownish winter colouring that greens up again in spring.

Growth

Slow to moderate, commonly 6-12 in (15-30 cm) a year once established; cultivar and growing conditions affect growth.

Care needed

Medium

• Plant with the root flare at soil level, allowing space for the chosen cultivar's mature width.
• Water deeply during dry weather for the first two growing seasons; check beneath the surface rather than watering by a fixed schedule.
• Spread 2-3 in (5-8 cm) of organic mulch over the root zone, keeping it clear of the trunk.
• Feed lightly in spring only if growth is poor and a soil test indicates a nutrient shortage.
• Water before the ground freezes if autumn has been dry, and protect young plants from deer and drying winter winds.

Pruning. Lightly trim hedges in late spring after the first flush of growth, keeping the base wider than the top. Cut only into leafy growth because bare old wood rarely reshoots; remove dead or broken branches as needed.

Early spring

Inspect for winter damage and remove broken or clearly dead branches.

Spring

Plant new trees while the soil is workable and refresh mulch without covering the trunk.

Late spring

Lightly trim hedges and shaped plants, staying within green foliage.

Summer

Check soil moisture during dry spells and inspect foliage for mites or bagworms where these occur.

Autumn

Water thoroughly during dry weather and fit deer protection before winter browsing begins.

Winter

Gently brush off loose, heavy snow from below; do not strike frozen branches or try to remove bonded ice.

• Plant suitably sized cultivars as evergreen boundary screens, leaving enough room for their mature width.
• Use a clipped hedge to enclose a formal garden or provide a quiet green background for flowering borders.
• Place narrow cultivars beside entrances or at path junctions for vertical emphasis.
• Combine dwarf globe-shaped cultivars with grasses and perennials for year-round structure.

Garden styles it suits: Formal, Traditional, Topiary garden, Green on green, Winter interest and New England.

Plant it with: Hostas, Astilbes, Siberian irises, Panicle hydrangeas, Switchgrass and Purple coneflowers.

Wildlife: Dense branches provide shelter and nesting sites for birds, and small birds eat the seeds. Deer browse the foliage heavily, particularly in winter. It is wind-pollinated rather than a useful nectar source.

• Deer browsing can strip lower foliage permanently. Use a properly installed deer fence or individual guards; repellents need repeated application.
• Bagworms, especially in parts of the United States, can defoliate plants. Remove overwintering bags by hand and treat newly hatched larvae with an appropriately labelled product if needed.
• Spider mites cause fine speckling and dull, bronzed foliage in hot, dry weather. Check for mites, reduce drought stress and use a labelled mite treatment only when necessary.
• Browning can follow drought, winter desiccation or root rot in saturated soil. Check moisture and drainage before watering more; improve drainage or relocate plants where roots stay waterlogged.

Do not allow people, cats, dogs or horses to eat the foliage or young shoots: they contain potentially toxic oils, including thujone. Ingestion may cause digestive upset; larger amounts or concentrated essential oil can cause serious poisoning, including neurological effects. Ordinary garden handling is generally low risk, although sap and foliage can irritate sensitive skin.

• Western red cedar (Thuja plicata)

  Usually has more drooping shoot tips and conspicuous pale markings on the leaf undersides; arborvitae has less strongly marked undersides. Western red cedar also becomes a much larger tree.

• Oriental arborvitae (Platycladus orientalis)

  Its foliage sprays tend to stand vertically, and its young cones are fleshy and blue-green with distinctive horn-like projections. Thuja occidentalis has small, elongated cones with thin, overlapping scales.

Arborvitae means 'tree of life' in Latin, while occidentalis means 'western', referring to its North American origin.

Propagation. Grow the species from seed after cold, moist stratification, although seedlings vary. Root semi-ripe cuttings in late summer to preserve a named cultivar; rooting may take several months.

Accepted botanical name

Thuja occidentalis

In the US and Canada

Native in Canada and the lower 48 states.

Native range

Connecticut, Illinois, Indiana, Kentucky, Maine, Manitoba, Maryland, Masachusettes, Michigan, Minnesota, New Brunswick and New Hampshire.

Measured

Soil pH 5.2 to 7. Average height 1460 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.