The Thuja occidentalis plant is a small to medium sized evergreen tree that is commonly known as the Eastern Arborvitae or White cedar. It natively grows in Eastern Canada and North-eastern USA.
Although full grown pure Thuja occidentalis species trees may grow from 20 feet (6 m)up to 50 feet (15 m) in height (depending upon environment) there are numerous dwarf varieties of this conifer available. This means that it can be used as an ornamental plant even in small gardens. For example the cultivar Thuja occidentalis 'Danica' (white cedar 'Danica') has a height and spread of around 20 inches (50 cm).
There are over 300 known cultivars of Thuja occidentalis available. These have a large range of shapes (from conical and narrow pyramid shape to round), leaf color (golden to green), and sizes (dwarf to natural tree).
Thuja occidentalis 'Little Giant' cultivar photograph by F. D. Richards.
This tree typically has a single trunk with a diameter of around 3 feet (90 cm), though some trees can grow twice as thick in the right circumstances. The bark is a reddish-brown and is furrowed in trenches. Bark may turn greyish in more mature trees. Bark sheds off in strips.
Natively the Eastern Arborvitae is found in wet forests and swamps, where they are easily able to out compete other tree larger species of trees. Deer naturally feed on Arborvitae trees in the winter, so don't grow if deer are an issue in your area.
Quick Growing and Care Guide
Scientific name:Thuja occidentalis
Common Name (s): Eastern Arborvitae, Northern White Cedar, Tree of life, American arborvitae, Grandmother Cedar.
Growing Zone (USA / UK Hardiness): 2 to 7 / H7
Life Cycle/Type: Evergreen Conifer
Plant Height: 20 to 50 feet (6 m to 15 m); Cultivars, can be as small as 20 inches (50 cm); medium sized cultivars for the garden tend to be around 8 to 13 feet (2.5 m) in height.
Plant Spread: 10 to 15 feet (3 to 4.5 m); dwarf cultivars 4 to 20 inches (10 to 50 cm); medium sized cultivars 5 to 8 feet (1.5 to 2.5 m).
Blooms: Does not flower
Leaf Foliage Details: Depends on cultivar. Native tree has flattened fan shaped sprays. Needled leaves are pointed and scale like. Aromatic. Dull green-yellow colour.
Cones: Ovoid. green when juvenile; brown when mature. 1/3rd to 1/2 inch (9 to 14 mm) long. 8 seeds per cone.
Best Light Conditions: Full sunlight to partial shade.
Suitable Soil Types: Well drained gives best results, but species is naturally found in wet forests and swamps.
Suitable Soil pH: neutral to alkaline.
Soil Moisture: Medium, Wet
Sowing, planting, and Propagation: Semi-hardwood cuttings in late summer or at the start of autumn. Spacing depends on cultivar, but at least 2 feet (60 cm) for smaller varieties. See plant spread for a better idea of spacing for Eastern Arborvitae cultivars. If growing from seed then place half a dozen cones into a paper bag and leave in a sunny area to dry out. Shake to remove seeds. Sow onto peat moss and cover with a lid. imbibe in the fridge for about 3 months. place tray into sunny part of the garden in spring. Once seedlings have reached about 2.5 inches (7 cm) transfer to final location (dig a hole larger than the root ball, add a thin layer of potting compost, then plant the root ball and compress with top soil. Provide a good watering.
Care:Low maintenance. Extremely cold hardy. Protect from high winds when young. Some cultivars may irritate the skin so wear gloves. Protect from conifer aphids (numerous natural enemies or wash with soapy water) and scale insects (can be biologically controlled with parasitoid wasps, Black ladybird, or removing egg masses).
Best used for: Screening, hedging, ornamental, smaller cultivars in containers, Winter interest, air polluted areas, landscaping.
Miscellaneous: Oldest known tree is about 1050 years old. Genus named after a type of Juniper. Used in traditional medicines by the indigenous people, the Ojibwe. Often used in local construction as lumber, especially for fences and log cabins. Contains essential oils that are used as a tincture, disinfectant, cleanser, and for soap.
Family: Cupressaceae (Cypress family).
Cultivars: Thuja occidentalis 'Holmstrup': Slow growing, medium sized, Rich green foliage; 'Amber Glow': Slow growing, compact, golden-yellow foliage; 'Smaragd'; Slow growing; conical; bright green leaves; 'Danica'; dwarf; bright green sprays tinged with bronze in the winter; 'Degroot's Spire'; dense, conical, yellow-green leaves.