A varied group of attractive, large and small evergreen conifers, mainly conical in habit. Suitable for small or large gardens, depending on variety. Slow growing forms make fine specimen trees.
Family: Cupressaceae (cypress family)
Botanical Name: Thuja
Common Names: Western red cedar, white cedar, British Columbia cedar, arbor-vitae, yellow cypress
Foliage: Evergreen, aromatic, tiny, glossy scale-like leaves.
Cones: Small brown knobbly cones.
Soil: Moist but well-drained or well–drained soil (chalk, clay, sand or loam). Acid, alkaline or neutral pH.
Conditions: Full sun or partial shade, in any aspect.
Habit: Columnar, upright.
Type: Tree or shrub.
Origin: North America, China and Japan.
Toxicity: Harmful if eaten, skin irritant.
Hardiness: Fully hardy in the UK.
Best planted in autumn or spring. Thives in any in moist but well-drained soil. Plant container grown plants in a soil-based compost such as John Innes No. 3. Sap can irritate skin so wear gloves when handling.
Green forms can be planted in partial shade. Golden and variegated forms should be grown in a sunny place to ensure the foliage colours up well. Tall species can be used for hedging or screening. Compact varieties are good for containers, heather gardens, sunny borders, raised beds and the rock garden.
Water well in dry weather. Protect from drying winds.
Pruning is not necessary, except to cut out any reverted variegated shoots as soon as they are detected. Trim hedges in September.
Prone to attack by scale insects and conifer aphid. Can be affected by honey fungus and thuja blight.
Sow seeds in February in a cold frame. Alternatively, take semi-hardwood cuttings of named varieties in autumn and root in a shaded frame.
Thuja koraiensis (Korean arbor-vitae) forms a dense, bushy shrub or narrowly conical, slow growing tree with dark green aromatic foliage. Eventual height to 30ft (10m).
Thuja occidentalis (White cedar) is a slow-growing compact, columnar conifer with deep golden foliage that eventually makes a large shrub. Height to 10ft (3m) or more. Cultivars include:
Thuja orientalis (Chinese arbor-vitae) has flattened sprays of mid-green foliage. Pale brown cones. Height to 15ft (4.5m), spread to 10ft (3m). A number of good dwarf varieties are available, including:
Thuja plicata (western red cedar) is a fast growing long-lived conifer of erect conical habit. Cinnamon-red peeling bark and spreading branches. Height 24ft (7m) or more. Cultivars include 'Zebrina' with green and creamy variegated foliage.