Thuja plicata

RHS Plant Profile

western red cedar

RHS

Other common names

British Columbia cedar, Californian white cedar, giant arbor-vitae, Nootka Sound arbor-vitae, western arbor-vitae, yellow cypress

Synonyms

Thuja gigantea
Thuja lobbii

Conifers Trees

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A large, evergreen, narrowly-pyramidal tree reaching an ultimate height of up to 35m. Aromatic, glossy, scale-like, sharply-pointed mid to dark green leaves are held in large drooping sprays on spreading branches that curve upwards at the end. Cones are egg-shaped and around 1.3cm long

Position

Full sun, Partial shade

Soil Types

Chalk, Clay, Loam, Sand

Max Height

Higher than 12 metres

Max Spread

wider than 8 metres

Size

Time to Maturity: 10–20 years
Max Spread: wider than 8 metres
Max Height: Higher than 12 metres

Growing Conditions

Chalk Clay Loam Sand

Moisture: Moist but well–drained or Well–drained
pH: Acid or Alkaline or Neutral

Position

Full sun Partial shade

Aspect: North–facing or West–facing or South–facing or East–facing
Exposure: Exposed or Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

H1A: under glass all year (>15C)
H1B: can be grown outside in the summer (10 - 15)
H1C: can be grown outside in the summer (5 - 10)
H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
H4: hardy through most of the UK (-10 to -5)
H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
H6: hardy in all of UK and northern Europe (-20 to -15)
H7: hardy in the severest European continental climates (< -20): H6

Colour & Scent

Fragrance Foliage

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Cupressaceae
Native to GB/Ireland: No
Foliage: Evergreen
Habit: Columnar upright
Potentially harmful: Harmful if eatenskin allergen. Wear gloves and other protective equipment when handling
Genus: Thuja are fast-growing evergreen trees of narrowly conical habit, with flat sprays of tiny, aromatic, scale-like leaves and small knobbly cones
Name Status: Correct
Plant Range: W North America

How to Grow

Cultivation

Grow in moist but well-drained soil in full sun with shelter from cold, drying winds. See conifer cultivation for further advice

Propagation

Propagate by semi-ripe cuttings in late summer; propagate by seed in late winter in containers in a cold frame

Suggested planting locations and garden types

Architectural
Low Maintenance
Hedging and screens

Pruning

No pruning required; trim in spring and late summer if grown as a hedge

Pests

May be susceptible to scale insects and conifer aphid

Diseases

May be susceptible to diseases including honey fungus, Phytophthora root rot and thuja blight. See conifers: brown patches for further advice