UK pruning guide · RHS timing
When to prune western red cedar in the UK
Why the timing differs here
RHS guidance puts evergreen pruning in mid to late spring, once the risk of a hard frost has passed. Cutting evergreens in a British winter exposes soft new growth to frost damage, which is why the timing sits later here than in milder climates.
How to prune western red cedar
For hedges, shear the outer surface keeping a slight taper (wider at base) so lower branches receive light. For specimen trees, thin by removing entire side branches to the collar rather than shearing. Always retain green foliage on retained wood.
Western Red Cedar (Thuja plicata) responds well to pruning and tolerates shearing better than most conifers. Prune to shape hedges or reduce size in late winter to early spring before new growth, or again lightly in late summer. Remove dead inner foliage and crossing branches. Avoid cutting back beyond green foliage — bare brown wood rarely regenerates.
More western red cedar care for British gardens
Care at a glance
Pruning western red cedar in the UK — FAQ
When should I prune western red cedar in the UK?
Prune western red cedar in mid to late spring. RHS guidance puts evergreen pruning in mid to late spring, once the risk of a hard frost has passed. Cutting evergreens in a British winter exposes soft new growth to frost damage, which is why the timing sits later here than in milder climates.
Is it illegal to prune western red cedar in spring or summer in the UK?
Pruning itself is not illegal, but destroying an active nest is. Under the Wildlife and Countryside Act 1981 it is a criminal offence to damage or destroy the nest of any wild bird while it is being built or in use, and the RHS treats the nesting season as March to August, sometimes longer. Check western red cedar for nests before cutting, and if you find an active one, leave that part of the plant until the birds have fledged.
How do you prune western red cedar?
For hedges, shear the outer surface keeping a slight taper (wider at base) so lower branches receive light. For specimen trees, thin by removing entire side branches to the collar rather than shearing. Always retain green foliage on retained wood.
How often does western red cedar need pruning in a British garden?
Annually for hedges; every 2–3 years for specimen shaping. Western Red Cedar (Thuja plicata) responds well to pruning and tolerates shearing better than most conifers. Prune to shape hedges or reduce size in late winter to early spring before new growth, or again lightly in late summer. Remove dead inner foliage and crossing branches. Avoid cutting back beyond green foliage — bare brown wood rarely regenerates.
Why is UK pruning timing different from American advice?
Most pruning guides online are written for US conditions and anchored to USDA zones. Britain's maritime climate gives milder winters but later, less predictable last frosts — from March in the south-west to mid-May in the north — so the RHS advises against winter pruning for most plants: it pushes out soft growth that a late frost then kills. Britain also has the nesting-bird law, which has no US equivalent.