Western red cedar (Thuja plicata)

Photo: Jean-Pol GRANDMONT, CC BY-SA 3.0 · source

Pruning guide · Conifer

Western red cedar: when and how to prune

Thuja plicata

Western red cedar: as a hedge or grown freely, prune in May–June and August–September.

Key facts
Pruning monthsMay–June and August–September
Nesting season (15 March–15 August)Take care in May–June and August
Native to BelgiumNo, planted
Poisonous to people and petsYes, take care with children and pets

Western red cedar: when to prune it?

Trim a hedge in May–June and late August, by mid-September at the latest. Check first that no birds are nesting.

What else to prune in those months? May · June · August · September

Western red cedar: how to prune it?

  1. Only cut into the green. It tolerates pruning better than most conifers, but a bare, brown patch fills in slowly, if at all.
  2. Keep the hedge slightly narrower at the top than at the bottom, and cut back the top as soon as it reaches the height you want.
  3. A free-standing tree needs no pruning; leave the lower branches.

How much to cut, and how often?

  • Trim a hedge once or twice a year, after the first flush of growth (late June) and, if needed, in late summer. Check first that no birds are nesting.
  • Most conifers do not regrow from old, bare wood. So never cut back into the brown part (exception: yew).

What does it mean for wildlife?

  • Pruning in May–June and August can fall in the nesting season (15 March–15 August). Check carefully for nesting birds first: disturbing an active nest is against the law.
  • A dense hedge gives birds a place to nest and shelter, and hedgehogs take cover underneath. Leave some leaves at the base.
  • Prunings can go on a dead hedge or brash pile in a corner of the garden: shelter for hedgehogs, wrens and insects.

Common mistakes

  • Clipping without first checking for nesting birds.
  • Cutting back into bare brown wood: it will not regrow from there.
  • Letting the hedge grow wider at the top than at the bottom: the base then goes bare.

Caution: Check first that no birds are nesting, and wear gloves: the sap can irritate the skin. Western red cedar is poisonous: wear gloves and keep clippings away from children, pets and livestock.

Nearby: related pruning guides

Similar to: Difference from Lawson cypress · Difference from northern white cedar

Plant profile: Western red cedar · Pruning calendar and basic rules

This guide is compiled from the Bladwijzer plant profile and pruning calendar.

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