Thunberg spiraea (Spiraea thunbergii): when and how to prune

Thunberg spiraea (Spiraea thunbergii): when to prune it?

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Straight after flowering, from late April into May. It flowers on last year’s shoots.

What else to prune in those months? April · May

Thunberg spiraea (Spiraea thunbergii): how to prune it?

1. Cut flowered shoots back to just above a strong young shoot.
2. Each year remove a third of the oldest, thickest stems at the base.
3. Leave the long young shoots: they will carry next spring’s flowers.
4. A neglected shrub can be cut right back to 20–30 cm above the ground after flowering.

How much to cut, and how often?

• One pruning period a year: April–May.
• Prune in moderation: never remove more than about a third of the shrub at once.

What does it mean for wildlife?

• Pruning in April–May can fall in the nesting season (15 March–15 August). Check carefully for nesting birds first: disturbing an active nest is against the law.
• Thunberg spiraea (Spiraea thunbergii) flowers in March–April, when it attracts bees.
• If pruning falls during flowering, wait until it is over or leave part of the plant to flower, so bees and butterflies still benefit.
• 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.
• Leaving a stub or sawing flush with the trunk: cut just outside the branch collar.

Nearby: related pruning guides

• Spiraea
• Foam of May (Spiraea × arguta)
• Japanese spiraea
• Spiraea (Spiraea × cinerea)
• Birchleaf spiraea (Spiraea betulifolia)
• Bridal wreath (Spiraea × vanhouttei)

Plant profile: Thunberg spiraea (Spiraea thunbergii) · Pruning calendar and basic rules