Spiraea: when and how to prune

Spiraea: when to prune it?

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Cut a summer-flowering type, such as Japanese spiraea, back in March, before it comes into leaf. It flowers on the shoots that grow afterwards, so you lose no flowers.

Prune a spring-flowering type, such as bridal wreath, straight after flowering, in May or early June. It then makes the shoots that will flower the following spring.

If in doubt, wait until it has flowered: small white clusters along the stems in spring mean prune after flowering; pink heads at the tips in summer mean prune in March.

What else to prune in those months? March · May · June

Spiraea: how to prune it?

1. In March, cut a summer-flowering type back with secateurs to 20–30 cm above the ground, just above a few buds. It quickly regrows and stays compact.
2. A low hedge or edging of Japanese spiraea can simply be trimmed with a hedge trimmer in March.
3. On an older summer-flowering type, also take a few of the oldest, thickest stems out at the base every few years, so young ones can replace them.
4. Thin a spring-flowering type after flowering: saw a few of the oldest stems off at the base, roughly one in five on a mature shrub.
5. Cut the flowered stems of a spring-flowering type back to a strong young shoot growing outwards. Don’t clip it all over: its graceful, arching shape would disappear.
6. On Japanese spiraea, cut off the faded flower heads in summer: it will often flower a second time. Leave the last heads on until the March prune.

How much to cut, and how often?

• Cut a summer-flowering type back firmly every March; thin a spring-flowering type a little every year after flowering. One prune a year is enough.
• On a spring-flowering type, remove no more than a fifth to a quarter of the stems at once, unless you are deliberately rejuvenating an old shrub.
• Cut an old, bare shrub back hard: a summer-flowering type in March, bridal wreath after flowering. It will regrow, although bridal wreath then flowers less for a year.

What does it mean for wildlife?

• The flowers of both groups attract honeybees, solitary bees and hoverflies, and in summer butterflies also feed on the flat pink heads of Japanese spiraea.
• Pruning spring-flowering types in May–June falls in the nesting season (15 March–15 August): blackbirds or dunnocks sometimes nest in a large, dense bridal wreath. Look carefully first, as disturbing an active nest is against the law.
• Pruning summer-flowering types in March usually comes before the birds start nesting. Leave the faded heads on until then: small insects and spiders overwinter among them, and they give the garden some structure in winter.
• Ladybirds and hoverfly larvae usually clear the aphids on the young tips by themselves. Prunings can go on a dead hedge, shelter for hedgehogs and insects.

Common mistakes

• Cutting bridal wreath back in winter or early spring, so it doesn’t flower that year.
• Clipping a spring-flowering type into a ball every year, so its graceful, arching stems disappear.
• Never cutting back Japanese spiraea, so it flops, turns woody and goes bare at the base.
• Pruning a spring-flowering type after flowering without checking for nests first.

Nearby: related pruning guides

• Japanese spiraea
• Foam of May (Spiraea × arguta)
• Ninebark
• Weigela
• Forsythia

Similar to: Difference from cotoneaster

Plant profile: Spiraea · Pruning calendar and basic rules