Forsythia: when and how to prune

Forsythia: when to prune it?

JFMAMJJASOND

Prune straight after flowering, in April or early May, when the last flowers have faded and the first leaves appear.

By the end of May the job should be done: in summer the shrub forms next year’s flower buds, and whatever you cut off then won’t flower.

Don’t prune in autumn or winter, and don’t clip it into a ball: the flower buds disappear and it barely flowers in spring.

What else to prune in those months? April · May

Forsythia: how to prune it?

1. Look at the shrub first: the oldest stems are thick, dark and much branched, and mostly flower only at the top. Young stems are paler, straight and carry most of the flowers.
2. Every year, saw a few of the oldest stems off close to the ground, roughly one in five on a mature shrub. Don’t cut them halfway down: a broom of thin shoots then sprouts just below the cut.
3. Cut back flowered stems that are too long or arch too far to a strong young side shoot facing outwards: the shrub then keeps its loose, arching shape.
4. Remove dead, weak and crossing stems, as well as stems that touch the ground and root, unless you want a new shrub from them.
5. Rejuvenate a neglected, bare shrub over three years: each year a third of the oldest stems out at the base. Or cut it back to 30 cm in one go after flowering: it will regrow, but flower little the following year.
6. After pruning, spread some compost or a layer of leaves around the base: the shrub will then put out strong new shoots.

How much to cut, and how often?

• One prune a year, straight after flowering, is enough. Just let a young shrub grow for the first two or three years.
• Take a few of the oldest stems out at the base every year: the shrub then renews itself completely every four to five years without ever going bare.
• To keep it smaller, take out more old stems at the base rather than trimming the tips: trimmed tips produce a dense mass of thin twigs that flowers poorly.

What does it mean for wildlife?

• Blackbirds, song thrushes and dunnocks like to nest in a dense, older forsythia, sometimes as early as April. Pruning after flowering therefore falls in the nesting season (15 March–15 August): check between the stems first, as disturbing an active nest is against the law.
• For all its bright yellow, forsythia has little to offer bees: its flowers produce hardly any nectar or pollen. Plant a cornelian cherry, a goat willow or a blackthorn alongside it: they flower just as early and are full of bees and bumblebees.
• Bullfinches sometimes eat the flower buds in winter. That is a shame for the display, but there are usually plenty left: let them have their meal.
• Prunings can go on a dead hedge in a corner of the garden: shelter for hedgehogs, wrens and insects. Young twigs also root easily as cuttings.

Common mistakes

• Pruning in autumn or winter, so the flower buds are gone and the shrub barely flowers in spring.
• Clipping the shrub into a ball or block every year, so it only flowers a little on the surface.
• Only trimming the tips and never removing old stems at the base, so the shrub goes bare at the bottom.
• Pruning too late, in summer, when the new flower buds are already forming.

Nearby: related pruning guides

• White forsythia
• Lilac
• Cornelian cherry
• Weigela
• Spiraea

Similar to: Difference from cornelian cherry · Difference from Japanese kerria · Difference from winter hazel · Difference from winter jasmine

Plant profile: Forsythia · Pruning calendar and basic rules