Courses
Free lessonPruning made simple · lesson 2 of 10

When to prune: the flowering rule

The one question that decides when to prune almost any shrub, the RHS pruning groups, and the times to avoid.

Key points

The flowering ruleFlowers on last year's stems (spring, early summer): prune straight after flowering. Flowers on this year's stems (late summer, autumn): prune in early spring.
RHS pruning groupsNumbered groups on RHS plant pages: 1 light, 2 after flowering, 6 early spring, 7 hard for stems, 8 mostly left, 10 light trim.
Unsure?Remove the three Ds only, and watch when it flowers.
AvoidHard frost; birches and maples from late winter into spring; plums and cherries in winter; hedges with active nests.

Summary

Flowers inFlowers onPrune
Spring, early summerLast year's stemsStraight after flowering
Late summer, autumnThis year's stemsEarly to mid-spring
Grown for stems(not for flowers)Hard, late winter or early spring
EvergreensVariesLightly; after flowering or mid-spring

Quick check

A shrub flowers in May. When should you prune it?
  1. In early spring, before it flowers
  2. Straight after it finishes flowering
  3. In autumn, when the leaves fall
  4. In midwinter, while it's dormant
Answer: B. May flowers grow on last year's stems. Pruning after flowering gives it all summer to grow next year's.
Buddleja flowers in late summer on stems grown that year. When is it pruned?
  1. Straight after flowering
  2. In midsummer
  3. In late autumn
  4. In early to mid-spring
Answer: D. A spring cut leaves the whole season for new flowering stems to grow.
What does a plant in RHS pruning group 1 need?
  1. Only the three Ds: dead, diseased, damaged
  2. A hard cut to the ground each spring
  3. Cutting back straight after flowering
  4. Two trims a year, summer and winter
Answer: A. Group 1 is evergreens and most trees, which are best left to grow naturally.

In your garden

  • List the shrubs you have.
  • Write down when each one flowers.
  • Mark each 'after flowering' or 'early spring'.

Video transcript

Most pruning mistakes are about timing, not technique. This lesson gives you the one rule that decides when to prune almost any shrub, and how the RHS pruning groups use it.

Ask one question: does it flower on last year's stems, or on this year's? Shrubs that flower in spring and early summer, like forsythia, bloom on stems grown last year, so prune them straight after flowering. Shrubs that flower from late summer, like buddleja, bloom on stems grown this year, so prune them in early spring. Prune at the wrong time, and you cut off this year's flowers.

The RHS sorts woody plants into numbered pruning groups, shown on its plant pages. Group one needs very little: just the three Ds. Group two is pruned after flowering, like forsythia and weigela. Group six is cut back in early spring, like buddleja. Group seven is cut hard in late winter for coloured stems, like dogwood. Group eight, such as camellias, is mostly left alone. And group ten, like lavender, gets a light trim.

For any plant, first note when it flowers. Then look up its pruning group on its RHS plant page. If there's no label, look at the stems: flowers on long, new shoots mean this year's growth. And if you're still unsure, just remove the three Ds for now, and watch when it flowers next year.

A few times to avoid. Don't prune in hard frost, as cut stems can die back. Birches and maples bleed sap if cut from late winter into spring, so prune them from late summer to midwinter. Plums and cherries can catch silver leaf disease through winter cuts, so prune them in spring or summer. And never cut a hedge with an active bird's nest in it.

This is one of 10 lessons in Pruning made simple

The full course adds sorting drills, flashcards and a printable summary sheet for every lesson.

See the course