Photo: Keckler, CC BY 3.0 · source
Pruning guide · Shrub
Smooth hydrangea (Annabelle): when and how to prune
Hydrangea arborescens
Prune a smooth hydrangea in March, before the new shoots appear: cut all stems back to 20–30 cm above the ground, just above a pair of buds, or to 40–50 cm for sturdier stems.
The smooth hydrangea, best known as the variety ‘Annabelle’, flowers from June into September with huge white balls. It flowers on new wood: the flowers come on this year’s shoots. So you can cut it back hard every spring without losing flowers, and it flowers even after a severe winter. The height you prune to decides how sturdy the stems become: prune a little higher and the heavy flowers flop less after a downpour.
| Pruning months | March |
|---|---|
| Nesting season (15 March–15 August) | Take care in March |
| Flowering | June–September |
| Good for bees, butterflies and birds | Yes, for bees |
| Native to Belgium | No, planted |
Smooth hydrangea (Annabelle): when to prune it?
Prune in March, before the new shoots appear.
Leave the faded flower heads all winter: they look lovely with frost, and insects overwinter in them.
Don’t prune in summer: you would cut off that year’s flowers.
What else to prune in those months? March
Smooth hydrangea (Annabelle): how to prune it?
- Cut all stems back to 20–30 cm above the ground, just above a pair of buds.
- If you leave them 40–50 cm long, you get a sturdy framework and the flowers flop less.
- Remove thin, weak and dead stems completely at the base.
- Every few years, take out a few of the oldest stems at ground level, so the shrub stays young.
- If the flowers still flop, put a plant support or a ring around the shrub in April.
How much to cut, and how often?
- Every year all the stems, to 20–30 cm or 40–50 cm.
- Every few years, also a few old stems at ground level.
What does it mean for wildlife?
- March falls mostly before the nesting season (from 15 March). Hardly anything nests in a low, bare hydrangea in March, but do take a look.
- The rounded heads of ‘Annabelle’ consist almost entirely of sterile flowers, with little for insects. For wildlife, choose a variety with flat heads full of small fertile flowers, or combine it with native flowering plants.
- The dry flower heads shelter ladybirds, spiders and other small insects in winter. Only cut them off in March.
- Put the prunings on the compost heap or leave them in small pieces under the shrub: they feed the soil life.
Common mistakes
- Pruning it in summer, so the flowering is lost.
- Never pruning, so the shrub is full of thin stems and the flowers stay small.
- Leaving all the thin stems, so the flowers flop at the first downpour.
- Cutting off the dry flower heads in autumn.
Caution: It flowers on new wood: hard pruning in spring costs no flowers, pruning in summer does.
Nearby: related pruning guides
Plant profile: Smooth hydrangea (Annabelle) · Pruning calendar and basic rules