Shrubs like hydrangeas flower from mid to late summer on the previous year's growth. Mophead and lacecap hydrangeas will bloom satisfactorily with little attention, but regular pruning encourages new, vigorous growth that can produce a better display. Likewise, other species, including the climbing hydrangea, will benefit from a trim. Such plants fall into RHS Pruning group 4.
Timing: Usually late winter/early spring, but sometimes late summer
Difficulty: Easy to moderate
The pruning methods explained below are for individual types and species of hydrangea.
The most commonly grown hydrangeas in gardens are lacecaps and mopheads – mopheads are identified by their full, roundish heads of large petals; lacecaps have tiny flowers in the centre of the bloom and an outer border of large petals.
When to prune hydrangeas
Most pruning is carried out in late winter or early spring. However, the climbing hydrangea is pruned after flowering in summer.
How to prune hydrangeas
- Dead blooms on mophead hydrangeas can, in mild areas, be removed just after flowering, but it is best to leave them on the plant over winter to provide some frost protection for the tender growth buds below. Remove the dead flowerheads in early spring, cutting back the stem to the first strong, healthy pair of buds down from the faded bloom
Lacecaps are hardier, and the faded flowerheads can be cut back after flowering to the second pair of leaves below the head in order to prevent seed developing, which saps energy from the plant
Pruning established mopheads and lacecaps
- Cut out one or two of the oldest stems at the base to encourage the production of new, replacement growth that will be more floriferous
- Poor or neglected plants can be entirely renovated by cutting off all the stems at the base. However, this will remove all the flowers for that summer, and the new stems will not bloom until the following year
Pruning climbing hydrangeas
- The climbing hydrangea (Hydrangea anomala subsp. petiolaris) should have overlong shoots cut back immediately after flowering. Most flowers appear towards the top of the plant, so try to leave as much of this un-pruned as possible
- Established plants will tolerate hard pruning in spring, but extensive cutting back all in one go is likely to reduce flowering for the next couple of summers. To prevent flower loss, stagger drastic pruning over three or four years, reducing the size of the plant gradually
Pruning other hydrangeas
- Hydrangea serrata can be pruned in the same way as mophead and lacecap hydrangeas
- Hydrangea paniculata and Hydrangea arborescens are treated differently. Although the only essential work is to remove dead wood in spring, these species flower more prolifically when pruned back annually to a framework of branches. Each spring, cut back last year’s stems to a pair of healthy buds to maintain a permanent framework. To produce larger flower panicles on strong, upright branches, hard prune to the lowest pair of healthy buds, creating a low framework of branches. This usually results in a pruned framework of no more than 25cm (10in) high but, if more height is required, cut to about 60cm (2ft) tall
- Most other hydrangea species, including Hydrangea aspera and Hydrangea quercifolia, need only minimal pruning in spring to remove dead and over-long stems
- If there is any frost damage in spring, prune back damaged shoots to just above the first undamaged pair of buds on live, healthy wood
- Also remove any weak, straggly stems. In particular, cut out any stems that trail onto the ground
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.