Most hydrangeas are pruned in spring, their flower heads having been left on over winter to protect the buds beneath. Climbing hydrangeas are the exception to this rule – they are pruned in summer, after flowering.
Pruning prevents hydrangeas becoming woody and congested, and channels the plants’ energy into producing strong growth and large blooms. After pruning, mulch the plant with well rotted manure or compost.
Different types of hydrangea are pruned in different ways, as some flower on old wood and some on new. Pruning incorrectly will affect flowering.
Hydrangea macrophylla, Hydrangea aspera, Hydrangea serrata and Hydrangea quercifolia are lightly pruned by cutting back the old flower heads to a pair of buds below. Hydrangea paniculata and Hydrangea aborescens can be cut back harder.
If you’re not sure which type of hydrangea you have, it’s best just to deadhead it and observe how it grows. If you notice that it produces flowers on this year’s growth, you can prune it harder next year.
Pruning hydrangeas: jump links
- Pruning mophead and lacecap hydrangeas
- Pruning Hydrangea serrata, H. aspera and H. quercifolia
- Pruning Hydrangea paniculata and Hydrangea arborescens
Mophead and lacecap hydrangeas
Mophead and lacecap hydrangeas (Hydrangea macrophylla) flower on the previous years’ growth. They are an exception to the rule that says shrubs that produce their flowers on the previous season’s growth should be pruned after flowering. The structure of hydrangea stems means that it’s best to leave cutting back until spring. This is because the stems are cork-like, rather than woody, and hold enough moisture inside them during winter for this to freeze in frosty weather. If they are pruned in autumn, after flowering, the buds can freeze, killing the stems and their buds. Leaving the old flowers on the plant over winter, until the worst frosts are over, will help protect the stems and their new buds. Once the sap starts to rise in spring, these buds will open and many should go on to carry blooms the following year.
Remove last year’s flowerheads
In April, remove old flowerheads to just above a pair of buds. Hydrangea buds can be easily knocked off, so cut carefully using the tips of your secateurs. If the plant has many stems, cut at an angle between the buds to remove one of the pair. This will direct growth into one shoot rather than two, preventing the plant from becoming congested.
Cut out thin, weak stems
Cut out any thin, weak stems around the base of the plant and remove one or two of the largest, oldest stems from as low down as possible to promote new shoots from the base. These will grow over the next few years and carry blooms in the future.
If you have an overgrown plant, cut some of the stems right to the base.
Hydrangea aspera and Hydrangea serrata
Hydrangea aspera, Hydrangea serrata and Hydrangea quercifolia are also lightly pruned in spring – just remove old flower heads and old, crossing or long stems and in a similar way to mopheads and lacecaps.
Hydrangea paniculata and Hydrangea aborescens
Hydrangea paniculata and Hydrangea aborescens produce flowers on new wood, which means that you can cut them back harder without losing this year’s flowers. Pruning is not essential, but left unpruned the plant will get taller, with most of the flowers at the top.
Cut back to a healthy framework
Cut back in early spring, pruning last year’s growth back to a healthy framework that’s between 30cm and 60cm high. Prune to just above a pair of healthy buds on each stem. Cut back to the lowest healthy buds for big flowers or less hard for a natural look or a taller plant.
Watch Monty Don explain the different ways of pruning hydrangeas in spring:
Pruning climbing hydrangeas
Climbing hydrangeas such as Hydrangea anomola subsp. petiolaris and Hydrangea seemannii should not be pruned until after they have flowered, in summer.