Hydrangea pruning has to be one of the most satisfying jobs in the garden. It’s easy, there are no prickles, no ladders, and the shrubs look smart and tidy instantly.
Hydrangeas can be divided into three groups for pruning. The first group is Hydrangea macrophylla, the common hydrangea (the “ordinary” one) with either mophead or lacecap flowers, and Hydrangea serrata. These hydrangeas flower on old wood, that is stems that grew the previous year, or years. The first thing to do is to have a good look at the plant, identify and remove any dead, diseased or damaged wood. The remaining stems are reduced by about 30cms, cutting above a pair of fat buds. These buds will develop into flowers in the coming season. On mature hydrangeas it is a good idea to remove some of the oldest stems to make room for new growth. Cut them off right at the bottom. You will often see new shoots already forming. This keeps the plant vigorous and healthy. If this is not done, the plant can become congested which makes it difficult to manage, and will result in a mass of smaller cramped flower heads. Old, neglected hydrangeas can become very tall and untidy, but all is not lost; cutting the whole plant right down to the base and starting again is the best option, though you will get no flowers in the coming year. It is good practice to apply some general purpose fertiliser as you prune. We use a handful of chicken manure pellets for each bush.
H macrophylla is pruned in late spring, traditionally in Lent. Leaving the old growth and dead flower heads on the plant until then provides the new buds with some protection from frost. However many gardeners prefer to get it done earlier, before the garden gets really busy. It is a risk, but not a big one in mild parts of the country, and though frost could cause damage it is unlikely to be serious and the hydrangea will grow out of it. Those of you who are familiar with Trebah will know there are two acres of hydrangeas in the valley. The late Mrs Hibbert who lived there for many years pruned these herself in Lent. It took her all of 40 days and she described it as her Lenten penance.
The second group of hydrangeas include Hydrangea arborescens (such as Annabelle) and Hydrangea paniculata (such as Limelight). These flower on wood that grows in the current year. They are pruned by cutting the whole plant back to the lowest pair of healthy buds. This will mean removing all the stems almost to ground level and creating a short stubby framework. This can be done in early spring before growth commences. If the plant is not pruned, or is not cut all the way back, there will be more blooms which will be smaller and higher up. For plants like
H ‘Annabelle’ this may be considered preferable to having the huge melon sized flower heads which have a tendency to flop unless staked.
The third group includes Hydrangea aspera, H aspera Villosa Group, H quercifolia and H sargentiana.
These do not require regular pruning. Minimal pruning to remove dead, damaged or unruly stems can be done in spring.
Remember that hydrangeas do not have to be pruned, and nothing terrible will happen if they aren’t. It’s a way of controlling the way the plant flowers and getting the best performance to fit in with our gardening standards.