How To Prune Hydrangeas.

Despite what you may read, most Hydrangeas do require annual pruning. And the reasons are simple. If you want to keep your Hydrangeas in good shape, producing lots of large flowers and prolong their productive life, you need to prune them. Some need a lot of pruning, some very little, however all will benefit.

And they are easy to prune, if you know what sort of wood your hydrangea flowers on you will know when to prune it.

Hydrangeas come in a range of types or species, and different Hydrangeas require different pruning techniques, they need to be pruned at different times. The main thing to consider with hydrangeas is to find if it is a type that flowers on old wood, or new wood.

Once we know how they flower, we know the best time to prune hydrangeas.

For example, those that flower on old growth are best pruned just after after flowering. This allows them to put on some new growth before winter. So as the flowers begin to look a little sad prune away.

As you can see from the image right, Hydrangeas can put out strong growth in the year after pruning. The same plant is pictured below, showing 1m (3ft) of growth in a season.

When to Prune Hydrangeas

And when do we prune those that flower on new growth, in spring in the colder climate as this gives then some protection from the rigours of winter. Although in warmer areas in autumn is OK.

What happens if you prune your hydrangeas at the wrong time ? The worst that can happen is they will not flower or have few flowers.

Hydrangeas are generally pruned in late summer or winter to early spring. And again, It needs to be remembered that some Hydrangeas flower on the previous years growth so heavy pruning can inhibit flowering.

Hydrangea showing new growth after pruning

Hydrangea pruning basics

Pruning basics say that we should remove any dead or diseased (damaged) growth, this is true with all plants and Hydrangeas are no exception.

You also need to determine if you are pruning for shape, or to encourage flowering, especially with hydrangeas as some flower on new wood other on old wood.

Pictured right we show the new growth in one season, if left unpruned Hydrageas can become very lanky and unattractive over 2 years.

Pruning the different Hydrangea Varieties

Pruning Mophead Hydrangeas, Lacecaps and Hydrangea Serrata
These plants flower on last seasons wood.
Prune back growth down to the first pair of healthy buds on each stem.
But start by removing any dead or diseased growth, these growths can be pruned right back.
Consider cutting 25% of the oldest growth out each year, this will encourage new growth from the base of the plant. In frost prone areas consider leaving pruning until frosts are over, the old growth and flower heads will provide protection from frosts.
Old plants can be pruned back heavily to reinvigorate the plant, but remember you will have no flowers that year.
Pruning Hydrangea paniculata and Hydrangea arborescens.
These two flower on current seasons growth or new wood.
Old and diseased wood needs to be removed.
In early spring they can pruned back to the lowest pair of healthy buds flowering will be be more prolific.
Pruning Hydrangea aspera, Hydrangea quercifolia (Oak Leaf Hydrangea), Hydrangea sargentiana and Hydrangea villosa.
These also bloom on old wood and do not require heavy pruning unless they get out of shape.
Remove dead, and diseased wood.
Prune thin or weak stems and cut back to the first pair of healthy buds.
Pruning Climbing Hydrangeas.
Climbing Hydrangeas are best pruned just after flowering in summer.

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John Allman

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