Hydrangeas are stunning shrubs with gorgeous flower heads. Native to Japan, they are easy to grow and come in a huge range of colors to suit every garden style. But to maintain their growth and ensure hydrangeas bloom beautifully, you do need to prune them – and be sure you do it at the right time.
When do you prune hydrangeas? The main reason for hydrangeas not flowering properly is pruning at the wrong time. Ultimately, knowing when to prune depends on the type of hydrangeas you have planted. For example, you should prune new wood hydrangeas in late winter or early spring. If the buds have sprouted, spring will be the wrong time for hydrangeas that grow on new wood.
When to Prune Types of Hydrangeas
Before you even think of pruning hydrangeas, you need to know whether they produce flowers on new wood, which will grow in the new season, or old wood that grew during the last growing season.
But apart from differentiating between hydrangeas that bloom on old wood or new wood, the National Garden Bureau advises that the leaf and flower shape also provide important clues. So, let’s have a look at the main types of hydrangeas and when to prune them.
Hydrangea paniculata, commonly known as panicle hydrangeas, have cone-shaped flowers that start with green, cream, or white flowers. As the plant grows, the flowers turn pink. Hydrangea paniculata never has blue flowers.
Because the flowers form on the wood that grows from early spring through the growing season, they are known as new wood hydrangeas.
The time to prune is in late winter or early spring. So, you can either prune your panicle hydrangeas when they drop their leaves and go dormant or wait until the plants green up and the buds start to break.
Hydrangea macrophylla, those lovely big leaf hydrangeas, are very special when it comes to reblooming. Somehow their genetic makeup allows them to produce flowers on new stems rather than from the buds that emerge on existing stems in spring.
They are old wood hydrangeas that have pink or if planted in acid soil, blue, or even white flowers. The leaves are big, dark green, and glossy, with coarsely serrated edges.
Hydrangea macrophylla are old wood hydrangeas and they can be pruned when the flowers have faded.
Hydrangea serrata is known as the mountain hydrangea, and like hydrangea macrophylla, will rebloom even if the terminal buds are destroyed.
They are much smaller shrubs than most other hydrangeas. Its flowers, which appear on flattened flower heads, are similar to bigleaf hydrangeas. But its leaves are different, being much smaller, narrow, and pointed.
It is also an old wood type of hydrangea.
Hydrangea arborescens, also known as woodland or smooth hydrangeas, has big, round pink or white flowers. They bloom early in the growing season, and, like panicle hydrangeas, never have blue flowers.
Hydrangea arborescens are new wood flowering plants that need to be pruned in late winter or early spring before the plant starts to grow again.
Hydrangea quercifolia is more commonly called the oakleaf hydrangea because its leaves look like oak leaves. Because of this, they are valued more for their foliage than their flowers.
Oakleaf hydrangeas are old wood plants because the flower heads grow on old wood from the previous growing season. Prune in summer after the flowers have faded.
Hydrangea anomala is a climbing hydrangea that commonly relies on trees for support. Its flowers bloom on old wood and the plant doesn’t need pruning unless you need to cut it back because it’s taking over and you want to control its size.
You can cut climbing hydrangeas right back to ground level in early spring if you want to rejuvenate the plant.
How to Prune Hydrangeas
Just as you prune different types of hydrangeas at different times, the pruning process also differs.
Generally, though, new wood hydrangeas are more forgiving than those that bloom on old wood. This is because they always seem to fill in when they grow back.
Pruning New Wood Hydrangeas
There are different rules for different new wood hydrangeas.
For instance, you can prune smooth hydrangeas down to about 18 or 24 inches. Just remember that you need strong stems that will support those lovely, big flower heads, so don’t cut away too much.
As the plant grows, and the older it gets, the stronger the stems will become and you can get a bit more heavy-handed.
But when you prune your panicle hydrangeas, you can remove at least a third of the plant. If they have lost their shape (perhaps because of heavy snow) you can remove even more than this.
Pruning Old Wood Hydrangeas
Unless you are removing dead, damaged, or diseased wood (stems), don’t prune old wood hydrangeas until the buds, known as broccoli, are well established. That way you can gauge what you are removing – which should be dead or weak stems.
Also, bear in mind that some gardeners never prune their old wood hydrangeas, other than to remove dead stems.
Pruning Endless Summer Hydrangeas
Endless Summer hydrangeas are the first type bred to bloom on old wood as well as the new season’s growth of wood. It’s a stunning shrub that produces pink or blue flowers from spring through summer, depending on the pH of the soil.
The funny thing is that you don’t have to prune Endless Summer hydrangeas at all. All you have to do is to trim, removing dead stem tips only.
If your Endless Summer hydrangeas don’t bloom, chances are you have pruned them too much.
All hydrangea growers have different challenges. Here are a few tips to help you with yours.
Pruning woodland and panicle hydrangeas before they start growing in spring usually stimulates more flowers.
If the flowers of your panicle hydrangeas go brown it means they are either past their cycle or dried out. Your irrigation needs attention and you should take steps to improve water retention. A deep mulch will be helpful.
Don’t deadhead panicle flowers because this can stress the plant further. Rather, wait until the plant is dormant and all its leaves have dropped, then remove the dead flowers.
A safe rule of thumb for hydrangea varieties that bloom on old wood is to prune them before there is any sign of new growth in the spring.
Your first step in the pruning process is to first remove dead or damaged stems. When you want to shorten stems, cut back to just above healthy buds.
If your hydrangeas are damaged by winter conditions, cut them back to living wood. In other words, remove the deadwood.
We grow most types of hydrangeas for their magnificent flowers. While they are easy to grow, one sure way to stop them from flowering is to prune them at the wrong time, or the wrong way.
In this garden guide, we have given you loads of tips on when and how to prune your hydrangeas. We wish you success!