Knowing how to prune hydrangeas is a very important part of keeping these beautiful plants. Hydrangeas are often foundational shrubs found in the garden. Their blooms are large, striking in color, and they can form an attractive feature in front of a home, a walkway, or any other landscape. To get the best flowers out of your hydrangea, you need to prune it. But this means you also need to know how to prune it successfully.
Many people are anxious about pruning plants and not sure of the best way to go about it. If you’re new to plants, hydrangeas are a good one to start with. They make great focal points in the garden and they don’t need a lot of care, apart from some minimal pruning and fertilizing. Today, we’re going to focus on the pruning aspect of caring for hydrangeas.
Although there is some contention about when to prune old wood hydrangeas, the best time is at the end of summer. New wood hydrangeas should be pruned at the beginning of spring.
Hydrangeas do not need much pruning, but you can shape and prune them to influence flower growth. And of course, you should also prune to remove dead branches or decaying blooms or flower buds that didn’t quite take off. You will often see more of this in late winter, as your plant is transitioning through the seasons, and this is when it’s a good idea to do a little trimming.
Hydrangeas come in different species, and it is essential to know which species you are dealing with. Pruning times differ for the various species.
Tips on How to Prune Hydrangeas
Let’s first take a quick look at some tips for pruning this species:
- prune in the summer or late winter/early spring (depending on the variety – more on this later)
- cut away dead, brown, or weak stems
- prune flowers from just above the new buds
- prune frost-damaged stems to the first pair of buds
- shape the entire plant while pruning – stand back to get a better look, if needed
When removing dead parts, you can’t really prune at the wrong time, however, there are some ideal times for certain types of pruning and shaping. Let’s explore this more.
When To Prune Old Wood Blooming Hydrangeas
Mophead hydrangeas are the most commonly known type of hydrangea with their big purple-blue or pink flower heads. Lacecap hydrangeas have a round central disc of shorter flowers with a frill of showy flowers.
These two types of hydrangeas are known as Bigleaf hydrangeas, and they bloom on old wood or last season’s wood. This is important as it affects pruning techniques.
Some gardeners advise pruning just after the plants have finished flowering at the end of summer, but others argue that the end of summer is not ideal. What has happened in a previous season and how you prune and prep can affect the next season.
Some say leaving the dead flower heads on the plant through winter protects the underlying branches and developing buds from late frosts or cold snaps. Gardeners subscribing to this view say it is best to prune bigleaf hydrangeas at the end of winter.
Gardeners subscribing to the end-of-summer pruning schedule feel that pruning old wood blooming hydrangeas at the end of winter creates the risk of cutting off the new buds.
This argument makes considerable sense when considering that these hydrangeas begin setting buds for the coming season towards the end of fall. Unless you are confident about not cutting new buds, it is probably best to prune these hydrangeas after blooming. I will leave this to your judgment and you can decide based on your own comfort level.
Oakleaf hydrangeas, climbing hydrangeas, and mountain hydrangeas also bloom on old wood. They should also be pruned at the end of summer or when the blooms have died off.
How To Prune Hydrangeas That Bloom On Old Wood
When dealing with hydrangeas that bloom on old wood, it is essential not to cut off stems that will produce the next season’s flowers. Here are the hydrangeas that bloom on old wood:
- Bigleaf hydrangea (H. macrophylla cvs., USDA Hardiness Zones 6–9)
- Climbing hydrangea (H. petiolaris), Z 5-7)
- Oakleaf hydrangea (H. quercifolia, Z 5–9)
- Mountain hydrangea (H. serrata, Z 6-9)
Some people believe that these hydrangeas do not need pruning. The problem is the dead flower heads impair the growth of the new buds, and the plant becomes congested with dead plant material. This makes it look untidy and masks the current season’s blossoms.
Harsh pruning of these hydrangeas should be avoided. Just cut off dead, diseased, or broken branches. Remove the flower heads as they die to keep the bush looking tidy. If you choose to cut off old wood, look for thin, weedy stems or ones several seasons old and cut them off at the base. This will encourage new stems or canes to form in the spring.
You can prune the bush more harshly if you need to trim it back for size purposes. Remember, though, that those severely trimmed branches will have no blooms in the next season.
Do not prune more than 30% of the hydrangea bush as it will suffer from stress, resulting in it not flowering and struggling for the next few seasons. In severe conditions, it may die if you cut it back too much.
Bigleaf hydrangeas are vulnerable to the cold, and severe pruning combined with cold may be too much for the plant.
When To Prune New Wood Hydrangeas
Not all hydrangeas bloom on old wood. Some, like the ones below, will bloom on new wood:
- Panicle hydrangea (H. paniculata and cvs., Z 4–8)
- Smooth Annabelle hydrangea (H. arborescens and cvs., Z 4–9)
These plants blooom later because they need to grow and set buds in the same year that they bloom. They can begin in midsummer and then continue until the first frost, depending on your specific climate and the conditions they are being grown in. They can also be more forgiving if you do not prune at a specific time. The key is just to not prune when the flower buds are first opening.
So, when should you prune hydrangeas that bloom on new wood?
For hydrangeas that bloom on the current year’s growth, it is usually advised to cut them back in the late winter or early spring, before any new growth begins.
How To Prune Hydrangeas That Bloom On New Wood
Cut each branch back by approximately one-third to encourage new stems to form. Choose a place on the cane just above a node when making the cut.
Cut away any weak, broken, diseased, or thin branches. These hydrangeas benefit from relatively severe pruning, but it is important to know how much your prune can affect the flowers.
A harsh pruning on smooth hydrangeas involves cutting the branches to fifteen or sixteen inches above the ground. This approach will result in fewer flowers, but they will be larger. The shorter stems will hold up the flowers better than if these large blossoms grow on a longer cane.
A light pruning of smooth hydrangeas will result in more flower heads, but they will be smaller. A similar result can be obtained with panicle hydrangeas. However, it is important to trim out any thin stems if you aim to grow big flower heads. The thicker stem framework will support the blooms better.
Learn More About Pruning
FAQ About Pruning hydrangeas
My hydrangea is getting too tall: how do I prune it?
Hydrangeas growing too tall can be corrected by removing the tallest canes or stems at the soil line. This will encourage new canes to shoot while allowing the old wood’s shorter stems to bloom in the current season.
Remember that you can also use a framework to help you shape your hydrangea as it grows.
My hydrangeas look weak and weedy: what should I do?
Hydrangeas that are weedy and weak need to be helped by pruning off the thin, weak, or diseased stems. Cutting these down at the soil line will encourage new canes and give added vigor to your plant.
What tools should I use to prune hydrangeas?
The best tool to prune your hydrangea is a bypass secateurs or pruner. These act in a similar way to scissors and provide a clean cut without crushing the canes. With time and practice, you may find you like a particular brand or size better, but in general, these are the best tools. Also make sure they are clean, sharp, and in good condition before using them on your plants.
It is critical to keep pruning tools sharp to avoid damaging the plant. Clean and disinfect the pruning tools after use to prevent diseases from passing from one plant to another.
It’s easy to see that there are several steps to pruning and maintaining your hydrangeas to keep them in the best possible condition. Hydrangeas do not need heavy pruning, but they need deadheading and light pruning to prevent the plant from becoming congested. Pruning to influence shape and flower production can be done for the overall appeal of the plant.
Weak hydrangeas that are not thriving can be helped by removing dead and weak canes to stimulate new growth. Use sharp bypass pruners when pruning hydrangeas.
Do you have any tips that you would add to our post on this topic? We’d love to hear it in the comments.
Adriana Copaceanu is a passionate nature lover living in the country on her dream property where she grows vegetables, lavender, and wildflowers that she shares with the wildlife they attract. When she's not in the garden, she loves spending time with her chickens and planning her next nature project. Check your her books below: