Hydrangeas are low-maintenance shrubs that delight us with their beautiful lush flowers from summer to late fall (depending on the variety). But should you prune your hydrangea? And if so, when and how much? This article will tell you everything you need to know about pruning hydrangeas.
Table of Contents
- Which hydrangea do you have?
- Pruning hydrangea: when and how much?
Which hydrangea do you have?
Pruning hydrangeas helps the shrub keep its beautiful shape and be in full bloom year after year. The method and timing of pruning depends on the type of hydrangea, so it’s important to know which type you have. If you prune your hydrangeas at a time of year that is not suitable for them, you may cut off the flower buds that will bloom the following season.
When it comes to pruning, hydrangeas fall into two distinct groups: Hydrangeas that bloom on annual wood and hydrangeas that bloom on perennial wood that is at least two years old.
Hydrangeas in pruning group 1 – light pruning after blooming in the fall.
Determine if your hydrangea is blooming on old wood. In other words, whether its flowers bloom from buds created the previous year. Hydrangeas with this characteristic usually bloom in early summer and die back in mid-summer. At this time, the plant begins to form flower buds that will produce flowers the following year.
Hydrangeas that form their flower buds on biennial wood include these species:
- Peasant hydrangea (Hydrangea macrophylla)- ‘Dragonfly’, ‘Deep purple’, ‘Zorro’, ‘Caipirinha’, ‘Everbloom’, ‘Kanmara’, ‘Cardinal’, ‘Avantgarde’.
- Oakleaf hydrangea (Hydrangea quercifolia)
- Plate hydrangea (Hydrangea serrata) – ‘Preziosa’, ‘Koreana’
- Velvet hydrangea (Hydrangea aspera) – ‘Hot Chocolate
- Climbing hydrangea (Hydrangea petiolaris)
Hydrangeas of pruning group 2 – pruning before budding, in spring.
These hydrangeas produce new shoots each spring, on which flowers appear later in the summer. They bloom later than hydrangeas of pruning group 1, because they need more time for the formation of flower buds.
The following hydrangea species form their flower buds on one-year-old wood:
- Snowball hydrangea (Hydrangea arborescens) ‘Annabelle’ & Hydrangea ‘Strong Annabelle’, ‘Snowball’.
- Panicle Hydrangea (Hydrangea paniculata) – ‘Kyushu’, ‘Limelight’, ‘Levana’, ‘Pink Lady’, ‘Baby Lace’, ‘Pinky Winky’, ‘Phantom’, ‘Skyfall’ ®, ‘Switch® Ophelia’, ‘Unique’, ‘Vanille Fraise’, ‘Confetti’, ‘Candlelight’, ‘Magical Candle’ ®.
- Hydrangea Forever & Ever ® (the only Hydrangea macrophylla that blooms on new wood).
- Hydrangea Endless Summer ® – ‘Summer Love’
Pruning hydrangea: when and how much?
It is not obligatory to prune a hydrangea of pruning group 1. So it’s not so bad if you don’t do it for a few years. The best time to prune a pruning group 2 hydrangea is early spring, around mid-March or April. Only the climbing hydrangea should be pruned back after blooming in the summer. Choose frost-free weather to allow pruning wounds to heal properly. It’s also a good idea to leave the wilted flowers on the plant throughout the winter, as they provide extra protection from night frost. Still make sure that you always use sharp pruning shears. This will give you clean cuts from which the plant will recover more quickly.
Pruning group 1: Hydrangeas that bloom on old wood.
Hydrangeas that bloom on old wood, such as the farmer’s hydrangea (h. macrophylla), oakleaf hydrangea (h. quercifolia) and climbing hydrangea (h. petiolaris) don’t really need pruning at all. These hydrangeas should only be pruned if the plant has grown too tall or too wide. You only need to remove the dried flowers by cutting them off below the panicle. If radical pruning is done, flowering in the coming year is unlikely . After winter, you can cut back frostbitten shoots to the ground.
The right time to prune your hydrangea is immediately after peak bloom. Since these hydrangea species begin forming flower buds shortly after blooming, in late summer and early fall, it is important to cut them back as soon as the flowers begin to wilt in mid-summer. This way, you can prune the shrub before it begins to put on the flower buds that will develop into next year’s flowers. Simply pinch off the flower spikes about 15 to 20 inches below the flower set.
Tip: If you miss this time, simply postpone pruning until next year. Hydrangeas do not need to be pruned every year, so this is not a problem.
Has your hydrangea grown too tall or too wide and you want to reduce it significantly? If so, you can cut off half of the branches the first year and the other half the second year after flowering. This way you will still have flowers on your shrub in both years. You can also cut back the whole plant at once, but then you will not have flowers the next year.
When the hydrangea is a few years old, it begins to form fewer flowers. That is why it is useful to rejuvenate the bush every two to three years. You can encourage flower growth by removing up to 1/3 of the oldest shoots. For thicker shoots, you will probably need pruning shears. Cut these older shoots back to ground level. The newly formed branches will not bloom the first year, but will bloom in subsequent years.
Tip: Hydrangea macrophylla garden hydrangea is the variety whose buds are most damaged by frost. If you tie the branches together and wrap them with burlap, the plant can survive the winter well. Remove the burlap when the buds begin to swell.
Pruning group 2: Hydrangeas that bloom on new wood.
Hydrangeas that bloom on new wood, such as snowball hydrangea ‘Annabelle'(h. arborescens)and panicle hydrangea (h. paniculata), are very easy to prune because they sprout new buds after pruning in the spring. They even tolerate radical pruning quite well.
If you want to prune your group 2 hydrangea, you should choose a time before budbreak for this, which is late February or March. Do you want a nice compact plant? Cut all the shoots to 20-30 cm above the ground. Do you want the plant to grow a little taller? Then simply cut off only the dried flowers.
Snowball hydrangea (Hydrangea arborescens) will produce much larger flowers if it is cut back heavily to the ground each year, but many gardeners opt for smaller flowers on sturdier stems. In such cases, pruning should be done in the fall to allow the plants to develop vigorous shoots before flowering. Light pruning is also possible at other times of the year, except just before flowering in spring and early summer.
The branches of some hydrangeas often fall over under the weight of their flowers, especially after heavy rain. One way to prevent this toppling is to prune the stems back to a height of 45 to 60 inches to provide a stable framework for new growth.
Pruning Hydrangea: Summary
In general, varieties that bloom on the old wood should be pruned immediately after flowering. Those that bloom on new wood should be pruned before new growth begins in the spring. Always remove dead, damaged or diseased shoots first when doing routine pruning . When shortening shoots, cut back to just above a pair of healthy buds. Frozen shoots can be cut back to live wood after winter.