Knowing when and how to prune hydrangea plants will ensure that your hydrangeas have vigorous growth and impressive blooms. A hydrangea that’s pruned incorrectly may fail to bloom.
There are simple rules you can follow when it comes to pruning hydrangeas, depending on whether they bloom on new growths or old wood.
To successfully prune your hydrangeas each time, I’ll walk you through everything you need to know about when and how to cut hydrangeas.
Pruning Hydrangeas in Summer
Several hydrangea varieties bloom only on old wood including the bigleaf hydrangea, mountain hydrangea, climbing hydrangea, and the oak-leaf hydrangea.
These bloom on the previous year’s growths, so cutting down these growths in spring, for example, means you’re practically cutting down dormant buds, leaving your hydrangea flowerless for the season.
The rule is to prune these hydrangeas that bloom on old wood just as blooms start to fade away in summer. The earlier you prune after flowering, the better. The shrub can recover sooner and produce more impressive blooms next season.
Also remove any dead stems or stems that are weak or straggly by cutting them down to the base. To improve the vigor of the hydrangea and produce more abundant blooms next season, remove a few of the oldest stems.
You can also cut some of the tallest stems to get your hydrangea back to a manageable size.
Pruning Hydrangeas in Winter
Panicle and smooth hydrangeas bloom on new wood, therefore, these require pruning in late winter, just before the plant awakens from dormancy and it’s metabolism springs into action again.
These hydrangeas need to put out new growth and blossom in the same season, so cutting them back before they put out new buds is essential.
Compared to hydrangeas that bloom on old wood, these hydrangeas bloom later in the season — they start blooming in mid-summer and continue to bloom throughout fall until the frost sets in.
There are two ways to go about pruning these late bloomers:
- You can cut them down all the way to the base
- Leave a framework of old growths (18 to 24 inches tall)
Cutting late blooming hydrangeas to the base will result in much larger blooms. However, leaving a framework of old growths will prevent flopping (branches falling over the weight of blooms).
A potential problem with hydrangeas that are pruned in late winter or spring is a late frost damaging new growths.
In case of frost damage to live, healthy wood, prune back to the first undamaged pair of buds. Stems that trail onto the ground, straggly or otherwise weak stems should also be removed.
Therefore, prune back hydrangeas that bloom on old wood immediately after blooming. Prune hydrangeas that bloom on new wood in late winter, before they shoot out any new growths.
Whenever you’re pruning or even just deadheading hydrangeas, you should use sterilized blades to prevent any transfer of fungal, bacterial, viral diseases or even pests.
Can You Cut Hydrangeas to the Ground?
You can cut hydrangeas to the ground, especially if you’re looking to reinvigorate a hydrangea that’s doing poorly, or simply you want to stimulate the production of larger blooms on hydrangeas that should be pruned in winter.
These hydrangeas can be cut down to the ground yearly. Hydrangeas that bloom on old wood, however, may skip one or two seasons of blooming if they’re cut all the way down to the ground.
Therefore, it’s better to stagger any drastic pruning over 3 years to avoid bloomless seasons.
Do You Deadhead Hydrangeas?
Yes, I deadhead my hydrangeas throughout the blooming season after blooms fade. Deadheading is different from pruning.
When you’re deadheading, you’re simply removing old blooms with a part of the stem attached to them. This is where usually mistakes happen.
Spent hydrangea blooms should only be cut just above the first set of fresh leaves. This will ensure that any eventual buds stay on and continue to produce new flowers.
And this is the rationale of deadheading — to stimulate the production of new flowers. And not only new flowers, but bigger ones as well.
Another benefit of deadheading hydrangeas — beyond the aesthetical one — is that removing spent blooms will improve aeration around the leaves. This in turn helps reduce the occurrence of fungal diseases.
I’ve also seen gardeners who don’t deadhead hydrangeas going into winter. Their rationale is to provide further insulation and frost protection to these shrubs.
Since I always set up adequate winter protection to hydrangeas that may have trouble with frosty winters, I see no extra benefit of leaving spent blooms on the plant.
But I also don’t see any downsides to this method either, so you can go either way.
What Happens if You Don’t Prune Hydrangeas?
Hydrangeas don’t require intensive pruning, but a trim here and there is certainly beneficial, if done correctly.
If you don’t prune hydrangeas for years on end, usually you can expect one of three things to happen:
- Hydrangeas grow tall and leggy, reaching their maximum size at maturity
- Their bloom production suffers both in quality and in quantity
- The plant can lose its vigor and strength because of a surplus of old canes
Therefore, regular pruning will help your hydrangea grow bushy and remain at a manageable size. It also helps the production of more spectacular blooms. And lastly, pruning will stimulate more vigorous growth and development.
Hydrangea plants are easy to prune and the timing of the pruning is everything. Not all hydrangeas can be pruned at the same time. Cut your hydrangeas at the wrong time and you risk losing blooms for the entire season.
When cut correctly, hydrangeas will grow bushier, produce more blooms and generally grow more vigorously.
You can even cut back some hydrangeas all the way to the base. Canes that are dead or diseased should always be cut down to the soil line.
If you know which type of hydrangea you’re growing, remember the rule — hydrangeas that grow on old wood, should be cut after flowering, those that grow on new wood, should be cut in late winter.