Your hydrangeas are done blooming, but that doesn’t necessarily mean it’s time to prune. For bigleaf or oakleaf hydrangeas, pruning too late in the season could mean fewer flowers next year. These old-wood hydrangeas begin forming next year’s flower buds during the summer—possibly as early as August—so timing matters.
Unlike varieties that bloom on new growth, old-wood hydrangeas are generally pruned shortly after they finish flowering. And if you missed that window, it may be better to prune less, or not at all, rather than risk sacrificing next year’s display.
Here’s how to determine whether you have an old-wood hydrangea, why you should be cautious about pruning it now, and which hydrangeas follow an entirely different pruning schedule.
What Type of Hydrangea Should You Prune After Blooming?
The hydrangeas you need to be particularly careful with are varieties that bloom on old wood, meaning their flower buds develop on stems that grew during a previous season.
Bigleaf hydrangeas (Hydrangea macrophylla) fall into this category. This popular species includes mophead hydrangeas, known for their large, rounded flower clusters, and lacecap hydrangeas, which have flatter blooms. Oakleaf hydrangeas (Hydrangea quercifolia) also bloom on old wood. Oakleaf hydrangeas are relatively easy to recognize thanks to their distinctive oak-shaped leaves and cone-shaped flower clusters. Mountain hydrangeas (Hydrangea serrata) are another old-wood type. They resemble bigleaf hydrangeas and commonly produce lacecap-style flowers.
These hydrangeas don’t necessarily need to be pruned every year. But if you need to control their size or shape, or remove any dead or damaged wood, the safest time to do so is shortly after flowering.
One important caveat is that some newer bigleaf and mountain hydrangeas are reblooming varieties. These can flower on both old and new wood, making a pruning mistake less likely to eliminate an entire season of flowers.
Why You Shouldn’t Wait Too Long to Prune
Old-wood hydrangeas begin forming the buds for next year’s flowers during summer and fall. Some Extension experts recommend completing pruning before August because flower bud development begins.
If you prune healthy branches after next year’s flower buds have begun developing, you will remove those buds along with the branches. The plant itself should be fine, but you may wind up with fewer flowers the following year. Keep in mind that if your plant is healthy, an appropriate size, and has a shape you like, you can simply leave it alone.
If you’re unsure whether it’s too late to prune, a conservative approach is best. Removing less growth now can mean keeping more of next year's flowers intact.
How to Prune These Hydrangeas Without Removing Next Year’s Blooms
If you’re still within the appropriate pruning window for your hydrangea, start with clean, sharp pruning shears and take a conservative approach. This isn’t the time to dramatically cut the entire shrub to the ground.
Remove damaged growth and any stems you can confidently identify as dead. If you're unsure whether a stem is truly dead, you can wait until spring growth makes living and dead branches easy to distinguish.
A dense or crowded hydrangea can benefit from selective thinning to improve its structure and air circulation. So rather than indiscriminately shortening every branch, remove individual stems as needed.
You can also deadhead faded flowers without giving the shrub a major pruning. When deadheading, remove only the spent flower at the tip. Doing this will give the plant a neat and tidy appearance.
Above all, avoid giving old-wood hydrangeas a major late-season haircut. Removing large portions of healthy growth can remove the stems carrying next year’s flower buds. If in doubt, remember the adage—less is more.
What About Hydrangeas That Bloom on New Wood?
Not every hydrangea follows the same pruning schedule, which is why identifying your plant before cutting is so important.
Panicle hydrangeas (Hydrangea paniculata) and smooth hydrangeas (Hydrangea arborescens) bloom on new wood. Their flower buds develop on growth produced during the same growing season in which they bloom.
These hydrangeas are generally pruned in late winter or early spring, before vigorous new growth gets underway. That means there’s no need to rush outside and cut them back now just because their flowers are fading and getting crispy from the sun.
If you aren’t sure which hydrangea is growing in your yard, resist the urge to start cutting. Look at its leaves, flower shape, growth habit, and, if you know it, the cultivar name before deciding when to prune. There are a ton of great apps that help identify plants. Two I like are PictureThis and Seek.
