How to Prune Hydrangeas: Fall Maintenance Tips

Pruning hydrangeas confuses more gardeners than almost any other flowering shrub. Some sources say prune in fall, others insist you'll ruin next year's blooms. Both are right, depending on which hydrangea you're growing.

The confusion comes from the fact that different hydrangea types bloom on different wood. Some flower on new growth produced in spring, while others form buds on old wood from the previous year. Prune the wrong type at the wrong time and you'll spend next summer staring at a green bush with zero flowers.

Fall pruning works perfectly for some hydrangeas and is absolutely wrong for others. You need to know which type you have before you start cutting, or you'll be gambling with next year's bloom display.

Here's how to figure out if your hydrangeas should be pruned now or left alone until spring. If you should prune hydrangeas now, we'll cover how to get it right.

The Risks of Pruning in Fall

The biggest risk when you prune hydrangeas in fall is cutting off next year's flowers without realizing it. If you don't know which type of hydrangea you have, there's a good chance you're looking at a bigleaf variety that blooms on old wood. Those dried flower heads you're tempted to remove have next summer's blooms already formed just below them.

Even gardeners who think they know which hydrangea they have sometimes get it wrong. Garden centers may mislabel plants, or previous homeowners don't leave records, and many people inherit hydrangeas when they buy houses. Unless you're absolutely certain you have a smooth or panicle hydrangea, fall pruning is risky.

The safer approach is waiting until spring when you can better identify the hydrangea type based on its growth pattern and flower buds. But if you know for certain you have a new-wood bloomer, you can prune hydrangeas in fall without problems.

Which Hydrangeas to Prune in Fall

Smooth hydrangeas (Hydrangea arborescens) bloom on new wood, so fall pruning won't affect next year's flowers. These are the large types that produce huge blooms in summer on the current season's growth.

You can cut smooth hydrangeas back hard in fall or winter. They'll send up new stems in spring that flower by mid-summer. You can wait until late fall after the first hard frost before pruning these, since the dried flower heads provide some winter interest.

Panicle hydrangeas (Hydrangea paniculata) also bloom on new wood and can be pruned in fall. These are the cone-shaped flower types. The flowers start white or greenish and often turn pink as they age.

Fall pruning keeps panicle hydrangeas from getting too large and floppy. Cut them back by about one-third to maintain a manageable size. If it is getting out of control, you can prune a panicle hydrangea harder without sacrificing flowers.

The benefit of fall pruning for these types is simply convenience and aesthetics. You're usually cleaning up the garden anyway, and removing those large dried flower heads makes beds look tidier through winter. But you can also wait until early spring if you prefer, as it won't make much difference to the plant.

Which Hydrangeas Not to Prune in Fall

Bigleaf hydrangeas (Hydrangea macrophylla) bloom on old wood, meaning next year's flowers are already formed on this year's stems. These include mophead and lacecap types with blue, pink, or white flowers.

The only fall maintenance bigleaf hydrangeas need is removing completely dead/diseased wood (stems that are brown and brittle all the way through). Live stems should be left alone until you can see which buds survived winter, usually evident by late spring.

Oakleaf hydrangeas (Hydrangea quercifolia) also bloom on old wood and should not be pruned in fall. These native hydrangeas typically have white flowers and distinctive oak-leaf-shaped foliage that turns burgundy in fall.

Leave oakleaf hydrangeas alone until right after they flower in summer. The dried flower heads and peeling bark provide winter interest, and the old stems protect flower buds from cold damage.

Climbing hydrangeas (Hydrangea anomala petiolaris) rarely need pruning at all, but if you must prune them, never do it in fall. These slow-growing vines bloom on old wood and can take years to recover from hard pruning. Let them grow undisturbed through winter.

Reblooming hydrangeas like 'Endless Summer' technically bloom on both old and new wood, but they still shouldn't be pruned in fall. You'll get more flowers if you leave the old stems intact through winter. The new wood blooms appear later and are less prolific than flowers on old wood.

How to Prune

For hydrangeas that bloom on new wood (smooth and panicle types), wait until late fall after plants have gone fully dormant. You'll know they're dormant when leaves have dropped and stems show no green growth.

Use sharp, clean bypass pruners to make clean cuts. For larger stems on older plants, you may need to switch to loppers. Make cuts at a slight angle just above a node (the bump where leaves or buds emerge from the stem).

Remove dead, damaged, or crossing stems first when you prune these hydrangeas. These should come out regardless of hydrangea type since they don't contribute anything and can harbor pests or diseases over winter.

For smooth hydrangeas, cut back to around 12 inches from the ground. You can go lower if you want, but you don't have to for strong growth. Panicle hydrangeas don't need to be cut as low. Remove about one-third of the height to keep plants compact, or cut back further if they've gotten too large. Focus on removing the thinnest, weakest stems to encourage stronger growth.

Always step back and look at the overall shape as you prune. The goal is a balanced plant with good air circulation through the center. Remove stems growing toward the center of the plant to open up the interior.

For hydrangeas that bloom on old wood, fall "pruning" means only removing obviously diseased stems. If you're not sure whether a stem is dead, leave it alone. You can always prune it in spring once you know for certain, but you can't undo fall pruning that removes live wood with flower buds.

Cleaning Up

Collect all pruned material and dispose of it rather than composting, especially if you saw any signs of disease during the growing season. Powdery mildew and leaf spot can overwinter in plant debris.

After pruning, apply a layer of mulch around the base of hydrangeas. This insulates roots during temperature swings and helps retain moisture. Keep mulch a few inches away from stems to prevent rot.

Don't fertilize after fall pruning. You want plants going dormant, not pushing new growth that won't survive winter. Save feeding for early spring when new growth emerges.

If you have types you're not supposed to prune in fall, but they look messy, resist the urge to prune hydrangeas and tidy them up. Those dried flowers and old stems are doing important work protecting next year's blooms. You can clean them up in spring once the danger of hard freezes has passed.