How to Prune Hydrangeas: When and How to Cut Each Type

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At a glance

Step one: identify your hydrangea

Every Extension guide on hydrangea pruning starts at the same point: know which species you have. UNH Extension and a University of Georgia Extension Master Gardener guide both stress identifying the species first, because pruning at the wrong time removes flower buds. Use the flower shape, the leaves and the stems to tell them apart.

For a fuller guide to each species, including soil pH and flower color, see hydrangea care by species.

Old wood vs. new wood: why timing matters

Old-wood hydrangeas form next year's flower buds in late summer and early fall, in August and September per University of Illinois and University of Minnesota Extension. UNH Extension notes the buds sit at the tips of stems on the previous year's wood and spend the winter there. If you cut those stems back in fall, winter or early spring, you remove the flowers before they open. That's why University of Illinois Extension advises pruning old-wood types as soon as possible after bloom and by August 1 at the latest.

New-wood hydrangeas form flower buds on shoots that grow in spring of the same year. Cutting them back during dormancy costs nothing, because the flowers haven't formed yet. University of Illinois Extension cautions that drastic cutting every year can weaken the plant, and suggests hard pruning every other or every third year.

Reblooming bigleafs (sold under names like Endless Summer) set buds on old wood and can also flower on new growth, so per Illinois Extension they can still bloom if winter kills the old-wood buds. Clemson HGIC notes the first flush usually comes from old wood, so do any needed pruning right after that first bloom.

How to prune panicle and smooth hydrangeas (new wood)

Do this in late winter or early spring, before the buds begin to grow. Clemson HGIC, UNH Extension and University of Minnesota Extension all give this window; Minnesota also allows fall pruning of panicle types.

Smooth hydrangea (H. arborescens)

1. Cut out any dead stems at the base.
2. Cut the remaining stems back to a pair of healthy buds. UNH and University of Minnesota Extension say established plants can be cut to the ground in spring; the RHS suggests a framework about 10 inches high, or about 2 feet where more height is wanted.
3. Choose the height based on how floppy the plant gets. Per UNH Extension, unpruned old stems still flower but the flowers are small; hard pruning gives larger heads, which may need support. If stems sprawl every summer, see staking floppy plants.

Panicle hydrangea (H. paniculata)

1. Remove dead, crossing and weak, spindly stems.
2. Cut last year's stems back to a pair of healthy buds, about ¼ inch above them, keeping a permanent framework of branches (RHS, UNH Extension). Cut harder for larger flower heads on strong upright stems.
3. To reduce size, UNH Extension suggests removing a few branches in spring.
4. Tree-form panicles: keep the single trunk and prune the head the same way, back to healthy buds on the main framework, and remove any shoots that sprout from the trunk or the base.

Species-level care for both is in panicle hydrangea care and smooth hydrangea care.

How to prune bigleaf, oakleaf and climbing hydrangeas (old wood)

These need very little pruning. Do whatever pruning they need in the few weeks after the flowers fade. University of Illinois Extension sets August 1 as the latest date and University of Minnesota Extension says to finish before August, so the plant has time to set next year's buds.

1. Deadhead after bloom. Cut each spent flower stem back to a pair of healthy buds or leaves below the flower head. For mopheads in cold areas, the RHS suggests leaving the dead heads on over winter to protect the buds below and removing them in early spring.
2. Thin, don't shear. On a crowded shrub, cut one or two of the oldest stems at the base, as the RHS advises. Clemson HGIC says to remove no more than a third of the plant's total growth. Shearing the whole shrub to one height removes flower buds across the entire plant.
3. Control size the right way. If a bigleaf hydrangea always outgrows its space, pruning will only cost you flowers. A smaller cultivar or a different spot is the lasting fix; see hydrangea cultivars by type.
4. In spring, remove only dead wood. Per UNH Extension, wait until new growth appears so you can see which stem tips survived the winter, then cut ¼ inch above the first set of live buds. Live stems are green inside; cut entirely dead stems flush at the base.

Oakleaf hydrangea is grown for its shape and its peeling bark as much as its flowers. Clemson HGIC prunes it soon after its June bloom to keep size and shape; UNH and the RHS limit routine pruning to dead or damaged stems. Climbing hydrangea only needs over-long shoots shortened right after flowering, per the RHS and UNH Extension.

When to prune hydrangeas: timing by zone

These months are approximate, derived from the Extension rule of late winter before growth starts. The plant itself is the better signal: prune new-wood types before buds open, and prune old-wood types as soon as the flowers fade. The site's pruning calendar lists the right window for hydrangeas alongside other shrubs.

What to do in fall

For old-wood types, the answer is nothing beyond removing broken or diseased stems. The flower buds for next summer are already on the stems. Spent flower heads can stay on through winter, then come off in spring once you can see the buds. New-wood types can be cut back after fall frost, per NC State Extension, and University of Minnesota Extension allows fall pruning of panicle types; late winter works just as well. If a bigleaf hydrangea has leaves and no flowers, the cause is often winter bud damage or pruning at the wrong time; see why hydrangeas don't bloom.

Renovating an overgrown hydrangea

A neglected shrub that's a mass of old, weak stems can be renewed without losing all its flowers by spreading the work over three years. For large, old panicle hydrangeas, UNH Extension cuts a third of the oldest stems to the ground in spring the first year, half of the remaining old stems the second year, and the rest the third year.

Smooth hydrangeas tolerate being cut to the ground in late winter and still bloom that summer. The RHS notes a bigleaf hydrangea can be renovated by cutting all stems at the base, but that removes all flowers for that summer; for climbing hydrangea it recommends staggering drastic pruning over three or four years.

Tools and how to make the cut

• Bypass pruners for most stems; they make clean cuts. The site compares models in best bypass pruners.
• Loppers or a small pruning saw for thick old stems at the base.
• Cut placement: about ¼ inch above a bud or pair of buds, as UNH and University of Minnesota Extension advise. Don't leave long stubs.
• Clean the blades with rubbing alcohol or a bleach solution, as the University of Georgia Extension guide suggests, especially when removing diseased wood.

Common mistakes

Frequently asked

What month is best to prune hydrangeas?

It depends on the type. Prune panicle and smooth hydrangeas in late winter or early spring, roughly February to April depending on your zone. Prune bigleaf, oakleaf and climbing hydrangeas in the weeks right after they finish blooming, and finish by August 1, per University of Illinois Extension.

When should you prune a Limelight hydrangea?

'Limelight' is a panicle hydrangea, so it blooms on new wood. Prune it in late winter or early spring before growth starts, cutting last year's stems back to a pair of healthy buds and removing weak ones. University of Minnesota Extension lists 'Limelight' among its favorite panicle hydrangeas. Pruning then doesn't reduce that summer's bloom.

Do you cut off dead hydrangea blooms?

You can. On bigleaf types, cut spent flowers back to a healthy pair of buds right after bloom, or leave the dried heads on through winter, as the RHS suggests for mopheads, and remove them in early spring. On panicle and smooth types, old flower heads come off with the late-winter pruning.

Should I cut off brown hydrangea blooms in winter?

It isn't necessary. The RHS suggests leaving mophead flower heads on over winter to help protect the buds below. If you remove them from a bigleaf hydrangea, cut just below the flower head only. Cutting further down the stem removes the buds for next summer's flowers.

What happens if you don't cut back hydrangeas?

Bigleaf, oakleaf and climbing hydrangeas generally do fine with little or no pruning. Panicle and smooth hydrangeas still bloom unpruned, but per UNH Extension old stems of smooth hydrangea produce small flowers, and the RHS notes both flower more prolifically when pruned back annually to a framework.

How do you prune a hydrangea tree?

Most hydrangea trees are panicle hydrangeas trained to a single trunk. In late winter or early spring, cut last year's shoots back to healthy buds on the main framework of the head, remove crossing shoots, and remove any shoots from the trunk and base.

When should you prune an oakleaf hydrangea?

Right after it flowers, because it blooms on old wood; Clemson HGIC notes it blooms in June. Oakleaf hydrangeas need very little pruning. Remove dead, crossing or misplaced stems only, so you keep the plant's natural shape and peeling bark.

Sources

1. Pruning hydrangeas, University of Minnesota Extension
2. Pruning Hydrangeas (fact sheet), UNH Extension
3. Pruning Hydrangeas, Clemson Cooperative Extension HGIC
4. The Comprehensive Guide to Pruning Hydrangeas, University of Georgia Extension, Fulton County (Master Gardener column)
5. For showy blooms, pruning hydrangeas is all about the timing, University of Illinois Extension
6. Pruning Tips for Hydrangeas, N.C. Cooperative Extension, Macon County
7. Hydrangea pruning, Royal Horticultural Society

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