How to Prune Every Type of Hydrangea (and When to Do It) (2024)

Hydrangeas are easily recognizable by their lush blooms and hardy leaves, and are popular for their gorgeous colors, delicate shapes, and low-maintenance personalities. These perennials, which do best in well-drained soil in USDA zones 5 to 9 and grow from 3 to 6 feet tall, are happiest with a gentle pruning to keep their shape—but since not all hydrangeas boast the same bloom schedule, knowing when to get out your shears is critical.

Different types of hydrangeas flower in one of two ways: either on new wood, which are the stems the plant has produced in the current season, or on old wood, which is the growth from the previous season. Prune at the wrong time, and you could be inadvertently cutting into next season's flowers.

We asked the New York Botanical Garden (NYBG) and David Becker of The Farm at Green Village for help explaining how to properly prune the most common types of hydrangeas: bigleaf, oakleaf, panicle, smooth, and mountain.

When to Prune Hydrangeas That Bloom on New Wood

Hydrangeas that bloom on new wood include smooth hydrangeas and panicle hydrangeas. These hydrangeas set their flower buds in spring and bloom a few weeks later, during the following summer. "When to prune these woody-stemmed hydrangeas is not as critical as [with old wood] varieties, as long as you avoid pruning when the flower buds are opening," says Becker. Trim in early spring, before the flowers begin to bud, or after the plant has finished flowering. "If you are just doing some shaping of plants that are too tall, you can sheer off the ends of each branch," says Becker.

For a more aggressive pruning, trim the branches before the growing season starts. "If you need to do a severe pruning to rejuvenate a spindly shrub, you can cut all the branches back to about a foot above the ground in late winter or early spring when it's still dormant," says Becker. "This will cause the plant to produce lots of fresh new growth, and you'll still see flowers later that same year. Generally, you can remove about one-third of the plant without doing any damage to the plant."

When to Prune Hydrangeas That Bloom on Old Wood

Hydrangeas that bloom on old wood, including bigleaf, oakleaf, and climbing hydrangeas, produce flower buds during the later part of the summer season. If you prune these shrubs in the fall, winter, or spring, you'll remove the buds before they get a chance to blooms.

"For optimal blooms, this green-stemmed hydrangea should bepruned soon after the flowers have faded in late summer—then the shrub will have a chance to produce new growth where next year's flower buds will form," says Becker.

To clean out dead stems, Becker recommends gently scratching each stem. If the bark comes off to reveal green, you're holding a live, able-to-flower branch. If the stem is brown underneath the bark, you've found an old stem that can be removed.

How to Prune Bigleaf Hydrangeas (Hydrangea macrophylla)

Bigleaf hydrangeas, including the popular lacecap and mophead varieties, come in blue, pink, and purple shades, with thick, shiny leaves, and bloom on old wood. Mophead produces large, ball-shaped flower clusters, while lacecap's clusters are flat and delicate.

• Trim bigleaf hydrangeas back to a set of healthy buds after the flowers have faded, in late summer, before the plant begins to go dormant.
• Use sharp, clean trimmers to cut stems just higher than a pair of leaves, says Becker.
• For a heavier prune, remove the gray, older. or dead stems during the winter.
• If a plant is overgrown, prune back about one-third of the older stems almost to the ground.

How to Prune Oakleaf Hydrangeas (Hydrangea quercifolia)

Oakleaf hydrangeas have leaves that look like they belong on red oak trees, and flowers that open white and then turn pink. The hydrangea, which grows on old wood, doesn't need much pruning.

• If your oakleaf is outgrowing its dedicated space, cut back no more than one-third of the stems after the plant flowers in June or July, says Becker.
• Weak and dead stems can also be removed in late winter or early spring.

How to Prune Smooth Hydrangeas (Hydrangea aborescens)

Smooth hydrangeas' leaves are thinner than mophead's and lacecap's. One variety, Annabella, has big flowers that are actually made up of many small individual blooms, which start out green but turn white a few weeks later.

• Smooth hydrangeas bloom on new wood, so the best time to prune is early spring, before any flower buds have appeared
• Pruning after flowering will not affect the next year's buds
• "To reduce plant size, cut down all stems to the ground in late winter or early spring, prior to new stem growth," says Becker.

How to Prune Panicle Hydrangeas (Hydrangea paniculata)

This white species, which includes peegee and limelight varieties, is most often cone-shaped and sharply pointed. It comes in many varieties, from small shrubs to small trees. Its leaves are rough and thin.

• Panicle hydrangeas bloom on new wood
• Prune in early spring, before the plant starts flowering, or after blooming
• "Pruning hard in late winter will encourage vigorously growing new stems," says Becker.

How to Prune Mountain Hydrangeas (Hydrangea serrata)

Mountain hydrangea—sometimes called Tree of Heaven—has a similar look to Mophead, but it is a smaller shrub with narrower, pointed leaves. The flower is affected by a soil's pH: It produces lilac to pink flowers in alkaline soil and blue blossoms in acidic soil.

• Mountain hydrangea blooms on old wood
• Cut out dead or weak stems in late winter or early spring (check for brown stems under the bark to make sure you aren't removing live branches)
• "Remove old flowering stems as soon as the blooms fade in summer," says Becker.
• Trim stems by one-third just before September, as needed, to manage the size of the plant