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

Hydrangeas are popular for their lush blooms, gorgeous colors, hardy leaves, and low-maintenance personalities. These perennials, which do best in well-drained soil in USDA zones 5 to 9, are happiest with 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 (the stems the plant has produced in the current season) or on old wood (the growth from the previous season). Prune at the wrong time, and you could inadvertently cut into next season's flowers.

Ahead, experts share their tips for when and how to prune the most popular 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 in 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 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 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 fall, winter, or spring, you'll remove the buds before they get a chance to bloom.

"For optimal blooms, this green-stemmed hydrangea should be pruned 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.

Clean dead stems by 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

Bigleaf hydrangeas (Hydrangea macrophylla), including the popular lacecap and mophead varieties, come in blue, pink, and purple shades, with thick, shiny leaves, and bloom on old wood. Mophead hydrangeas produce large, ball-shaped flower clusters, while lacecap hydrangeas produce flat and delicate flower clusters.

• 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 winter.
• If a plant is overgrown, prune back about one-third of the older stems almost to the ground.

How to Prune Oakleaf Hydrangeas

Oakleaf hydrangeas (Hydrangea quercifolia) 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

Smooth hydrangeas (Hydrangea arborescens) are known for being fast growers. One popular variety, Annabelle, has big flowers that are actually made up of many small individual blooms. The blooms start out as lime-green and transition to a beautiful white throughout the season.

• 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 next year's buds.
• To reduce plant size, cut down all stems to the ground in late winter or early spring before new stem growth, says Becker.
  

How to Prune Panicle Hydrangeas

Panicle hydrangeas (Hydrangea paniculata), which include peegee and limelight varieties, are most often cone-shaped and sharply pointed. It comes in many shapes and sizes, 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. You can also prune after blooming.
• Pruning hard in late winter will encourage vigorous growth of new stems, says Becker.

How to Prune Mountain Hydrangeas

Mountain hydrangeas (Hydrangea serrata) are a smaller shrub with narrower, pointed leaves. The flower color for this variety is affected by soil pH—it produces lilac to pink flowers in alkaline soil and blue blossoms in acidic soil.

• Mountain hydrangeas bloom 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 to manage the size of the plant.