How and When to Prune Hydrangeas

Every gardener needs sharp, effective pruning tools. There’s a variety of tools you can use, depending on the scale of the job.

Experts recommend these tools for pruning hydrangeas:

• Hand pruners are ideal for cutting stems up to 5/8-inch diameter. There are two styles: anvil types that crush stems and bypass pruners with a ratcheting mechanism that gives a cleaner cut. Most gardeners have several pairs of bypass pruners that they keep at hand to trim shrubs and perennials. If you’re always misplacing your pruners, try a scabbard, or leather holster that you attach to your belt and carry your pruners with you.

• Pruning snips are handy if you’re trimming blooms from flowering hydrangeas. The sharp blades cut cleanly through tender stems. Snips are not recommended for thicker, woody stems.

• Loppers are the tools you need to tackle thicker branches, and they’re most effective for branches 1- to 1 1/2-inches in diameter. Loppers are essentially long-handled, heavier-duty pruners, and just like with hand shears, bypass styles are the most effective and will make your pruning tasks easier.

• Pruning saws help when the branches are too thick for hand pruners and loppers. In the garden tool aisle, look for bow style, D-handled and folding pruning saws. A folding saw is the most convenient for gardeners to carry and they are effective in tackling branches that are too cumbersome for loppers.

• Hedge shears are optional, because most hydrangeas are not trimmed into formal hedges. However, hedge shears are sharp and useful if you’re shaping the shrubs into a form.

Remember your gardening gloves when you’re pruning shrubs. They’ll protect your hands from sharp stems and scratchy branches.

Before you prune your hydrangeas, make sure you know the type you have in your landscape. Hydrangeas bloom on either “old wood” and set next year’s flower buds immediately after flowering, or on “new wood.” The latter means that flower buds grow on new stems each spring.

There’s also remontant (“reblooming”) hydrangeas that bloom on both old and new wood. ‘Endless Summer’ is a popular brand of reblooming hydrangea.

Following are the main types of hydrangeas and the best time to prune them:

• Mophead (also called macrophylla or “big leaf”) hydrangeas bloom on old wood. Prune hydrangea macrophylla to remove dead and weak stems and to keep the plant neat. Thinning out older stems encourages new growth. Best time to prune hydrangea macrophylla is right after they finish blooming and before they set next year’s blooms. The old growth helps protect the plants in cold winter climates.

• Mountain hydrangeas (called Hydrangea serrata) are like mopheads but are tougher in extreme climates. They bloom on old wood and are best pruned right after they finish blooming. Many mountain hydrangea cultivars are grown for patios and small spaces and won’t need much pruning.

• Smooth hydrangeas (also called arborescens and known as ‘Annabelle’ type) bloom on new wood. Prune smooth hydrangeas in late winter or early spring before they set buds on new growth. If the plant is several years old, you can hard prune these to about 12 to 18 inches from the ground. This will prevent floppy stems in mid-summer. If you like the look of a full shrub, there’s no need to prune other than to eliminate dead or diseased branches.

• Panicle hydrangeas (called peegee and hardy hydrangea) bloom on new wood. One of the most popular cultivars is ‘Limelight.’ Prune panicle hydrangeas in late winter and early spring just as the plant breaks dormancy. When pruning, you can remove up to one-third the volume of a mature panicle hydrangea shrub.

• Oakleaf hydrangeas, Hydrangea quercifolia, are native to the southeastern United States. Oakleaf hydrangeas bloom on old wood and don’t often need pruning other than to maintain structure and remove old stems. Prune oakleaf hydrangeas immediately after flowering in summer.

• Climbing hydrangeas are, like oakleaf hydrangeas, native to the southeastern United States. The deciduous vines bloom on new wood and are best pruned in late winter and very early spring.

• When you’re ready to prune hydrangeas, make sure your tools are sharp and that you’re wearing gardening gloves. Experts recommend wearing long sleeves when you’re pruning, to protect your arms from scratchy branches.

• When you’re pruning shrubs, it’s important to avoid spreading diseases from plant to plant. For this reason, it’s a good idea to carry either alcohol or disinfecting wipes with you and routinely wipe down your pruning shears and loppers in between plants.

• Big leaf and mountain type shrubs benefit the most from thinning. This means using loppers to get into the interior of the shrub and remove stems to improve air circulation.

• Deadheading, simply removing the blooms at the branch tips, can be done any time of the year on any type of hydrangea. Deadheading makes for a tidy looking garden.