Learn When to Prune Hydrangeas for Big, Showy Blooms

Courtesy Sheila Head

Hydrangeas are beloved summer-blooming shrubs. However, getting them to flower can be a challenge for gardeners, partially due to pruning mistakes. “Pruning hydrangeas can be confusing because each species should be pruned at a different time of the year,” says Ken Johnson, University of Illinois Extension horticulture educator. “The five common hydrangea can be divided into two groups for pruning purposes: those that bloom on old wood and those that bloom on new wood.”

Hydrangeas That Bloom on Old Wood

The first step is identifying what kind of hydrangea you have. Then you can determine when you should prune it. Timing is everything!

Hydrangeas that bloom on old wood start to develop their flower buds for the next year in August and September. Therefore, if you are going prune them, try to finish as soon as possible after they are done blooming—by August 1 at the latest. Wait any longer, and you risk removing the developing flower buds. That means no blooms next summer.

The three commonly cultivated Hydrangea species that flower on old wood are:

• Bigleaf, mophead, and lacecap hydrangea, Hydrangea macrophylla
• Oakleaf hydrangeas, Hydrangea quercifolia
• Climbing hydrangea, Hydrangea anomala

There are some varieties of H. macrophylla that are reblooming, or remontant, meaning these cultivars will produce flower buds on both old and new wood. If the buds are nipped by frost or killed off during a harsh winter, all hope is not lost. The plant can still bloom on new wood. Examples of these types of hydrangeas are the Endless Summer, Let’s Dance series, and Tuff Stuff hydrangeas. Psst—check out the biggest blooms for your flower garden.

Courtesy Amy Evonluk

Hydrangeas That Bloom on New Wood

Hydrangeas that bloom on new wood produce their flower buds on the current season’s new growth. These plants can be pruned from late winter to early spring. They also can be heavily cut back in the fall. This may weaken the plant, however. So consider limiting pruning every other year or every three years to ensure your hydrangea’s health and vigor.

The two commonly cultivated hydrangea species that bloom on new wood are:

• Hydrangea paniculata, which are commonly called panicle or PG hydrangea, such as Pinky Winky and Limelight.
• Hydrangea arborescens, commonly called smooth hydrangea, such as Incrediball.

Keep in mind that maintenance pruning, which includes removing diseased and dead wood as well as deadheading old flower blossoms, can be done at any time. Pay attention to timing your hydrangeas will produce beautiful blooms for years to come! Here’s more tips to help you become a pruning pro.