Summer pruning hydrangeas requires precision, differing significantly from heavy dormant season shaping. Unlike winter maintenance, summer cuts must be made carefully to ensure the shrub’s health. Incorrect timing or placement of a cut can inadvertently remove the buds that produce the next season’s flowers. To guarantee a spectacular display the following year, understanding the specific growth habits of your hydrangea variety is essential.
Why Identifying Your Hydrangea Matters Most
The primary factor determining how to prune your hydrangea is whether it blooms on “old wood” or “new wood.” This distinction dictates how much pruning the plant can handle without sacrificing future blooms.
Old wood bloomers, such as Bigleaf (Hydrangea macrophylla) and Oakleaf (Hydrangea quercifolia), develop flower buds on stems that grew the previous summer. These buds form in late summer or early fall, so substantial pruning then removes them, leading to a lack of flowers the following season. New wood bloomers, including Panicle (Hydrangea paniculata) and Smooth (Hydrangea arborescens) types, produce flowers on growth that emerges in the current spring. Since flower buds have not yet formed when summer pruning occurs, these types are more forgiving of cuts made during the active growing season. This knowledge establishes the strict boundaries for summer maintenance.
The Primary Summer Task: Deadheading Spent Blooms
Deadheading, the removal of faded or spent flowers, is the primary summer activity for all hydrangea varieties. This practice improves the plant’s aesthetic appearance by removing brown or drying flower heads. For reblooming varieties, deadheading can also encourage a second flush of flowers by diverting the plant’s energy away from seed production.
Use clean, sharp bypass pruners to remove the spent flower just above the first healthy set of leaves or visible side bud below the bloom. Cutting back to a healthy growth point ensures the plant seals the wound quickly and avoids leaving a stub that could invite disease. This technique focuses only on the flower structure.
Step-by-Step Summer Pruning by Hydrangea Variety
Old Wood Bloomers
For old wood bloomers, such as Bigleaf and Oakleaf types, summer pruning must be kept to an absolute minimum. The only recommended action is deadheading, which removes only the bloom itself. Be careful to snip the stem just above a pair of leaves, avoiding cuts into the older, thicker wood. Removing any significant portion of the main branch structure during summer eliminates the buds set for the next year. If the plant requires rejuvenation or major size reduction, reserve that work for immediately after blooming in early summer or during the winter dormant period.
New Wood Bloomers
New wood bloomers, including Panicle and Smooth hydrangeas, allow for a more lenient approach to summer shaping. After the initial blooms fade, you can perform light shaping cuts to maintain the desired size and structure. This involves selectively shortening new stems or removing weak growth to encourage a stronger framework. While these varieties tolerate cuts well, excessive removal of foliage can stress the plant during hot weather.
The Cutoff Date: When to Stop Pruning Entirely
Establishing a strict cutoff date is the most important rule for protecting next year’s blooms on old wood varieties. Pruning must cease entirely by late July or early August in most temperate climates. This timing allows old wood bloomers sufficient time to initiate and mature flower buds before cold weather begins. Cutting these varieties after this deadline risks removing newly formed buds, resulting in a barren spring. While the precise date can vary based on local climate, using the beginning of August as a firm deadline is a safe practice.
For new wood bloomers, the timing concern is protecting the plant from winter damage. Pruning too late, especially into the fall, stimulates tender new shoots that cannot harden off before the first hard frost. These soft, immature stems are highly susceptible to freeze damage, which can weaken the overall plant structure.