Many people get confused about when to prune hydrangeas. It is essential to know which species or cultivar you have to determine when to prune.
Bigleaf hydrangeas (Hydrangea macrophylla) set flower buds on old wood, which develop in late summer and fall; therefore, pruning should be done immediately after flowering. Be sure to remove only a third of the total growth of the plant. The cultivars in the Endless Summer® series are an exception to this rule. The first flush of flowers of these cultivars usually bloom on old wood; therefore, any necessary pruning should be done immediately after blooming. Flower buds will then form on new wood, and the Endless Summer® hydrangeas will repeat bloom throughout the summer.
The panicle (Hydrangea paniculata) and smooth hydrangeas (Hydrangea arborescens) develop flowers on new wood produced during the current growing season. Since they develop flowers on new growth, they can be pruned either in late winter or early spring while the plants are dormant and before new growth begins.
Oakleaf hydrangeas (Hydrangea quercifolia) flowers develop on old wood from last year’s growth. It blooms in June; therefore, to maintain a desired size and shape, they should be pruned soon after flowering. This will allow these beautiful native hydrangeas time to develop flower buds for the following year.