Pruning hydrangeas is a crucial step to ensure their healthy growth and vibrant blooms. To successfully carry out this task, it is essential to understand the different varieties of hydrangeas and their flowering cycles. This knowledge allows gardeners to precisely determine when and how to prune these shrubs to maximize their beauty.
The Different Varieties of Hydrangeas
Bigleaf Hydrangeas (Hydrangea macrophylla): This group includes both mophead and lacecap hydrangeas. They bloom on last year’s wood, meaning that their flower buds form at the end of summer or during the autumn and open the following year.
Panicle Hydrangeas (Hydrangea paniculata): These hydrangeas bloom on new wood, with their buds forming exclusively in spring on the growth of the current season. Their flowering period generally extends from late summer to early autumn.
Smooth Hydrangeas (Hydrangea arborescens): This variety, including the very popular ‘Annabelle’, also blooms on new wood. The buds appear on the spring growth, and the flowers fully open during the summer.
Oakleaf Hydrangeas (Hydrangea quercifolia): These hydrangeas bloom on last year’s wood. Their cone-shaped flower clusters typically appear from early to mid-summer.
When to Prune Hydrangeas?
For Bigleaf Hydrangeas: Since they bloom on old wood, these should be pruned immediately after flowering, at the end of summer. Pruning too late risks cutting off the buds that will produce the next year’s flowers.
For Panicle Hydrangeas: Pruning is done in late winter or early spring before new growth begins. Because they flower on new wood, this pruning will not affect blooming.
For Smooth Hydrangeas: Similar to panicle hydrangeas, pruning takes place in late winter or early spring without jeopardizing their summer bloom, as they also flower on new wood.
For Oakleaf Hydrangeas: These, which bloom on old wood, are pruned immediately after their flowering period.
How to Prune Hydrangeas?
Remove Dead or Weak Stems: Begin by cutting all dead, damaged, or weak stems at the base. This step improves air circulation within the shrub and encourages vigorous growth.
Prune Faded Flowers: For varieties blooming on old wood, prune just below the spent flowers. It is important not to cut too low because the buds for the next bloom may be located just beneath the faded blooms.
Shape and Size Control: To manage the volume and shape of the hydrangea, selectively prune branches to maintain the desired silhouette. Avoid heavy pruning, especially with varieties that flower on old wood.
Tools and Technique: Use a sharp, clean pruning shear for precise cuts. Make angled cuts at 45 degrees just above a healthy bud or at the junction with a secondary branch.
Depending on the hydrangea variety and its flowering habit, pruning techniques and timing differ significantly. Knowing whether a hydrangea blooms on old or new wood helps you schedule pruning at the right time and apply the correct method. Following these guidelines ensures your hydrangeas maintain robust health and produce abundant blooms for many years to come.
