How should I prune different hydrangea varieties?
Written by
Michael Sullivan
Reviewed by
Prof. Martin Thorne, Ph.D.Correct pruning procedures will separate the difference between barely blooming hydrangeas and those that bloom outstandingly. Each variety requires a different procedure, determined by the type of wood in which it blooms. Knowing whether your hydrangea blooms on old or new wood is crucial for identifying the optimal time frame for pruning. Pruning at the wrong time or during the wrong stage of growth can result in the protection or removal of flower buds; the choice is yours.
Old Wood Bloomers
- Bigleaf and oakleaf hydrangeas form buds on previous season's growth
- Prune immediately after summer flowers fade to preserve next year's buds
- Remove only spent blooms and dead/damaged wood using sharp bypass pruners
New Wood Bloomers
- Panicle and smooth hydrangeas develop buds on current season's growth
- Cut back stems by one-third in late winter before spring growth begins
- Shape plants by removing crossing branches to improve air circulation
Reblooming Varieties
- Deadhead first blooms in summer to encourage secondary flowering
- Use the deadheading technique throughout the blooming season
- Avoid heavy pruning that reduces the plant's energy for reblooming
Pruning Tools & Safety
- Sterilize tools with 70% alcohol between plants to prevent disease spread
- Make clean 45-degree angle cuts just above leaf nodes
- Dispose of infected plant material away from your garden
Flower bud conservation is largely dependent on specifics regarding when plants bloom. Old wood bloomers will start setting flower buds in late summer, which will bloom the following spring. If they are pruned after August, those developing buds will be cut off, resulting in the loss of bloom. New wood bloomers set their buds in spring, so pruning them in winter can actually encourage their growth. For example, I prune my panicle hydrangeas in February before new leaves emerge.
Consequences of improper pruning can include total bloom loss, especially in old wood varieties. Over-pruning can cause stress to the plant, resulting in smaller or fewer blooms. Under-pruning, on the other hand, creates dense growth which can lead to disease pressure. My neighbor lost all blooms on her lacecap hydrangea after pruning it in the fall. Strictly adhere to variety-specific schedules.
Throughout summer, reblooming hydrangeas require some extra deadheading techniques. When deadheading, remove clusters of spent flowers just below the bloom head. When cutting back excess flowers, cut above the first pair of solid healthy leaves to activate and encourage secondary buds. Continue deadheading every 7-10 days during the peak bloom period to initiate a continuous supply of flowers.
The tools you use should always have sharp, sterilized blades to make healthy cuts. Bypass pruners will produce a clean cut without crushing the stem. I disinfect my tools after each plant with coronavirus wipes or rubbing alcohol*. I also replaced my pruner blades every year or two, or whenever they dull. Keeping tools sharp and clean will help prevent the possible transmission of diseases from one shrub to another.
Read the full article: How to Care for Hydrangea: Complete Growing Guide
