Q. How and when do I prune my hydrangea bush?
The answer to this question depends on what kind of hydrangea you have.
There are several kinds of hydrangeas:
- Mophead (H. macrophylla) and lacecap hydrangeas (H. macrophylla normalis): These are usually blue, pink or purple (not white). Their leaves are thick, crisp, shiny, and coarsely toothed. Lacecaps differ from mopheads in having smaller florets in the center of the bloom (these are fertile flowers).
- ‘Annabelle’ and related H. arborescens species: These have very large flowers made up of a large number of small individual flowers (often called snow balls). The blooms open green and turn white in 2-3 weeks. Their leaves are thinner and floppier than mopheads and lacecaps.
- Paniculata or peegee (H. paniculata): There a great number of varieties of paniculate hydrangeas, varying in size from small shrubs to small trees. Bloom shapes vary but are often cone-shaped. Their leaves are smaller, thinner and rougher than other hydrangeas, and characteristically 3 leaves grow from a node in a whorl.
- Tree of heaven (H. serrata): This species is sometimes confused with mophead hydrangea, but it has smaller, narrow, pointed leaves.
- Oakleaf hydrangeas (H. quercifolia): These can be distinguished by their leaves that resemble those of red oaks. The blooms open white and turn pink as they age.
- Climbing hydrangeas (H. anomala ssp. petiolaris): This is the only hydrangea that grows like a vine.
Once you have identified your hydrangea, you are ready to consider pruning it. All hydrangeas should have dead or sickly wood removed to keep them healthy. However, a general rule is that pruning should be avoided except when absolutely necessary
Mophead and lacecap hydrangeas – these types bloom on old wood (stems that have been on the bush since the summer before). They should be pruned in the summer when the flowers have started to fade but before August. Pruning after this time removes the buds that will produce flowers next spring. A bush can be trimmed by cutting back stems close to a node. If the plant is overgrown, prune back about 1/3 of the older stems almost to the ground each summer. Note that there is a small group of mop-heads that will bloom no matter when they are pruned; these are called “everbloomers” (‘Endless Summer’ is a common variety).
Paniculata (such as peegee and ‘Limelight’) and ‘Annabelle’ hydrangeas – these types bloom on new wood and can be pruned at any time except in the spring or summer (for peegee) after the new growth has started. Late winter is best. Paniculata hydrangeas can also be pruned into tree forms. If you aiming to do this then the main trunk and the top branches should not be removed.
Tree of heaven also blooms on new wood and should be pruned as for paniculata types.
Oakleaf hydrangeas rarely need pruning. If they need to be pruned for shape or size, follow the rules for mophead hydrangeas.
Climbing hydrangeas also need little pruning. They can be lightly pruned for shape in late summer. If more drastic pruning is needed, early spring is best.
For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service