In the late winter, early spring, or just above a big bud known as a heading cut, trim back stems. The flower heads of these plants have a conical form. I wait to prune these until late winter or spring because I advise leaving the dried, tan flower heads on the plant to add some winter beauty to your garden. Favorite panicle hydrangeas include:
- H. paniculata ‘Bulk’ PP16, 812, Quick Fire
- (H. paniculata ‘Limelight’)
- Berry White (H. paniculata ‘Renba’ PP28, 509) first editions
When do hydrangeas need to be pruned?
Depending on which group the plant belongs to, the timing and extent of pruning are determined:
Advice on Pruning for Group 1:
- As the days get shorter and the weather gets colder in the late summer and fall, buds for the following year’s blooms start to form.
- Typically, removing dead, diseased, or damaged branches is all that is required to preserve shape, size, and a healthy plant. Otherwise, gentle pruning ought to be practiced.
- In the summer, trimming should begin as soon as flowering ends, but no later than August 1. Pruning should not be done in the fall, winter, or spring because you risk removing fresh buds.
- Tip-pruning the branches in the spring as the leaves begin to appear can promote more numerous, smaller flower heads as opposed to fewer, larger flower heads.
Advice on Pruning for Group 2:
- On the growth of the current year, flower buds form.
- Early in the spring, as the leaves are starting to emerge, prune.
- Just above a node, prune branches back by half to a third.
- After that, prune any fragile or spindly branches.
- Minimal trimming encourages huge, strong bushes with many of tiny flower heads in H. arborescens. Hard pruning between 12 and 18 inches from the ground, or even all the way down, will result in fewer but larger flower heads that may flop if unsupported.
- For H. paniculata, remove the surrounding smaller wood while leaving the larger stems in order to establish a sturdy foundation.
Pruning may be connected to flower head size. Shoots will grow more vigorously and flower heads will be bigger and fewer with more rigorous trimming. Smaller but more numerous flower heads may result from less aggressive or tip pruning.
Consideration of hydrangeas’ mature size is the best piece of advise. Place them in a location where they won’t outgrow and won’t need a lot of pruning to keep them in check. Hydrangeas don’t need to be pruned precisely or often; as long as dead wood is removed, they will remain healthy and continue to develop and bloom.
How deep should hydrangeas be pruned?
Cut these stems just above the soil line. Keep in mind that old wood is where buds for blooms are generated, thus the more old wood you remove, the less blossoms will appear in the spring and summer. Remove up to one-third of the older living stems from the hydrangea each summer, cutting them all the way to the ground. The plant will recover as a result.