When to Prune Hydrangeas: Old Wood vs New Wood
When to prune hydrangeas depends on whether the shrub blooms on old wood or new wood. University of Maryland Extension notes many hydrangeas cannot replace flower buds that were removed. Bigleaf plus oakleaf hydrangeas set buds the year before, while smooth plus panicle hydrangeas bloom on current growth.
The short answer
Prune bigleaf plus oakleaf hydrangeas right after flowering because they bloom on old wood. Clemson Cooperative Extension advises finishing before buds form in late summer. University of Minnesota Extension advises pruning bigleaf types before August. Prune smooth plus panicle hydrangeas in late winter or early spring since they bloom on new wood.
Which hydrangeas bloom on old wood?
University of Maryland Extension notes old wood bloomers set buds in summer plus autumn the year before.
| Hydrangea | Blooms on | When to prune |
|---|---|---|
| Bigleaf | Old wood | Right after flowering, before August |
| Oakleaf | Old wood | Right after flowering |
| Smooth | New wood | Late winter or early spring |
| Panicle | New wood | Late winter or early spring |
Source: University of Maryland Extension, Clemson Cooperative Extension plus University of Minnesota Extension.
Which bloom on new wood?
Clemson Cooperative Extension notes panicle plus smooth hydrangeas flower on new wood from the current season. They can be pruned in late winter or early spring before growth begins. Penn State Extension notes both can be cut to the ground then and still bloom.
What happens if you prune at the wrong time?
Penn State Extension notes bigleaf hydrangeas pruned in fall give few or no flowers. Oakleaf pruned at the wrong time also blooms less. University of Maryland Extension notes many hydrangeas cannot replace flower buds once removed.
How to: step by step
- Identify the hydrangea type.
- Check whether it blooms on old or new wood.
- Prune old wood types right after flowering.
- Prune new wood types in late winter or early spring.
- Cut about 1/4 inch above a fat bud.
- Remove no more than a third of the plant.
Troubleshooting
No flowers after pruning: an old wood type was cut at the wrong time. Prune bigleaf plus oakleaf right after bloom.
Floppy smooth hydrangea stems: the plant was cut very low. University of Maryland Extension notes harder cuts give fewer, larger clusters.
Buds lost over winter: cold damaged old wood buds. Reblooming bigleaf types can still flower on new wood.
For related reading see sanitizing pruning shears for cannabis, how to sharpen garden tools plus fall garden cleanup after cannabis harvest. Kind Seed Co also stocks cannabis seeds.
Sources
- Pruning hydrangeas, University of Maryland Extension
- Pruning hydrangeas for best bloom, University of Minnesota Extension
- When to prune which hydrangea species, Penn State Extension
- Pruning hydrangeas, Clemson Cooperative Extension HGIC
FAQ
Can reblooming hydrangeas be pruned anytime?
University of Maryland Extension notes reblooming types bloom on old plus new wood. Early season pruning delays flowering while midseason pruning can shorten the rebloom window, so timing is a personal choice. Clemson Cooperative Extension advises pruning Endless Summer types right after the first flush.
Should dried flower heads be removed?
University of Maryland Extension notes deadheading is not needed for the plant, though it may encourage faster rebloom on repeat flowering types. University of Minnesota Extension notes the dried flower heads give winter interest. Panicle heads can stay until late winter or spring pruning.
Is fall pruning bad?
For bigleaf hydrangeas, yes. Penn State Extension notes bigleaf plants pruned in fall give few or no flowers. University of Maryland Extension advises avoiding pruning close to winter dormancy. University of Minnesota Extension notes panicle hydrangeas can be cut in fall, late winter or spring.
How much can be cut off?
Clemson Cooperative Extension advises removing only a third of the total growth on bigleaf hydrangeas. University of Maryland Extension notes bigleaf plus smooth hydrangeas can be cut to about 12 inches off the ground. University of Minnesota Extension advises cutting just above a fat bud.
Does climbing hydrangea need pruning?
University of Minnesota Extension notes climbing hydrangea needs little to no pruning ever, except for removing dead wood. It is a vigorous vine that clings to walls plus trees. Remove any dead stems after the leaves come out in spring, when it is easy to see which wood did not leaf out.
