The best time to prune hydrangeas depends on the type of hydrangea:

• For most hydrangeas, including mophead, lacecap, and bigleaf hydrangeas (Hydrangea macrophylla) that bloom on old wood, pruning should be done right after flowering ends in summer. Pruning in fall, winter, or early spring risks removing the flower buds for the next season.

• Panicle hydrangeas (Hydrangea paniculata) and smooth hydrangeas bloom on new wood, so they can be pruned in late winter or early spring before new growth begins. Heavy pruning produces fewer but larger blooms; light pruning encourages more blooms.

• Climbing hydrangeas are pruned after flowering in late summer or early fall to avoid cutting off flowers for that year.

• Leaving the dried flower heads on mophead hydrangeas during winter helps protect the buds from frost damage, so it’s advisable to prune in spring to avoid frost damage to new buds.

In summary:

Hydrangea Type| Bloom on| Best Time to Prune
---|---|---
Mophead, Lacecap, Bigleaf| Old wood| Immediately after flowering (summer)
Panicle, Smooth| New wood| Late winter or early spring
Climbing| Old wood| After flowering (late summer)

This timing strategy helps ensure strong growth and good flowering the next season while avoiding frost damage to buds.