How to Prune Hydrangeas
How to prune hydrangeas correctly by type. Bigleaf and oakleaf right after bloom. Panicle and smooth in late winter. The wrong timing costs a full season of flowers.
This is the most important step. Bigleaf (mophead/lacecap) and oakleaf bloom on old wood: flower buds form in late summer for next year. Panicle (Limelight, Little Lime) and smooth (Annabelle) bloom on new wood: flowers form on current year's growth. Pruning an old-wood type in late winter removes all the flower buds. Check the Types of Hydrangeas guide if you're unsure.
Prune bigleaf and oakleaf hydrangeas in July to August, immediately after flowers fade. Cut spent flower heads back to the first set of large healthy buds below the flower. Remove up to one-third of the oldest, thickest stems at ground level to encourage new growth. Do NOT cut all stems to the ground: you'll remove next year's flower buds.
Prune panicle and smooth hydrangeas in February to March before new growth starts. These bloom on new wood, so pruning stimulates the new shoots that will carry flowers. Cut back to 12 to 18 inches above ground or to a framework of 4 to 6 main stems. You can prune panicle types hard. Smooth types (Annabelle) can be cut to 6 inches for larger flower heads.
Endless Summer, Bloomstruck, and other reblooming bigleaf varieties flower on both old and new wood. Prune spent flowers in summer but leave healthy stems intact. They'll produce a second flush of blooms on new growth. In late winter, remove only dead wood. Don't cut live stems because the old-wood flower buds are still valuable.
Regardless of type, dead stems (brown, hollow, no green under the bark) can be removed at any time. After winter, scratch the bark with your thumbnail: green underneath means alive, brown means dead. In cold climates (zone 5), bigleaf hydrangeas often have significant winter dieback. Remove dead portions down to the first green bud or to the ground.
