As we close in on the time of year when hydrangeas lose their leaves for winter we receive calls about pruning them. “Can I cut them back?” “If so, will they bloom next year?”
All good questions and the answer to that question depends upon the variety of hydrangea that you have. Whether it blooms on last years stems (old wood) or on new growth (new wood).
Panicle Hydrangeas (Hydrangea paniculate)– blooms on new growth so “prune on”. They usually bloom in late summer so don’t prune them then. Examples are: Fire Light, Limelight, Little Lime, Quick Fire, Little Quick Fire
Bigleaf Hydrangeas (Hydrangea macrophylla) – Only prune when the flowers begin to fade. Flower buds begin forming in late summer for the following season, so don’t prune this type of hydrangea after August 1. Examples are: Most are mopheads, some are lacecaps. Cityline series, Let’s Dance series, Endless Summer series.
Smooth Hydrangeas (Hydrangea arborescens) – bloom on new growth so pruning hard in late winter or early spring promotes new growth which will produce more flowers. Examples are: Incrediball series, Invincibelle series, Annabelle.
Oakleaf Hydrangeas (Hydrangea quercifolia) – bloom on the previous season’s growth so prune right after flowering in the fall or in early winter. Don’t take more that 1/3 fo the total growth when pruning. Examples are: Pee Wee, Alice, Ruby Slippers.
This is general pruning information. I suggest verifying the species you have and reading advice that is specific to that species prior to pruning.