How much do you trim back a hydrangea and still get flowers in summer?
How much to cut back your hydrangea depends on the variety of
hydrangea you have, and where you live. In northern climates
"Annabelle" and "pee gee" hydrangeas can be cut back to eight
inches, and still produce a three foot-high shrub with flowers
during the summer. "Mophead", "Lacecap" and "oakleaf" hydrangeas
set their blooms in late August, September or October, so you have
to prune them in early August to be sure you aren't cutting off
next year's blooms. Prune out up to a third of the stems of an
older plant to encourage new growth. Prune those stems to the
ground. Otherwise it usually isn't necessary to prune them at all.
Just cut off the spent flowers (deadhead) down to the next stem or
mature leaf.