If the shrub blooms in spring, then prune immediately after bloom period next year. If you prune it now, flower buds will be lost. If it blooms in summer, prune now or in the spring. Endless Summer hydrangea macrophylla blooms on current season growth and old wood, pruning will still result in some flower loss, but pruning can be done now if you can’t wait.

Answered by the UConn Home & Garden Education Center