Do next years blossoms come on new or old growth?

If you asking about old and new growth on Endless Summer^® hydrangeas, they bloom on both old and new growth which is why we don’t recommend doing a hard prune ever. The first set of blooms for next year are set on the plant this fall, so you don’t want to cut back at all this year. And then the hydrangea will rebloom, producing additional flower buds on new growth, giving another set of flowers later in the season. This differs from panicle hydrangeas, which only bloom on new – or the current season’s – growth.