Hydrangeas have beautiful colors when they bloom, so knowing how to prune is a key factor to keep them blooming. Pruning will help maintain the size of the shrub, remove dead growth, and focus its energy on new foliage, and the best tool to use is a bypass pruner — or a specialty version for thicker branches.
Blooming on new wood means the flower buds formed on the stems have grown this year, so you don’t want to prune them in early summer, as you could snip off any potential flower buds for the current season. The best time to prune arborescens and paniculata hydrangeas would be in the fall, winter, or early spring.
Some hydrangeas bloom on old wood, meaning next season’s flower buds start to grow the year before on last year’s stems, and depending on the variety of the hydrangea, the leaves can either bloom to be large, round mopheads or flatter, lace-caps. The quercifolia, serrata, and macrophylla varieties should be pruned in July as the blooms start to fade.
While most hydrangeas are shrubs, the hydrangea petiolaris is a vine that usually takes up to five years before you see any blossoms, so you want to wait two to three years until the summer after blooming to prune them. Another exception to pruning is the hydrangea macrophylla, which blooms twice in one season and will grow green buds on its old stems in the spring, which will eventually blossom.