Hydrangeas are deciduous flowering shrubs that produce many clusters of colorful, aromatic flowers in the summertime. Approximately 23 species of hydrangea exist, but only five are widely grown in the United States (See Reference 1, par. 1). Among those species are the oakleaf, panicle (Pee Gee), smooth (Hills-of-Snow), climbing, and the most popular, the Hydrangea macrophylla, better known as the florist (bigleaf) hydrangea (See Reference 1). Most of these hydrangea species can benefit from regular pruning, but it is important to know when to prune each species to ensure optimum growth and blooming during the warm growing season.
Identify the hydrangeas. It is important to know what species of hydrangea you have, because some species of hydrangeas need to be pruned in the spring, while others after blooming later in the summer. If unsure of the hydrangea species, check plant identification books from the library or agricultural sites on the Internet to help identify the shrubs.
Prune the overgrown branches of panicle (Pee Gee) and smooth (Hills-of-Snow) hydrangea in late winter or early spring, when leaves are absent on the shrub. Use a sharp pair of garden shears, loppers, or pruners to trim back any dead or undesired growth. Panicle and smooth hydrangea bloom on the current year's growth, and should be pruned before any leaves appear on the shrubs in spring (See Reference 1, pars. 30 and 31).
Remove weather-damaged wood from florist (bigleaf) and oafleaf hydrangeas in early spring, after the danger of frost has passed. These hydrangeas species are prone to damage from cold winter weather, and should be pruned only to remove the dead wood (See Reference 1 & Reference 2, Pruning).
Prune florist (bigleaf) and oakleaf hydrangeas shortly after flowering in the summer. Florist and oakleaf hydrangeas produce blooms on the previous year's growth, so trimming between fall and the following spring could destroy the current year's output of flowers. Cut off old blooms and trim back any deformed or dying branches (See Reference 1 & Reference 2, Pruning).
Climbing hydrangeas do not require regular pruning, but if the vines become overgrown, trim back to desired lengths in summer (See Reference 2, Pruning).