Correct pruning of hydrangeas depends on the type of hydrangea: Bigleaf or mophead hydrangeas need pruning in summer after their flowers have faded, whereas oakleaf, sevenbark, peegee and Tea of Heaven hydrangeas need pruning in late winter or early spring. Climbing hydrangeas seldom need pruning except to control excess growth.
Bigleaf hydrangeas include varieties that change blossom color according to soil acidity or alkalinity and lacecap hydrangeas, which have flowers that look like a circle of unopened buds surrounded by petals. These hydrangeas start developing buds in the late summer or early fall, and pruning too late in the year typically destroys next year's bloom. The plants benefit from selective pruning that removes dead or weak stems. Gardeners should leave healthy old stems in place as the plants flower on these while new stems mature. These plants are vulnerable to cold injury in the winter and benefit from protection with burlap wraps on their branches.
Oakleaf, sevenbark, peegee and Tea of Heaven hydrangeas bloom on new wood. Gardeners should remove dead stems while the plant is dormant and cut back damaged stems to below the point of injury. Peegee hydrangeas tolerate gentle pruning to shape the plants and encourage new growth.