How to Prune a Hydrangea Bush

Hydrangea bushes (Hydrangea spp.) grow in U.S. Department of Agriculture plant hardiness zones 4 through 9 and can be divided into two categories based on their blooming habits. Hydrangeas that bloom on old wood include mophead or French hydrangeas (H. macrophylla), mountain hydrangea (H. serrata) and oakleaf hydrangeas (H. quercifolia). Those that bloom on new wood include panicle hydrangeas (H. paniculata) and smooth hydrangeas (H. arborescens). Both types are pruned in the same way, but old-wood-blooming hydrangeas are pruned immediately after flowering, and new-wood hydrangeas are pruned in late winter before they flower.


Clean and disinfect bypass pruners in a solution of 1 part chlorine bleach and 9 parts water. Keep the solution on hand so you can disinfect again immediately after each cut into diseased wood.


Cut expired flowers off the stem just below the flower head and just above a leaf set immediately after the flowering period ends. Flowers that bloom on old wood bloom from early through mid-summer and should be pruned no later than August 1; flowers that bloom on new wood bloom from mid-summer into fall. If desired, you can leave expired blossoms on new-wood-blooming panicle and smooth hydrangeas over winter to add a bit of color to your garden until you prune in late winter.


Remove all dead, broken canes from the bush as you notice them, regardless of when the bush blooms. Dead wood will not produce flower buds for the next year, anyway, so you don't sacrifice next year's flowers if you prune outside the schedule for living wood.


Cut diseased canes back to the ground as they occur to prevent the disease from spreading throughout the bush. Look for discoloration or spotting on the leaves and stems to indicate disease. If you are unsure, it is better to remove the cane to make room for a new cane than to risk disease to the entire plant. Disinfect pruners immediately with the bleach solution before continuing to prune the hydrangea.


Cut any stray or straggly canes back to the ground to help shape the plant. Cut out any branches that are much longer than the surrounding branches to control the height.


Eliminate weak or spindly stems, cutting them back to the ground to make room for new strong canes.


Remove any canes that rub other canes in the bush to keep the inside of the plant open. When selecting between two rubbing canes, choose young, healthy and outward-growing canes over old, weak and inward-growing canes.


Cut out the oldest canes from the bush, removing no more than one third of the total canes, to rejuvenate the bush. Selective thinning of the oldest wood encourages the plant to produce new canes. Remove another third of the oldest branches in the following year; remove the final third in the third year to completely rejuvenate the bush. This pruning practice might not be necessary with younger bushes, but plants that seem crowded or that have less productive flowering can benefit from renewal pruning.


Cut all canes back to rejuvenate older panicle and smooth hydrangeas, which bloom on new wood. This pruning method is optional but often leads to larger flowers on the ends of the new canes; smooth hydrangeas, in particular, are often hard-pruned in this way to produce large flowers each year. Young canes with large flowers might flop over under the weight of the flower, but you can cut the stems to 18 to 24 inches above ground, leaving a framework to help support the new canes. This step is not recommended for bushes that bloom on old wood unless the entire plant could benefit from rejuvenation, but those bushes will not produce flowers until the following years.