Hydrangeas are prized for their clusters of flowers, which are produced at various times throughout summer depending on the variety. Once the blooms begin to fade, the pruning practice known as "deadheading" may help the plant remain attractive for the rest of the growing season. Whether you should deadhead or not depends on both the variety of the hydrangea and your personal preference.
Purpose of deadheading
Deadheading improves the appearance of the bushes as wilting flowers begin to look bedraggled and worn. Some varieties of hydrangea, such as the bigleaf varieties, are more likely to bloom a second time later in the season if the old flowers are removed. Seeds form inside the flower. Deadheading prevents the seeds from forming, which encourages these hydrangeas to attempt seed formation a second time by producing more flowers. Flower removal also keeps the dead plant material from eventually ending up in the garden bed, where it may provide nesting material for insect pests and disease organisms.
Pinching requires no special tools and can be done when you have a spare moment. Break the old hydrangea flower off behind the flower head. At the base of each wilted flower is a swollen area where it joins to the stem -- this is where the seeds are formed. When deadheading, remove the swollen area along with the spent flowers. While pinching is suitable as the first flowers begins to fade, later in the blooming season pruning shears speed up the chore. Trim away all the spent flowers with the shears and dispose of the removed blossoms.
Hydrangeas that benefit from deadheading
Not all hydrangea require deadheading. Oakleaf and climbing hydrangea flowers remain attractive for several weeks after they have faded and dried on the plant. Only deadhead these plants if desired or if the dried flowers become battered and bedraggled. Bigleaf, garden and French hydrangea bloom in early summer but a second flush of late summer flowers is possible with prompt deadheading after the first flush of bloom. Other hydrangea varieties do not reflower, even if deadheaded, so any deadheading is done only to clean up and improve the appearance of the bush.
Other pruning methods
Hydrangea bushes have other pruning needs beyond deadheading, depending on the variety. Peegee and smooth varieties do not require deadheading, but benefit from a severe pruning in late winter, as they bloom primarily on new wood. Cut the entire hydrangea back to within 15 to 30 cm (6 to 12 inches) of the ground. Bigleaf and garden varieties bloom on old wood, so only remove dead stems and up to a third of the still productive stems if necessary to control the size and density of the hydrangea. Prune these in early spring to remove dead wood, or wait until just after the first summer flowering period ends. All other hydrangea only need minimal pruning to remove dead wood and to shape the bushes.