At this time of the year, I get dozens of e-mails asking when and how to prune hydrangeas.
Hydrangea arboresence,"Annabelle," often referred to as the snowball hydrangea, forms its flower buds on new wood in spring. Hydrangea guru Mike Dirr recommends removing their spent flowers by late winter or very early spring before the leaves emerge. Pruning may also be done at this time.
Many gardeners confuse pruning with the removal of spent blossoms. Pruning, the cutting back or removing of branches and stems of a shrub, is done to rejuvenate older shrubs or reduce the size of the plant. Contrary to the urban legend, pruning is not required to make hydrangeas bloom.
At this time of the year, spent blossoms are removed by cutting off the blooms at the very base of the flower cluster. Using this method, flower clusters can be removed at any time of the year on any hydrangea.
When removing the spent blossoms from the colorful pink or blue mophead hydrangeas, Hydrangea macrophylla, or oakleaf hydrangeas, Hydrangea quercifolia, now or in spring, care must be taken not to damage the flower buds that began forming at the tips of their stems in summer. Damage or remove those flower buds and the shrubs will not bloom next summer.
At this time of the year, flower buds on the tips of the stems of oakleaf hydrangeas are light brown and to the untrained eye look to be dried out. When removing the flowers, carefully clip them off at the base of the cluster leaving that brown bud intact. Included in the oakleaf lineup of shrubs are "Snow Queen," "Snow Flake," "Sykes Dwarf" and "lice."
The flower heads of Hydrangea arboresence, "White Dome," are spectacular in winter when covered with frost or snow, so I cut them back in very early spring. Cutting "Annabelle" back hard results in more blooms of smaller size, reducing the chances of drooping when it rains.
Hydrangea paniculata, also called panicled hydrangea, includes the popular cultivars "Limelight" and "Pinky Winky." The flower clusters of these all-stars change colors as they age so gardeners like to leave them intact throughout the growing season.
The tall, upright hydrangeas "Kyushu" and "Tardiva" also belong to the paniculata family. Panicled hydrangeas produce their flowers on new spring growth so gardeners needn't worry about removing next summer's flowers when they cut off spent blooms now through very early spring. And late winter to very early spring pruning to reduce the size of the shrubs will not interrupt their flower production next summer.
