Understanding how to perform the pruning of any given plant with regards to their individual needs is a key to success in your garden or commercial production. There are many reasons to prune shrubs. For the hydrangea plant, the purpose and importance of pruning is to:
Different degrees of pruning will give various responses from the plant. It is critical to choose the proper timing as well as age of the stems to be cut. Early training and pruning helps ensure that your hydrangea plant will have a firm foundation and express desirable characteristics as mature plants.
In general all types of hydrangeas respond well to pruning.
HYDRANGEA Macrophylla (Big leaf hydrangea)
Hydrangea macrophylla bears its flowers terminally (at the end of the stems) in the summer time. There are many cultivars. The most common are mop-head hydrangea and lacecaps hydrangeas. Flowers are born on the previous season’s wood. In warmer climates it is best to prune after flowering in the fall. In colder climates it is best to leave the old flower heads on over the winter and prune in midspring.
Cut out weak stems completely to the ground. Shorten the flowered stems to the last pair of healthy, fat buds. These will produce flower shoots. Do not prune shoots that have not flowered as this may prevent blooming later in the summer. If your plant has been neglected and overgrown, you can cut it totally back. Prune each stem to the last pair of strong buds. Such pruning will prevent flowering in the summer but will help rejuvenate your plant into a stronger, healthier producer the following year.
HYDRANGEA Paniculata (Peegee hydrangea)
This shrub has an upright growth habit and bears large panicles of flowers in late summer. In opposition to the Hydrangea macrophylla, Peegee hydrangeas will flower on the current season’s growth. It is best to prune early in the spring prior to active growth.
It is best as young plants to promote a strong woody framework. Cutting all weak stems and leaving the strong can accomplish this. Stems should measure about 10-24 inches (25-60cm). As mature plants, prune out all lifeless stubs and prune back all the shoots to their lowest pair of healthy buds above woody framework
HYDRANGEA Anomala (Climbing hydrangea)
Their flowers are borne in summer on the previous years lateral (side) shoots. Prune in the fall after blooming.
As young plants, most shoots should be secured to some sort of support structure and trained where you want them to go. Pruning of established plants should be kept to a minimum. In order to promote flowering, cut back all shoots that flowered to a healthy bud. It is good to shorten long stems and outward growing laterals to allow more sunlight into canopy.