Taking the mystery out of pruning hydrangeas

Hydrangeas have long been popular in the landscape. They have an allure. It’s as if they speak to us, saying, “Come plant me; enjoy me in the garden.” Resisting the temptation is hard.

Once planted, confusion sets in about proper care, especially pruning. How, when and where are common questions received at Johnson County K-State Research and Extension. To unravel the confusion surrounding pruning this plant, determining the type of hydrangea is key.

▪ Hydrangea macrophylla: These big leaf or mophead hydrangeas are the most popular. They have big rounded pink or blue blooms. Popular varieties include the Endless Summer Series, Cityline Series and Let’s Dance Series.

Mopheads bloom best on old growth, as the buds are set the previous fall, overwinter and open the following spring. Many varieties set a secondary flower bud, which flowers in late summer. Early spring pruning should be limited to only dead wood. Cutting into healthy buds results in the removal of potential flowers. Controlling plant size and shape are accomplished after flowering. This allows time for the fall bloom and next year’s buds to develop.

▪ Hydrangea arborescens: This group is best known by the popular variety, Annabelle, or the smooth leaf hydrangea. Other varieties are Invincibelle Spirit and Incrediball. Unlike the big leaf hydrangeas, this group blooms on new spring growth.

Smooth leaf hydrangeas are the easiest to grow. Pruning is simple. Cut the old stems back to just above the lowest plump bud above the ground every spring. Harsh pruning brings big rewards. Each trimmed stem leads to a sturdy stem capped off with a big rounded flower in either white or pink, depending on the variety.

▪ Hydrangea paniculata: Panicle hydrangeas flower in white with some tinges of pink. The flowers usually are rounded with an elongated point. Popular varieties are Limelight, Quickfire, Tardiva, Pinky Winky and Vanilla Strawberry.

This easier group blooms on new growth that is produced in the spring and early summer. Flowering starts in July and can last through August. Pruning is done in the early spring when breaking bud. Panicle types can get large. More pruning leads to bigger flower heads. Cut back the growth to a bud about 2 feet from the ground. Remove pencil-size wood, as it takes a sturdy branch to hold a big flower.

▪ Hydrangea quercifolia: Oakleaf hydrangeas are a classic. These plants have deeply lobed leaves and long showy spring flowers. Varieties on the market include Alice, Snow Queen, Sikes Dwarf, Pee Wee, and Ruby Slippers.

These spring bloomers produce their flowers on old growth, like the macrophylla group. This means little or no pruning happens in the spring. Remove dead twigs, enjoy the flowers and then do the bulk of pruning after the show wanes.

The best advice is to limit pruning altogether. Oakleaf’s have beautiful cinnamon-colored bark that peels and is quite ornamental. Heavy pruning reduces winter interest. Be warned, some of these varieties get big — over 8 feet.

This story was originally published March 17, 2017 at 3:11 PM with the headline "Taking the mystery out of pruning hydrangeas."