Belcarra Garden Club
BC, Canada

Hydrangeas and Pruning Tips

 

Did you know that our lovely hydrangeas, native to the misty forests of Asia and parts of the Americas, have a rich history? A fossil species was found in Alaska that dates back 23 million years, and by the 8th century, these “Rain Flowers” (Ajisai) were cultivated in Japan. One legend says the flower’s colors reflect the emotions of the gods, and another tells of a young woman, abandoned by her lover, whose tears grew into flowers. In Chinese as well as some Native American tribal medicine, the roots of certain species have been used for treating kidney, urinary, and skin issues. BTW, the showy “petals” are modified leaves. The fertile “real flowers” are the very tiny centers.

Seeing those green “buds” is exciting, but before you grab your bypass pruners, you must identify which hydrangeas you have. In our climate, pruning the wrong bush right now means you’ll be looking at nothing but green leaves all summer! Hydrangeas fall into two categories based on when they set their flower buds. One group blooms on old wood, and the other blooms on fresh stems.

1. “Hands Off” Group (Blooms on old wood): The Bigleaf Hydrangea, including classic Mopheads and Lacecaps (Hydrangea macrophylla-many varieties available!), Mountain Hydrangea (Hydrangea serrata -Tuff Stuff Lacecap), and Oakleaf (Hydrangea quercifolia -Gatsby) should only be deadheaded by cutting just above the first pair of healthy, fat green buds. Brittle grey stalks can be cut to the ground. These are pruned only right after blooming in August, so next year’s flower buds can develop
   
   
2. “Go for It” Group (Blooms on new wood): These bloom on the fresh stems that grow in the spring. Panicle Hydrangea (Hydrangea paniculata - Bobo, Limelight, Vanilla Strawberry) can be cut back by about one-third to one-half their height to encourage stronger stems. Smooth Hydrangea (Hydrangea aborescens -Incrediball) can be cut down to about 12 to 18 inches from the ground to keep the shrub tidy and produce huge blooms. (Note: Hydrangea aborescens “Invincible Lace” has Lacecap flowers!)

Note: Our mild winter might have encouraged early growth. 
Keep some frost cloth handy in case of any late frosts that could turn those green buds black overnight. “Old Wood” varieties should also be protected from frost.

Note: Make sure your pruning shears are clean and sharp to prevent disease. 
Always make your cuts at a 45-degree angle about ¼ inch above a node (where the buds are).  This directs water away from the bud and prevents rot in our rainy climate.

 

Mopheads and Lacecaps have large, heart-shaped leaves, often glossy with serrated edges. The older, woody stems don’t die back in the winter. Mopheads have big round balls completely covered in sterile florets. Lacecaps have a ring of showy sterile florets around a center of fertile, often small, florets. For both types, prune lightly and only dead wood.

Oakleaf Hydrangea have leaves like giant oak leaves which are bronze in the fall. The flowers are in a long-branched cluster which turns pinkish purple. They bloom in late spring or early summer. Only prune to shape. (Prune in late winter or early spring.) They prefer a warm, sheltered location.

Panicle Hydrangea have pointy, cone-shaped flower clusters. The leaves are usually slightly narrower and may have a more pointed tip. The stems are sturdy with more of a shrub or small tree structure. Blossoms often start white and then turn pink or reddish. Cut back by 1/3.

Smooth Hydrangea have round, pom-pom white or sometimes pink flowers.  The leaves may be duller green, somewhat thinner. Stems are less woody, so they have a generally floppier appearance.  Cut right down to 12” above the ground.

 

 

So the next time you pause to admire a hydrangea in full bloom, take a moment to appreciate not just what you see—but the centuries of legend, science, and devotion that brought that remarkable flower to your garden.  Our gardens are so much more than just a collection of plants!