Say ‘hi’ to popular, confusing hydrangea

Posted on Aug 01 2016 in Backyard

By B. Rosie Lerner


Photo by Rosie Lerner/Purdue Extension

Hydrangeas are popular, but understandably confusing! There are about 25 species, though only five are primarily grown in the U.S. There are literally thousands of cultivars. Some species are classified as either mophead (all large, sterile florets) or lacecap (fertile, center florets surrounded by larger, sterile florets), depending on cultivar. The showiest part of the flower cluster is actually the bracts rather than petals. The bracts persist long after the petals drop and are often cut for dried floral arrangements.
• Smooth hydrangea (H. arborescens) is a native species and features large clusters of pale, greenish blooms, changing to white and then drying to papery brown; blooms on new wood, or current year’s growth. So, it’s often best to prune back to a few inches in late winter for sturdier stems.
• Oakleaf hydrangea (H. quercifolia) is a dramatic native species with foliage shaped like an oak leaf. It offers outstanding fall color and a cinnamon-brown, peeling bark visible in winter. Its showy blooms come in late spring and early summer. It is generally a large, coarse shrub, though some compact cultivars are available. Prune, if needed, after blooming.
• Panicle hydrangea (H. paniculata) is a large shrub, native to Asia, most with cone-shaped clusters of white flowers; blooms mid-summer on new wood, can prune end of winter.
• Bigleaf hydrangea (H. macrophylla), the most popular species, is native to Japan. But most selections bloom only on old wood (previous year’s growth), and foliage usually is killed to the ground in Zone 5, frequently in Zone 6. A few cultivars will also bloom on new wood but are showiest on old wood. Flowers are blue in acidic soil, pink in alkaline soil. If your hydrangea never blooms but produces lovely foliage every year, it is likely this species and flower buds were winter killed.
• Climbing hydrangea (H. anomala petiolaris) is also native to Asia. This striking clinging vine (root-like fastholds) with fragrant, lacecap flowers on current season’s growth and has interesting cinnamon, peeling bark. It needs sturdy support. Hydrangea-vine is a separate but related genus (Schizophragma spp.)

Rosie Lerner is the Purdue Extension consumer horticulturist and a consumer of Tipmont REMC. Have a question about gardening? Use the form to send it to us. Or, questions about gardening issues may be sent to: “Ask Rosie,” Electric Consumer, P.O. Box 24517, Indianapolis, IN 46224, or