Question: I have several types of hydrangeas and I am confused about when to prune them. One year I pruned in the spring and had no blooms. Please advise.
When pruning hydrangeas, it all depends on the variety. Some hydrangeas need to be pruned in the fall or winter; others are pruned in the summer. It can be so confusing! Be assured that pruning at the wrong time will probably not kill your hydrangea. But, it will likely reduce the number of the flowers on your plant or the plant may not produce flowers in the next blooming cycle.
Gardeners can choose from 23 different species of hydrangea. Their growth habits vary from evergreen or deciduous shrubs, to small trees, and vines. They are hardy and resistant to insects and diseases. Hydrangeas grow well in Virginia with regular moisture, soil rich in organic matter, well-drained, and shade in the afternoon.
Know Your Hydrangea Type
There are five species of hydrangeas available in the U.S.: panicle (tree), smooth, bigleaf, mountain, and oakleaf. The panicle and smooth form flowers on new wood; that means wood produced during that year’s growing season. The remaining types of hydrangeas form flowers on old wood; growth from last season. The timing of pruning depends on where the flowers form: old or new wood.
The four types of hydrangeas that grow best in Virginia are: bigleaf (Hydrangea macrophylla), oakleaf (Hydrangea quercifolia), smooth (Hydrangea arborescens) and panicle (Hydrangea paniculata) varieties. It’s likely that you have one or more of these types in your yard.
- Bigleaf (Hydrangea macrophylla) is Virginia’s only native species of hydrangea, known for its mophead or lacecap flower forms. It has large, coarse, medium to dark green leaves, and large blooms. Reaching 6 to 10 feet in height, it grows in partial to full shade but can tolerate full sun if kept moist. Blooms can be white, pink, blue, purple or red, depending on the soil pH. Flower buds develop on the tips of old wood stems.
- Oakleaf (Hydrangea quercifolia) grows to 6 to 8 feet in height and width and thrives in full sun to partial shade. It has large, coarse grey green to dark green foliage resembling oak leaves, and peeling bark. Beautiful fall color ranges from crimson, purple, yellow, gold or bronze. Blooms are conical and range from white to light purple or pink. Flowers develop on old wood.
- Smooth Hydrangea (Hydrangea arborescens) is a smaller variety from 3 to 5 feet tall with a mounded growth habit. It does well in part shade or in full sun (with consistently moist soil). The leaves are large, coarse, rounded and range from medium to dark green in color. Its blooms are either white or pink. Blooms grow on new growth and tolerate heavy pruning.
- Panicle Hydrangea (Hydrangea paniculata) reaches a height of 8 to 15 feet and width of 6 to 12 feet. It prefers full to partial shade. It grows as an upright low- branched small tree or large bush with branches that bend under the weight of the flowers. Its leaves are narrow, serrated and dark green. Blooms are large white conical flowers and the plant is very winter hardy. Flowers grow on new wood.
Guidelines for Pruning
In general, pruning benefits hydrangeas when done correctly because it provides light and air circulation that prevents disease. Don’t prune until the plant is 5 or 6 years old. Here are some pruning tips for the common types of Virginia hydrangeas:
Smooth and panicle hydrangea (blooms on new wood):
- Prune in fall or winter, when plants are dormant (before new growth begins).
- Thin out excessive growth or prune the whole plant back to the ground.
- Heavy early pruning will produce smaller plants with larger blooms, not pruning will produce larger plants with many small blooms.
Oakleaf hydrangea (blooms on old wood):
- Prune in summer, immediately after flowering.
- Prune the dead wood anytime, cutting back just above the buds on stems and/or remove the largest canes to the ground.
- Prune sparingly to enjoy the amber peeling bark and lovely fall color.
Bigleaf hydrangea (blooms on old wood):
- Prune in summer, immediately after flowering.
- Remove up to 1/3 of the plant growth.
- Prune the dead wood anytime, cutting back just above the buds on stems and/or remove the largest canes to the ground.
- Severe pruning in the spring will greatly reduce blooming potential.
- For ever-blooming varieties of bigleaf, which bloom on both old and new wood, prune after the first flowering.
NOTE: To make sure to prune only dead wood: scrape a small amount of bark off the stem with a pocketknife. If it’s green, don’t prune it.
Although improper pruning is likely the source of the lack of blooms on your plants, be sure to look at these troubleshooting tips to rule out other causes.
Now you have the knowledge to understand why your hydrangeas didn’t bloom! It seems that you have hydrangeas that bloom on old wood (like the bigleaf or oakleaf varieties). Pruning in the spring after the flower buds have developed will greatly reduce or eliminate that year’s blooms.
Interested in learning more about these and other hydrangeas? Explore their different characteristics by consulting the North Carolina Extension Gardener Plant Toolbox, learn how to select the right hydrangea for your setting and preferences, and how to plant and care for them. If you have oakleaf or mountain hydrangeas, you can even change the color of the blossoms!
References
“Hydrangeas,” Kerry Smith et al., Alabama Cooperative Extension System, Home Lawn & Garden, Flowers, 10 Dec. 2018.
“Hydrangea Selection, Pruning and Care,” Mike Andruczyk, Horticulture Extension Agent, Chesapeake, Virginia Cooperative Extension.
“Pruning Hydrangea,” Andrew Jeffers, Horticulture & Natural Resource Agent, Clemson, Spartanburg Cooperative Extension, Clemson University, 5 Mar. 2020.
“Guide to Pruning Hydrangeas,” Raymond Bosmans, Professor Emeritus, University of Maryland Extension, 24 May 2021.
“Selecting Hydrangeas for the Home Landscape,” Eric Barrett, Assistant Professor, Extension Educator, Agriculture & Natural Resources, Mahoning County, Publication HYG-1263, 20 Jul. 2018.
“Solving the Hydrangea Puzzle,” Emma Erler, Landscape & Greenhouse Field Specialist, Instructor Field Specialist, University of New Hampshire Cooperative Extension, 16 Apr. 2018.
“When Should I Prune My Hydrangea?” Norm Phillips, UC Master Gardener, Tulare & Kings Counties, University of California Cooperative Extension, 29 Aug. 2013.
“Why You Have Few Hydrangea Blooms,” Elaine Homstad, Fairfax Master Gardener, Fairfax Gardening, Fairfax County Master Gardeners, 2016.
