Colorful hydrangeas add dramatic appeal to the landscape
There may be no other plant that can change the look of a landscape like hydrangea. With their large, textured leaves and large, showy flowers, hydrangeas can transform a cheerful garden space into a colorful, visually interesting and almost dreamlike landscape with their oversized blooms that can bloom from the May to fall months. Hydrangea’s blooms remaining on the plant during the winter provide a visually attractive addition to a barren winter landscape.
The popularity of hydrangeas among home gardeners has increased over the past several years, likely due to the proliferation of new varieties of hydrangea available in varying plant sizes, growth characteristics, flower types and colors, and leaf shapes. There are six species of hydrangea commonly grown in Ohio including: smooth hydrangea, tree hydrangea; Oak leaf hydrangea, Hydrangea hydrangea; Hydrangea bigleaf, Hydrangea large; Mountain hydrangea, Hydrangea serrate; Climbing hydrangea, Hydrangea hydrangea; Hydrangea panicula, Hydrangea panicula. Gardeners will find many different cultivars of each of these types of hydrangea.
Choose a location
Hydrangeas are woodland plants that need some shade to thrive, even if they are classified as full-sun plants. In the garden, most varieties planted in full sun will have flowers that fade and turn brown more quickly and the leaves wilt during the hottest part of the day. Increased watering can help reduce the effects of full sun, but these locations are not ideal for most hydrangeas.
Planting hydrangeas in heavy shade will result in reduced foliage growth and smaller flowers in some varieties. The ideal location for hydrangeas is one that receives morning sun with shade in the afternoon or one that receives filtered sunlight throughout the day.
Hydrangeas prefer well-drained loamy soil, which contains more sand and silt than clay. Soil with heavy clay and poor drainage should be amended with compost and other organic matter to make it suitable for hydrangeas. Hydrangeas should never be planted in locations where water is slow to drain after rain. Although they need adequate soil moisture, hydrangeas do not like wet roots.
Soil moisture is critical
The name hydrangea comes from the Greek word hedor, meaning water, which explains the plant’s preference for moisture. The specific water needs of hydrangeas can vary by species, with large-leaf hydrangeas requiring the most soil moisture and oak-leaf hydrangeas requiring the least. All hydrangeas require adequate soil moisture, especially during periods of dry weather, so gardeners should always cover the soil around hydrangeas with mulch to maintain soil moisture. During periods of drought or high temperatures, hydrangeas will benefit from the use of drip irrigation or soaker hoses to maintain adequate soil moisture.
When to prune to maximize flowering
Some hydrangeas fail to bloom every year due to cold weather and improper pruning habits. Some hydrangea species form flower buds on “old wood” in August of the season before they bloom. If these plants are pruned in the fall, there will be few, if any, flowers the following season. And if you grow hydrangeas, I think you’re interested in their flowers! Therefore, these types of hydrangea should be pruned in late spring after the buds have matured and are visible to the gardener.
Other types of hydrangea put flower buds on “new wood” during the year they bloom. These plants can be pruned in fall or early spring. Some large-leaved and mountain hydrangeas thrive on new and old wood, so when purchasing hydrangeas, gardeners should research the cultivar’s characteristics, understand when buds are formed and prune accordingly in order to achieve maximum blooms.
To learn more about growing hydrangeas, visit go.osu.edu/hydrangeas. This site includes a helpful chart outlining the characteristics and requirements of different hydrangea species and cultivars suitable for Ohio, as well as a log that gardeners can use to document which varieties perform best in their garden.
Mike Hogan is an associate professor at Ohio State University and an extension educator at Ohio State University Extension.