If you are going to raise hydrangeas, it is helpful to know that there are five main types, and of these, the smooth and cluster types are the most reliable for surviving Midwestern winters.
The following is a primer on hydrangeas with information from Ella Maxwell, of Hoyer’s Nursery, Peoria, Illinois, and from Cindy Haynes and Richard Goron, horticulturists at Iowa State University, Ames.
1. Hardy Midwest
Smooth hydrangeas (Hydrangea arborvitae) and cluster hydrangeas (Hydrangea paniculata) are more hardy because their flowers are produced on buds that appear after the plants’ leaves in the spring, so they will bloom no matter how cold the winter is.
• Soft hydrangea is a three- to five-foot-tall shrub that blooms from June to September. The flowers are round and change from apple green to creamy white during the summer. The flowers also appear in the fall, where they fade, turn brown, and last until winter.
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Downy hydrangea can be pruned to the ground in late winter or early spring.
‘Annabelle’ is one of the most popular varieties. The latest is “Invincible Spirit II”.
• Cluster hydrangeas (Hydrangea paniculata) bloom later than smooth hydrangeas, often not beginning until July. But the cone-shaped, creamy white flowers that range from six to 12 inches long are just as persistent. As they age, they often become a mottled pink color. Support is the largest type of shrub, often reaching 10 feet tall.
Regenerative pruning (removing several large stems near ground level) of large, old shrubs can also be done in late winter/early spring.
‘Grandiflora’, ‘Limelight’, ‘Little Lime’, ‘Little Quick Fire’ and ‘Vanilla Strawberry’ are popular cultivars.
2. Three other types that do not prune
The other three types are large-leafed (also called mophead), oak-leafed, and climbing. All three of these flower on old wood (growth established the previous season). This hydrangea should remain undisturbed throughout the fall, winter and spring until it blooms the following summer.
If they are pruned, browsed by deer, or damaged by cold weather, they may fail to flower. Sometimes winter isn’t the problem; Rather, the damage occurs in the spring when several days of warm temperatures are followed by a sudden freeze, killing the buds.
• Mobhead or large-leaved hydrangea (Hydrangea large-leaved) has colorful flowers that are usually sold in flower shops and supermarkets as a cut flower. It is the only type of hydrangea whose flower color depends on soil pH – blue in acidic soil and pink in alkaline soil. Be sure to check the USDA hardiness zone it is classified for; Many varieties are not reliably hardy in Zone 5 which includes most of the Quad Cities area, and will die back in winter.
This is why newer cultivars such as ‘Endless Summer’ have shown such promise because after a mild winter they will flower in early summer on the previous year’s growth as well as in late summer on the current year’s growth. But this did not always happen; Sometimes the old growth flowers die and gardeners are disappointed. They ended up with a lot of foliage and few flowers, until September when the new growth appeared.
Maxwell recommends “BloomStruck” as the most reliable in this series.
• Oakleaf hydrangea (Hydrangea quercifolia) is so named because its leaves are shaped like oak leaves, and its leaves are known for their fall burgundy-red color. He is considered difficult to reach Zone 5 but could use protection.
• Climbing hydrangea (Hydrangea anomalis subsp. petiolaris) can climb to 50 feet. Another interesting feature is its shaggy brown bark that can attract attention in a winter landscape. It is considered hardy to zone 4.
3. Protect plants in winter
One way to protect already set hydrangea buds from the cold is to mulch around the shrub, Maxwell said. Install an 18-inch-high fence of chicken wire around the entire plant and fill it with leaves or straw.
4. For good flowers, stay away from nitrogen
Maxwell advises against giving hydrangeas more nitrogen as found in Miracle-Gro or common fertilizers. A little phosphate will encourage flowering.
5. Buy early, pay attention to the sign
Hoerr sells most hydrangeas when they are in bloom. This is the case with many flowers, because people see the flowers and buy them. But the best time to buy is early, when they are not in bloom. Not only will they do a better job, but you’ll get the best selection.
Also pay attention to the sign. Find out what type you’re getting, what cultural conditions the plant likes (sun/shade/wet/dry) and whether it’s possible to rebloom (grow on old and new growth).
6. In general…
Hydrangeas never like wet feet, and they all like at least four hours of sunlight a day.
(Note: Photos accompanying this story are courtesy of Plant Addicts, a nursery based in Valley, Nebraska, plantaddicts.com)