Master Gardener Nancy Crowe guides the way through the mystique of hydrangeas.There they were in my neighbor’s garden, newly planted hydrangeas with abundant blue blooms. The neighbor, Kay Steinkamp, said they were a Mother’s Day present from husband John, “and they cost about as much as a child,” she quipped.
They are nevertheless delighted with the plants, acquired from a locally owned nursery. The staff took the time to educate the Steinkamps on hydrangea placement and care. So when they brought the plants home, they already knew they needed filtered shade and were a non-pruning species. The two also brought home a special fertilizer to acidify the soil, thereby maintaining the blue hue. They and the hydrangeas are off to a great start.
This, the hydrangea questions we received at the Master Gardener Hotline this spring and a desire to become a better hydrangea steward led me to learn more. What do these beauties need? How do you get them to bloom in blue? What kind of hydrangea is it, anyway?
Luckily, one of the display gardens at the Allen County Extension Office is a hydrangea garden. Two of the Master Gardeners who work on it, Barb Gibson and Joyce Foote, were kind enough to give me a guided tour. They also gave me some good information that, in true Master Gardener fashion, is based on both credible research and hands-on experience.
You’ve got your big-leaf (mophead and lacecap), arborescens (the popular “Annabelle” and family), oakleaf, paniculata and climbing hydrangeas. Hydrangeas come in re-blooming and climbing species as well.
Mopheads and lacecaps —the names basically describe them — bloom in June and July on the previous year’s branches, which in our area puts the flower buds at risk for freezing and dying. The hydrangea garden team has circumvented this by covering them over the winter. You can use burlap or covers available in stores, but forget plastic. “They must be able to breathe,” Foote said. Mopheads and lacecaps should be pruned after flowering is finished.
One of the popular mopheads in the display garden is “Nigra,” with its dark stems and purplish-blue blooms. “This one’s my favorite,” Gibson said.
“Annabelle” is probably the hydrangea you see most often, and for good reason. “It’s as faithful as they get,” Foote said. Severe pruning or nasty winters? No problem. Those poufy white blooms keep coming. This variety should be pruned in late winter or early spring.
There are several beautiful examples of the oakleaf hydrangea (another self-explanatory name, as its large leaves are lobed like those of an oak tree) in the display garden. These are more drought-tolerant than other hydrangeas, which is worth noting; on the day of our tour, we were in what was optimistically called a moderate drought. They’re also bigger, averaging six feet tall. There is currently some controversy over when to prune the oakleaf hydrangea — some sources advise pruning before August 15; others, late winter or early spring. “We are experimenting with ours,” Gibson said. “We will prune a few branches at each of these time frames and note results.”
The paniculata variety is the PeeGee and its family; the nickname stems from the plant’s botanical moniker (paniculata Grandiflora) and not from its suitability for those 13 and younger. The blooms start out white but may develop a pink hue as the blooms age. The “Limelight” paniculata blooms bright chartreuse in summer, and then the blooms turn a rich, deep pink. These need more sun than the other varieties, which seem to prefer dappled shade, and should be pruned in late winter or early spring.
The most common reason hydrangeas fail to bloom, according to the hydrangea display garden team, is winter damage. Others include too much shade, too much nitrogen and poor soil quality.
Obviously, there is much more information than can be included here. Your best source for information about specific hydrangea varieties, bloom times and pruning methods is a reputable nursery that sells them. You can also call the Master Gardener Hotline at (260) 481-6826 or come to one of the plant sales or garden walks at the display gardens. If there is one thing I’ve learned, it’s that there is always more to be learned.
Master Gardener Nancy Crowe's Garden Spot column also appears in interactive format online.