Is your prized hydrangea not blooming yet? Doris Taylor, Plant Clinic manager at The Morton Arboretum, is on the case. “We often get that question this time of year. It takes some sleuthing,” she said.
A few common hydrangea problems:
Wrong pruning time. “Some popular hydrangeas, including oak-leaf hydrangea (Hydrangea quercifolia), made their flower buds during last year’s growing season. If you pruned them within the past 10 months, you’ve likely cut off this year’s flowers,” said Taylor. Prune Hydrangea quercifolia, H. serrata, and most H. macrophylla cultivars immediately after blooming.
Overfertilizing. “Many people reach for the fertilizer when they see leaf spots. But fertilizers, especially high nitrogen ones, encourage leaf growth at the expense of flower production,” said Taylor. Skip the fertilizer and apply organic mulch.
Too little or too much sun. “Hydrangeas need four to six hours of sun a day, preferably morning sun,” said Taylor. If a dense shade tree is filling in overhead, you may see sparse flowering. At the other extreme, too much direct sun stresses the plant. Give a plant in full sun plenty of water and mulch the roots — or move it to a part-shade location this fall.
Wrong hardiness zone. “If your hydrangea isn’t coming back well each winter, check its USDA Plant Hardiness Zone,” Taylor said. The plant should be hardy to our Zone 5 area.
Acclimating. “Give a new hydrangea a season or two to set roots. Transplanting is stressful,” said Taylor.
For free advice about selecting and caring for hydrangeas, contact The Morton Arboretum Plant Clinic at
, call 630-719-2424, or visit mortonarb.org/tree-plant-advice. Laurie Casey is a staff writer at The Morton Arboretum in Lisle.
