Q. My hydrangea, called "Annabelle," has many huge white blooms but they flop over and look messy, and many stems have no flowers. How can I prevent the flop and shape up the plant?
A. Hydrangea "Annabelle" is an arborescens-type hydrangea and has a growth habit that differs from the blue-flowered, mophead-type hydrangeas. You may notice that the stems of "Annabelle" are slimmer than mopheads and that the leaves are smaller and softer. But the slim stems must support the large, white blooms that can reach football size. No wonder the blooms tend to be beaten down and cause the stems to break, especially in very rainy summers.
The plant tends to have an upright shape and, while old stems have few flowers, in good garden soil with a reasonable amount of sunlight, arborescens-type hydrangeas will bloom reliably every year. Unlike mopheads, late frosts usually will not inhibit blooms, since the plant blooms on the current year's growth. This will give you a clue to how to manage your Annabelles. You can remove spent or dried blooms whenever you want to over the summer, or you can thin out the blooms to keep the plant neat.
You can add supports, bamboo stakes or metal posts to hold up the heavy blooms. The important job is to cut the plant back before growth begins in the spring or after the plant loses its leaves in the fall. You can cut back the stems from a foot tall to two or three feet, depending on how weak the stems have been.
You should cut them back every year so the plant will grow new strong stems, which will produce larger flowers and fewer weak side shoots that droop. You cannot do this to mophead hydrangeas because you will prevent all flowers, but Annabelles love it.
Fertilize with some good garden compost, lots of sunlight, even moisture, and your Annabelle should be shapely and blooming.
Contact Pat Lea at firstname.lastname@example.org.