||Dr. Gouin's Bay Gardener
Four different species of hydrangeas grow in the Bay area. The most common species are those that produce red, pink or blue flowers commonly known as Hydrangea macrophylla or house hydrangea.
House hydrangeas are pruned in early April by first removing the canes, as close to the ground as possible, that produced flowers last year. Prune all stems smaller than a pencil in diameter, cutting close to the ground. These thin weak stems will generally not produce flowers. Next cut back each remaining stem down to a strong vegetative bud growing from the stem. These are the buds that will produce strong stems and large flowers.
If you have a house hydrangea that never or seldom flowers, it most likely is a greenhouse forcing cultivar that is not cold hardy. Get rid of it
The Peegee hydrangea, which produces large white clusters of flowers, is generally grown as a small tree three to six feet tall. Prune this species in March or April around the main trunk. In time, this species develops a large head of branches.
The Hills of Snow hydrangea, Hydrangea arborescens Grandiflora, produces great mounds of white flowers growing on stems from a mound on the ground. Electric hedge clippers are the best tool to prune this species. Cut the stems as close to the crown as possible before the new growth starts in the spring. After the new growth has started, selectively hand prune the smallest and weakest buds and try to space the remaining buds three to four inches apart. This will result in the plants producing the largest and fullest flower heads. In late fall, the flower heads are great for making dry floral arrangements.
The oak-leaved hydrangea, Hydrangea quercifolia, is probably the easiest hydrangea to care for. You simply leave it alone unless there is an unwanted bothersome branch that develops. Choose oak-leaved hydrangea in blue, white and light pink or the cultivar Snow Queen, which produces large, white, cone-shaped flowers and attractive scarlet colored foliage in the fall.
All together, oak-leaved hydrangea is a species I think more people would plant if they knew its virtues.
Professor Emeritus Francis Gouin retired from the University of Maryland, where he was the state’s extension specialist in ornamental horticulture. Follow his column of practical gardening and plant advice every week, only in Bay Weekly. Ask Dr. Gouin your questions at firstname.lastname@example.org.