Overpruning Hydrangeas

Types

• There are approximately 70 species of hydrangea. In American gardens, a limited number of species, but numerous cultivars of these species, are grown. Bigleaf hydrangeas (H. macrophylla) and mountain hydrangeas (H. serrata) should be pruned back by no more than 50 percent in early to mid-spring, or immediately after flowering ends in summer. Cut back only a portion of all branches so dormant flower buds may form from midsummer to fall for the following year. Prune others, such as panicle hydrangea (H. paniculata) and oakleaf hydrangea (H. quercifolia) to no shorter than 18 inches in late winter before any leafy growth appears. Conduct climbing hydrangea vines' pruning after flowering ends.

Pruning Necessity

• Pruning is not needed on hydrangeas for them to bloom or grow in good health. Rather than worrying about if or when the hydrangea bushes in the garden need pruning, you can take a laissez-faire approach. If the hydrangea bush is healthy, refrain from pruning. The plant will manage to produce flower buds and bloom at the appropriate time of year. Always strive to remove dead or broken branches from hydrangeas. After a brutally cold winter, dead branches look paler brown and shriveled and feel lighter and brittle.

Overzealous Pruning

• Hydrangea bushes need their foliage in summer to produce carbohydrates to fuel plant growth and metabolism. Conducting a severe pruning in late winter or early spring won't harm a hydrangea, as it will sprout new foliage and rejuvenate. However, do not overprune hydrangeas after midsummer -- August 1 in the United States -- because foliage is removed and the roots must expend lots of energy reserves to grow new stems and foliage. Late-season pruning stresses the hydrangea, making it more susceptible to frost damage in fall and dieback in the subfreezing temperatures in winter, including killing carbohydrate-deprived roots.

Correcting Problems

• If you feel you overpruned your hydrangea shrub, leaving the plant alone for 18 to 24 months may prove the best maintenance strategy. Continue to irrigate or fertilize with your regular regimen, but do not conduct any more pruning with the intent of correcting your overpruning mistake. The shrub must rejuvenate. Depending on the plant species, it may or may not bloom. Only if dormant, mature flower buds survived the overpruning event will flowering occur that year. After one more year of growth -- and no more pruning -- the hydrangea will have mature stem tissues to again bear an abundant crop of flowers. Pruning always leads to more side branches, with more numerous branch tips that yield more flower clusters.