Two valuable floriferous shrubs or small trees that can give gardeners anxiety about pruning procedures are hydrangea (Hydrangea spp.) and crepe myrtle (Lagerstroemia indica), also called crape myrtle. Pruning done improperly or at the wrong time of year robs you of blooms the next season and can even affect the long-term health of the plant. For hydrangeas, you have to know what kind of hydrangea you have and when it blooms. For crepe myrtle, you need to understand how the plant grows and how to enhance its natural shape to encourage greater summer bloom.
Hydrangeas produce showy clusters of large white, pink or blue flowers that provide a colorful display against large green leaves. Depending on the type, they form large shrubs to small trees. Native to Asia and North America, they bloom in spring and summer and go dormant for the winter. The blooms are used as cut flowers and in dried arrangements. For pruning purposes, there are three types of hydrangeas. First are the species that bloom on the current season’s growth, or the new growth. Then there are those that bloom on last season’s growth, or the old growth, and the third type, the endless bloomers, grows on both old and new growth.
New-wood bloomers such as summer-blooming “PeeGee” (Hydrangea paniculata “Grandiflora”) and spring-blooming “Annabelle” (Hydrangea arborescens) can be pruned in late winter. For really large blooms on “PeeGee,” cut stems back to within 12 inches of the ground. For more abundant but smaller blooms, cut stems back to 18 or 24 inches to provide a sturdy framework for the new flowers. Old-wood bloomers include bigleaf hydrangea (Hydrangea macrophylla) and oakleaf hydrangea (Hydrangea quercifolia). Cut them back in early summer just after the current year’s flowers fade. They will branch out sooner with the wood that will bear the next season’s flowers. Prune endless bloomers such as cultivars of bigleaf hydrangea “Endless Summer” and “Forever and Ever” (Hydrangea macrophylla cultivars) in the fall if cutting back is needed to control plant height or shape the bush. “PeeGee” grows in U.S. Department of Agriculture plant hardiness zones 3 through 8, “Annabelle” in zones 3 through 9, bigleaf hydrangea in zones 6 through 9 and oakleaf hydrangea in zones 5 through 9.
Crepe Myrtle Characteristics
This small deciduous tree is native to China and Korea and can reach 25 feet tall in USDA zones 7 through 9. It is usually multitrunked but can be trained as a standard tree. Cultivars offer dwarf, semi-dwarf and small and large tree varieties. In summer the tree produces masses of flowers in colors of white, pink, red, rose, lavender and purple. Fall foliage can be yellow, red, orange, purple-red or maroon. Smooth, mature bark flakes off in patches, revealing varying shades of brown and gray. Crepe myrtle needs full sun and well-drained soil.
Crepe Myrtle Pruning
Shape crepe myrtle as it grows to have three to seven main trunks. If you want to be able to walk under the tree, keep trunks straight up to 6 to 8 feet off the ground, and then allow branching. Prune crepe myrtle in the late winter while the tree is still dormant so you have better visibility of branching structure. This also won’t affect the next season’s bloom, which will appear on the new growth. Prune branches back to the main trunk or branch without leaving a stub. Remove branches that cross or rub against each other or that are growing too close together to open up the canopy. Remove any branches smaller than a pencil in diameter so larger branches can afford to make more growth and numerous flowers.
Cathryn Chaney has worked as a gardening writer since 2002. Her horticultural experience working in the nursery industry informs her garden articles, especially those dealing with arid landscaping and drought-tolerant gardening. Chaney also writes poetry, which has appears in “Woman’s World” magazine and elsewhere. Chaney graduated from the University of Arizona in 1992 with a Bachelor of Arts in English.