What Is an Oakleaf Hydrangea?

Hydrangea quercifolia or oakleaf hydrangea is a flowering shrub native to stream banks and moist woodlands in the southeastern United States. Its natural range extends from Florida to Louisiana and north from Tennessee to North Carolina. Gardeners cultivate oakleaf hydrangeas as ornamental plants and value them for their large, showy blossoms and attractive foliage.

These deciduous shrubs can grow between three and 15 feet tall depending on the growing conditions and the cultivated variety, or cultivar. Most varieties have multiple stems and a rounded form. The older stems exfoliate, or peel back, to reveal cinnamon-colored inner bark.

Oakleaf hydrangea leaves, which range between three and eight inches long, strongly resemble oak tree foliage. Each leaf is dark green in color, with three to seven lobes, a coarse texture and serrated margins. The foliage changes to red, orange or purple in autumn.

During the summer, 10-inch-long pyramidal clusters of white blossoms appear. As the growing season continues, the white blossoms mature to pink and eventually fade to tan in the fall. Half-inch-long dry, oval-shaped brown fruits replace the flowers.

Oakleaf hydrangeas thrive in either full or partial sunlight. They grow best in nutrient-rich, well-drained moist soil and are hardy in United States Department of Agriculture zones 5 through 9. A layer of mulch around the base of the plant helps to suppress weed growth and to maintain the soil moisture and temperature. Oakleaf hydrangeas require little maintenance once established. They propagate by cuttings or seeds.

“Pee Wee” is a common Hydrangea quercifolia cultivar. This dwarf variety only grows between four and six feet tall and yields four-inch white flowers. “Harmony,” a larger selection, reaches heights of 10 feet and tends to yield heavy clusters of blossoms. “Allison,” one of the largest cultivars, reaches heights of 15 feet and produces foot-long flower clusters.

Homeowners cultivate Hydrangea quercifolia as specimen plants, borders or in naturalized settings. The oakleaf hydrangea is generally pest free, although several diseases like powdery mildew and botrytis blight occasionally damage the foliage. These shrubs are not especially winter-hardy and can suffer injury or dieback in zone 5. The leaves might sun-scald if exposed to harsh or intense sunlight.

In 1998, Alabama State Representative Gerald Willis introduced a bill that suggested naming the oakleaf hydrangea as Alabama's state wildflower. His first bill failed, but the Alabama House of Representatives and Alabama State Senate approved his second bill. The Governor signed it into law on 25 May 1999.