Two hydrangea species are native to the southeastern United States — Hydrangea arborescens and Hydrangea quercifolia. Both are bold-textured, deciduous shrubs which produce small, fertile flowers. Many selections are considered more garden-worthy than the native species because they display large, sterile florets.
Hydrangea arborescens, commonly called wild or smooth hydrangea, will achieve a height of 3 to 4 ft and a spread of 3 to 5 ft. The flowers are displayed atop vigorous canes in mid-summer. The flowers start green, turn white, then brown and persist on the plant for some time. Because flowers appear uniformly at the same height, plants are often managed by pruning back to near the soil surface in winter or immediately after flowering in mid-summer.
The cultivar with the largest (sometimes over a foot in diameter) and most uniform inflorescene of sterile florets is Annabelle. A similar plant having large but less uniform sterile flower heads is Hydrangea arborescens var. grandiflora sold as ‘AG’ or ‘Hills of Snow’. Flower heads can be used as fresh flowers during the summer or harvested and hung upside down to dry in dark, well ventilated areas. Dried flower heads are popular in fall and winter floral designs.
Hydrangea quercifolia is commonly called oakleaf hydrangea because the leaves are shaped like oak leaves. Panicles of flowers are produced in mid-summer. Flowers open creamy white then fade through pink and green to brown.
Oakleaf hydrangea can be grown in sun or shade and prefers a rich, moist soil. If planted in mostly sun, I feel this hydrangea makes a lovely privacy screen. Leaves are 4 to 6 inches long and turn purple in autumn when grown in full sun but may be tissue paper thin, well over a foot long, and turn orange-red in autumn when grown in deep, moist shade in the mountains. Height varies from 3 to 8 ft., occasionally taller. The irregular spreading shrub can reach 8 ft in width.
The most popular cultivars are Harmony, Alice, and Alison. ‘Alice’ is a vigorous cultivar with white flower heads over a foot long. ‘Pee Wee’ and ‘Sykes’ are compact forms only reaching about 3 to 4 ft tall at maturity. H. arborescens can be grown in full sun or light shade while H. quercifolia is best grown in partial to full shade. Both will grow in normal to moist soils with a 3- to 4-inch layer of mulch. Hot, dry sites should be avoided. Occasional insect and disease pests will attack either species, but pest control is rarely warranted on properly sited plants. Transplanting is relatively easy and the growth rate is rapid.
Fertilizer needs are minimal. Care should be taken to establish a soil pH between 5.5 and 6.5. An annual maintenance application of 1 lb of actual nitrogen per 1,000 ft2 should be applied in late winter beginning the year following planting. Pruning, when necessary, should be done immediately following flowering or during winter for both Hydrangea species.
Erv Evans, Extension Associate
Richard E. Bir, Extension Specialist
Department of Horticultural Science