There are two species of hydrangeas that are native to the United States:

Oak leaf hydrangea ( Hydrangea quercifolia). It is native to the Southeastern United States. Panicles of flowers are produced in mid-summer. Its flowers open creamy white then fade through pink and green to finally to brown. It can be grown in shade or full sun. When grown in sun the leaves turn an attractive purplish color in the fall. There are a number of cultivars available: 'Alice' produces very large, long flowers. 'Pee Wee' is a compact form.

Smooth or wild hydrangea (H. arborescens). It is native to the eastern U.S. from New York to Florida and west to Iowa and Louisiana. It grows well in part shade. This species can grow to quite a large size (height of 3 to 4 ft and a spread of 3 to 5 ft) although it may die back in winter in colder areas. It produces large flowers, which on the cultivar 'Annabelle' can be a foot in diameter.

Silverleaf hydrangea (H. aborescens subsp. radiata) is a subspecies of wild hydrangea found in several U.S. states in the southern Appalachians.  It is a fast growing shrub at home in light shade, growing to about 4 feet by 4 feet.  In addition to white flowers in summer, the silvery underside of its leaves is visible in the breeze.

Courtesy of NYBG Plant Information