The showy, sterile corymb flowers are usually absent or if present they are usually less than 1 cm in diameter.[2] Flowering occurs May to July. The leaves are large (8 to 18 cm long), opposite, serrated, ovate, and deciduous. Smooth hydrangea can spread rapidly by stolons to form colonies. Smooth hydrangea is widely distributed across the eastern United States and was used medicinally by Native Americans, and later, by early settlers for treatment of kidney and bladder stones.