 It produces large, showy, white to purple flowers each June and July.Rosebay rhododendron is the most frequently occurring and dominant species of "Rhododendron" in the southern Appalachian region, and occurs occasionally on mesic hill-slopes throughout the upper Piedmont Crescent of the Southeastern United States.Approximately 12,000 square miles in the southern Appalachians are occupied by this species where it dominates the understory.