Rhododendron yedoense Maxim. var. poukhanense Korean Azalea Size: 3 to 6' high and spreads that much or more. Hardiness: Zone (4)5 to 7. Habit: Develops into a broad mat on exposed locations. Foliage is dark green in summer; orange to red-purple in fall. Rate: Slow. Culture: Sun or part shade.