Rhododendrons are shrubs known for their colorful and often fragrant flowers that emerge in spring. With cultivars in a wide range of sizes, shapes and colors, rhododendrons grow in USDA Hardiness Zones 4 to 8. The single or double clusters of flowers come in shades of pink, violet, lavender, red, purple, salmon and white. These shrubs, most of which are evergreen, grow best in moist, nutrient-rich soil and dappled amounts of shade.
Carolina rhododendron (Rhododendron carolinianum) is suitable for USDA zones 5 to 8. It has a rounded form and reaches a maximum height and width of 6 feet. The clusters of flowers emerge in mid-May and grow 3 to 4 inches long. Bloom colors include white, rose, pale rose and lilac. Carolina rhododendron has dark green leaves that when crushed are highly aromatic. The leaves are 2 to 3 inches long and develop a purple tinge in winter in colder climates. Carolina rhododendron grows best in part shade and moist, well-drained soil.
Catawba rhododendron (Rhododendron catawbiense) grows best in USDA zones 4 to 8. It is a wide spreading, dense shrub that grows 6 to 10 feet tall and 8 to 10 feet wide. The 5- to 6-inch puffball-like flowerheads emerge in mid- to late May to light up the garden with color. The blooms range from lilac and pale lavender to pink, with yellow to brown markings running down their throat for a showy contrast to the flower. Catawba rhododendron has 3- to 6-inch long leather-like leaves that are glossy and dark green. In winter the leaves develop a yellow tinge. Catawba rhododendron grows best in morning sun to bright shade and well-drained, moist soil.
Korean rhododendron (Rhododendron mucronulatum) is a slow-growing deciduous variety of rhododendron. It grows best in USDA zones 4b to 7. Korean rhododendron has an upright to oval form that is compact. The shrub can reach a maximum height of 8 feet and spread of 4 to 8 feet. Its single blooms are bright pink to purple and emerge in spring before the leaves pop out. The foliage is medium green and when crushed is highly aromatic. In fall, the foliage turns a fiery yellow, bronze and crimson. Korean rhododendron grows best in full sun to part shade and moist, well-drained soil.