Azalea is a shrub in the genus Rhododendron, a large genus that is known for its funnel-shaped fragrant, attractive flowers that come in a range of sizes, shapes and colors. Some azalea flowers grow in clusters while others are single. Azaleas grow best in fertile, acidic soil that is kept moist and within a pH of 4.5 to 5.5 and require a smattering of shade to flourish and thrive.
Coastal azalea (Rhododendron atlanticum) is a deciduous shrub native to the coastal regions of the Eastern United States. It has a slow to moderate growth rate and twiggy form. Coastal azalea grows to a maximum of 6 feet tall and has a spread of 3 to 6 feet. The fragrant, spring-blooming flowers on coastal azalea are funnel-shaped and grow in clusters along the shrub. The leatherlike green to powdery blue leaves on coastal azalea are oblong in shape and have a hairy midrib, or central vein, that runs down the center of each leaf. Coastal azalea grows best in full sun to part shade and well-drained, moist soil. Plant coastal azalea shrubs in USDA zones 5 to 9a.
Flame azalea (Rhododendron calendulaceum) is a slow-growing deciduous shrub that has an upright, loosely branched form and coarse texture. They reach a maximum height of 8 feet and have a spread of 8 to 10 feet, ideal for creating a privacy screen along the landscape. Flame azalea has 2-inch-wide funnel-shaped flowers that emerge in spring and range in colors from orange, pink and scarlet to apricot, salmon and gold. The glossy, oval-shaped leaves on flame azalea contrast with the bright blooms for striking display. Flame azalea grows best in part shade with some direct sun and well-drained, moist soil. They are also drought-tolerant. Plant flame azalea in USDA zones 5 to 7.
Florida azalea (Rhododendron austrinum) is a deciduous shrub that is suitable to grow in USDA zones 6 to 9. It has an upright form with irregular, loose branching and grows between 6 and 10 feet tall and has a spread of 4 to 6 feet. The funnel-shaped, spring-blooming fragrant flowers on Florida azalea grow in dense clusters of eight to 15 flowers per cluster and attract hummingbirds and butterflies to the garden. Each flower head on Florida azalea grows 3/4 inch long and ranges in color from peach and orange-red to yellow. The dull green 4-inch-long leaves are oval to elliptic in shape. Florida azaleas grow best in open shade to sun-dappled shade and well-drained, acidic soil that is sandy.