Don Vandervort, Head Homeboy, has written more than 30 DIY home improvement books, been a segment host on HGTV, served as MSN.com's home improvement expert and written countless magazine articles.
Technically, azaleas are a type of rhododendron. But for all intents and purposes, they're treated as a separate plant group. Azaleas generally are smaller and sturdier than rhododendrons, with correspondingly smaller leaves and flowers. Varieties range from low-growing spreaders that can be used as ground covers to compact plants that do well in containers to tall hybrids that can double as small trees.
The most familiar azaleas are the evergreen hybrids, some of which are sold as florists' plants. There are a number of classes or groups of hybrids that have been developed over the years for specific climates and growth conditions. Belgian Indica, Brooks, Gold Cup, and Rutherfordiana hybrids do best in mild regions. Southern Indica hybrids can take more sun than most azaleas, while Kaempferi hybrids can handle temperatures down to -15 degrees F. Color choices are being refined, but most evergreen azaleas bloom in shades of white, pink, red, and purplish-pink. To be sure of color, buy plants when they are in bloom.
Deciduous azaleas provide color twice a year; their bright gold, orange, pink, and red flowers stand out in spring, and their foliage is equally brilliant in fall. Deciduous azaleas are generally hardier than their evergreen cousins--for example, Northern Lights hybrids can handle temperatures as low as -45 degrees F. If flower color is key, buy plants in spring; if you want fall foliage, choose plants in the fall.
Azalea species can also be found, though they are grown less often. The most well known include the torch azalea (Rhododendron kaempferi, a parent of the Kaempferi hybrid) and the snow azalea (R. macronatum).
A rhododendron can be a major focal point in a garden. Many of them are both large and bushy, though you can also find low-growing and dwarf varieties. Rhododendrons in bloom are covered with masses of large flowers in shades of white, yellow, pink, red, blue, and purple.
If you live where rhododendrons do well, you have your choice of hundreds of varieties. In marginal areas, your choices may be more limited, but there are still options. Ironclad hybrids are ideal for cold winter climates, whereas Vireyas are tropical plants that need frost-free conditions.
If you're buying from a nursery, you'll probably find the best selection when plants are in bloom. Not only is this a good time to plant, it's the best way to tell the flower color is what you want and that the plant is healthy and a good shape. If you want to mail order a plant, catalogs generally give complete descriptions, but be aware that photos may not reproduce the flower color exactly.
