Azaleas and rhododendrons are the mainstays of woodland gardens. There are hundreds of varieties to choose from, ranging from ground covers to towering shrubs. They’re naturally well formed, requiring little in the way of pruning and shaping, and their foliage is beautiful, bringing them to the forefront of any garden even when they are not in bloom. In spring, they’re stunning, with their masses of blooms in shades of white, gold, pink, red, and blue.
Azaleas (shown at right) are technically a type of rhododendron, but for all intents and purposes they’re treated as a separate plant group. Azaleas generally are smaller and sturdier, with 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 foliage colors are important to you, 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).
Azaleas are the more adaptable of the two plants. They can be grown along most of the West Coast and into eastern Washington and Idaho; there are even some small areas in Utah and Colorado where they’ll thrive.
Their growing range in the eastern half of the country is even larger, stretching from Maine to Michigan in the north and from central Florida to Texas in the south. Not all varieties will grow in all places, but you’re sure to find plants that will work in your garden.
Rhododendrons (shown at right) 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 are more limited, but there are options. Ironclad hybrids are ideal for cold-winter climates, while 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 but it’s also 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 and websites generally give complete descriptions, but be aware that images may not reproduce the flower color exactly.
Rhododendrons thrive in fewer parts of the country than do azaleas, but where they do grow they are spectacular. The Pacific Northwest and along the northern California fogbelt are two prime locations.
In the eastern United States., rhododendrons do well along the coast from Maine to northern Virginia and grow inland as far west as the southern Great Lakes and south along the mountains to northern Georgia.
Hardier rhododendrons are being grown from Ohio to Illinois and through southern Missouri to northern Louisiana, Mississippi, and Alabama.
In the west, these same rhododendrons are making appearances in gardens in the Central Valley of California, around Salt Lake City, and near Denver.