Rhododendrons and azaleas, both from the genus Rhododendron, have long been mainstays of late spring because of their spectacular clusters of showy blooms—plus, large green leaves that often stay green through winter.
The flowers are tubular-, funnel-, or bell-shaped—and often fragrant. The leaves of the smaller azalea are usually pointed and narrow; the leaves of the rhododendron are generally large and leathery.
These shrubs prefer climates with adequate rainfall and moist summers. The two main azalea groups, evergreen and deciduous (varieties that drop their leaves in the fall) can be found in nearly every part of North America, from the frosty Canadian plains to tropical Florida. The rhododendron types are fussier, preferring environments where it is neither too hot nor too cold (Zones 5 to 8). They need a certain amount of chilling to develop strong flower buds.
With thousands of varieties, there are rhododendrons and azaleas for just about every landscape situation. There are low-growing ground cover azaleas, plants that grow from 1 to 2 feet, as well as plants that can grow up to 25 feet tall. They come in many flower colors, including pink, red, white, yellow, and purple. Though most plants flower in the spring, there are also summer-blooming varieties that add color and charm to the garden.