The azalea is a member of the rhododendron family and a staple of gardens around the world. There are more than 10,000 types of azaleas registered, but only a few are typically available in commercial nurseries. Some of these are hybrids that fall into two basic categories: evergreen and deciduous.
Evergreen azaleas are native to Asian countries such as Japan, and these types of azaleas are the most common. There are two sets of leaves on evergreen azaleas; one set falls off in the spring and the other set falls off in the fall. Flowers measure 2 inches (5 cm) in size and bloom in bold colors such as pink, red, orange, white, chartreuse and purple. There are not yellow flowers. Indica or Indian, Glen Dale and Kaempferi are three common varieties of evergreen azaleas.
Deciduous azaleas that are native to North America are very common in the southern United States and also grow in some parts of Asia. In the United States, these types of azaleas also are sometimes called native azaleas. They bloom in the spring and the leaves fall in autumn. Blooms come in bright pastel colors including pink, red, purple, yellow, white and orange. Some common names for deciduous azaleas are Flame, Alabama and Honeysuckle.
An azalea is either a species or a hybrid. Species azaleas are those that grow from another azalea through pollination and seeds. Azaleas that are species azaleas have not been exposed to other types of azaleas, so there is no crossbreeding. These azaleas prefer a moderate climate, high humidity and rich soil that drains well. They are not as hardy as hybrid azaleas and can easily die when there are extreme changes in conditions.
A hybrid azalea is a cross between an azalea and some other kind of plant. Hybrids can only grow from a cutting of another hybrid. Caring for azaleas has been made easier with the introduction of hybrid varieties, because conditions do not have to be ideal for the plants to thrive. Many hybrids are resistant to extreme temperatures, sun and drought but can be prone to problems when they are grafted with another plant. The three largest groups of hybrids are the Kurume, Belgian Indian and Southern Indian, with several varieties in each group.