Native azaleas are a group of flowering bushes native to North America. They are members of the rhododendron genus but form a distinct sub-group within that genus. Plants in this genus are part of the heath family and are related to blueberries and mountain laurel. Sometimes called bush honeysuckle, native azaleas differ from other members of the genus in growth habits, and leaf and flower characteristics. Native azaleas bloom in a wide range of colors and different species bloom at different times.
There are 17 species in the native azalea group, all but two of which are found the eastern or southeastern part of the US; Rhododendron occidentale and Rhododendron canadense are found in the northwest of the country. All of the species attract butterflies and some also attract hummingbirds. Flower colors often found on native azaleas are shades of white, pink and yellow as well as orange and red. Many of the species have fragrant blossoms, and at least one species within the group is in bloom from early April into late August or early September.
Native azaleas are found from the deep south, where winter temperatures are mild, to parts of the country where temperatures regularly dip below freezing and snow often falls. Although some grow naturally in areas with constantly moist soil many do not tolerate wet ground well. Some species are found in very dry soils including clay and sandy areas. All azaleas grow best in acidic soil.
Species found for sale in nurseries should be planted in well-drained acidic soil and watered regularly. They grow best in partial to full sun. The flower buds for the next year are set after blooming stops, so pruning is best done as soon as possible after the blooms die back.
Although azaleas are closely related to rhododendrons there are noticeable differences between the two kinds of plants. Rhododendrons are almost always evergreen; some azaleas are evergreen but all those native to North America are deciduous. The flowers on rhododendrons grow in sprays, called trusses, while azalea blossoms are solitary. Azalea blossoms usually have five stamens while those of rhododendrons have ten or more.
In contrast to rhododendrons, azaleas have a more open growth pattern. They are shorter plants, usually no more than 8 feet (about 2.4 m) tall while rhododendrons are more upright and may be as high as 80 feet (about 24 m) tall. Rhododendrons generally have large leathery leaves while those of azaleas are smaller and thinner.