The genus Rhododendron, which includes all azaleas and rhododendrons, comprises more than 1,000 species worldwide. The majority of all 70 species of azaleas are indigenous to the Northern Hemisphere, with a range from North America to Europe and Asia. Deciduous azaleas, which lose their leaves in winter, are native to eastern Asia, Europe and North America, while evergreen azaleas are found growing naturally only in Asia. Asian azaleas are generally not as hardy and are often crossed with hardier European or North American species.
Deciduous azaleas tend to have an open, loosely branched habit. Evergreen azaleas have either an upright or sprawling habit and tend to be more densely branched than deciduous azaleas. Evergreen azaleas often have wide showy flowers that are disproportionately large compared with the foliage while deciduous azaleas have long tubular flowers that are in proportion to the foliage. The flowers on deciduous azaleas shrivel up and shed quickly while evergreen azaleas tend to hold on to their flowers after they turn brown and can look a little messy.
Evergreen azaleas are dimorphic, meaning they have two kinds of leaves. One set of leaves appears in spring around flowering time. They last for the season and then yellow and fall off in autumn. Another set of leaves is formed in early summer. These leaves last for 1 – 3 years and are thicker and smaller, and leathery.
The typical azalea flower has five petals that are fused at the base and flare out at the tip to create either a star- or butterfly-like appearance. Usually the flower has 5 to 10 stamens (the male reproductive part) that are often showy. Deciduous azaleas have long tubular flowers and evergreen azaleas have shorter tubes and a wider appearance.
Sometimes the single flower of an azalea can be modified when either the stamens (the male reproductive structure) or the sepals (modified leaves that protect the flower buds) are transformed to look like petals. Hose-in-hose is a term used when the sepals are ornamental and look like petals. The result is the azalea taking on the appearance of a flower within a flower. Double describes a flower in which the stamens have changed into a petal-like structure. It looks like the inside of the flower is filled with petals. Semi-double refers to a flower in which the stamens are only partially changed.
The late spring crescendo of white, coral, pink and purple blossoms in the Azalea Garden is one of the New York Botanical Garden’s most striking seasonal spectacles. By selecting from the tabs above, you can learn more about some of the species and cultivars of Azalea you may find at the NYBG.