There are two kinds of Azaleas in the Rhododendron genus: deciduous and tropical evergreen. They are botanically classified as sub-genuses of the Rhododendron genus with evergreen species falling under Tsutsutsi and the deciduous species under Pentanthera. If you have a tag on your plant with one of these genus names followed by a cultivar and variety, you'll know which you have. There are more than 10,000 known species, cultivars and hybrids of Azalea in varying colors, flower forms and sizes. If you have no information to go on but the plant itself, you can determine the difference by evaluating a few clues.
Inspect the plant size and life cycle. Deciduous Azaleas bloom in later spring, tend to be larger shrubs with an open branch structure, and have ovate dark green leaves that turn to red, gold or rust in the fall before being shed.
Observe the leaf structure. On evergreen Azaleas, there are two sets of leaves: a larger lighter-green spring and summer set, followed by the development of a darker, smaller and more leathery set. The two sets often are seen together on the plant at the same time. Deciduous Azaleas have just one set with one type and size of leaves.
Determine the plant source as a clue to type. If the Azalea was delivered by a florist or is shaped into a decorative small topiary tree, or was purchased in full bloom from your local grocery store in the dead of winter, it likely is a greenhouse-grown evergreen Azalea. This means that unless you live in USDA zone 8 or higher with frost-free temperatures, the plant needs to live indoors during most of the year with bright, indirect light.