Azaleas come in thousands of varieties, according to the Azalea Society of America. You'll find evergreen and deciduous varieties, which can grow as shrubs, bonsai trees or as potted plants. Container-grown azaleas can be displayed indoors or out. Examine the roots of the potted azalea every six months, suggests the Azalea Society of America, and repot the plant when the roots become crowded and begin circling the pot. The New England Bonsai Gardens recommends repotting young azalea plants annually, and older plants every two to four years.
Cover the drainage holes of a pot that is about 2 to 4 inches larger than pot holding the azalea with an old coffee filter (or paper towel) to keep the soil from leaking out.
Fill the pot with 2 to 4 inches of specially formulated potting soil for growing azaleas, or combine equal parts of potting soil and fine pine bark. According to the University of Minnesota, a mixture of one part potting soil, one part sand (or perlite), and two parts peat moss can be used, or "any fresh potting soil rich in peat moss."
Remove the azaleas from the pot carefully to examine the root system. Cut off any frail, broken or tangled roots. The Azalea Society of America suggests loosening the roots (if possible), or making vertical cuts every 2 inches from the top-to-bottom of the root ball.
Place the azalea in the new pot and spread out the roots. Fill the pot with additional soil mixture to cover the top of the azaleas root ball. Gently pat the soil around the azalea plant.
Water the repotted azaleas thoroughly to settle the soil around the roots. Add more soil if needed, until the soil level around the azalea is the same height as previously.