Azaleas are members of the genus Rhododendron, which is sometimes used as an umbrella term when referring to certain cultivars. They grow naturally as understory shrubs in deciduous woodlands in eastern North America. They are popular as general landscaping plants and for foundation plantings. Azaleas are typically slightly smaller bushes, with slightly smaller flowers and leaves, than the plants commonly called rhododendrons. The main difference between the two types, however, is that azaleas have deciduous leaves, and rhododendrons hold their leaves over the winter. Whatever the common name, all Rhododendron shrubs have similar planting and growing requirements.
Mimic azalea's natural growing conditions by choosing a shady site, or one that has morning sun and afternoon shade. Azaleas prefer loose, well-drained acid soil. If the soil tests 6.0 or higher, amend it with some composted pine needles or oak leaves, or add some peat to increase the acidity. Ferrous sulfate or agricultural sulfur may also be added to increase acidity.
When you plant your azalea, include the root ball soil, or the container soil mix if it is a pot grown shrub. Dig the planting hole 6 to 8 inches wider than the extended roots or root ball and just deep enough to accommodate the root ball. Your azalea should be planted so that the soil line on the trunk is the same depth as it was in the root ball or pot. One common problem when planting an azalea is setting it too deep in the soil.
Azaleas are sold in plastic pots or with burlap wrapped root balls. Before planting your new azalea, unwrap it or remove it from the plastic pot. Clean up the roots, removing some of the soil from them, especially if the plant is pot-bound in a plastic pot. Pot-bound roots and any root tips that appear dry or dead should be trimmed away. This pruning encourages new root growth as soon as the plant is in its new home. Azalea roots are fibrous and shallow, with most roots occurring in the top 4 to 6 inches of soil. This makes azaleas susceptible to damage from dry soil conditions.
Water and Mulch
Apply a layer of mulch about 3 inches deep around the newly planted azalea. Pine needles, shredded oak leaves or pine bark are acidic mulches that will benefit the azalea as they break down. Place the mulch in a circle that covers the entire area over the roots, and keep the mulch about an inch away from the trunk of the shrub. Check the soil under the mulch regularly, and keep it moist, but not wet, until the azalea is established. An azalea may need an entire growing season to become fully established.