Azalea Planting Zones & Care

Preferred Hardiness Zones

• Azaleas prefer moderate temperatures for growth, thriving primarily in U.S. Department of Agriculture plant hardiness zones 6 to 8. Some varieties can survive in climates as cold as USDA zone 4 with extra mulching in winter. As azaleas make good container plants, they can be grown outdoors in colder climates, then brought inside during the winter. Even within the preferred zones, however, some varieties will not grow well due to local microclimates. Always check with your local university extension or garden center to determine which varieties are appropriate for your area.

Planting, Site Selection

• Select a partially shaded site high in organic matter with slightly acidic soil registering a pH of 4.5 to 6.0. Azaleas grow well near oak, pine and holly trees. Exposure of morning sun and afternoon shade is ideal. Although these plants like moist soil at their roots, planting areas must have good drainage as azaleas can be damaged by excessive moisture. Before planting, water the root ball thoroughly. Dig a planting hole two to three times wider than the root ball and thoroughly mix organic matter such as pine bark or compost into the hole along with the plant. Because azaleas are shallow-rooted plants, the hole should only be as deep as the root ball. Backfill with soil and firmly pack the area by hand to minimize settling.

Water and Fertilization

• Azaleas’ shallow roots require frequent irrigation. When soil is dry, water thoroughly to a depth of 8 to 10 inches once a week. Use a drip irrigation or a soaker hose as overhead watering can promote disease. Make sure that a 2- to 3-inch layer of mulch covers the base of the plant at all times to retain soil moisture. Compared to other shrubs, azaleas have low nutritional requirements. Organic amendments incorporated into the surrounding soil when planted, along with organic mulch, are usually enough to meet nutritional needs. When needed, use controlled-release, acid-forming fertilizer such as cottonseed meal or commercial azalea food early in spring just after flowering.

Pruning

• The best time to prune azaleas is in spring just after they bloom. Avoid pruning after July 1 when buds form for the next season. Choose from two techniques: heading or thinning. Heading is the indiscriminate cutting back of branches to reduce size, create a specific shape or renew overgrown plants. Thinning involves complete removal of branches back to another branch, bud or main trunk. This method is preferred because it opens the canopy by eliminating leggy branches, improves airflow and helps minimize disease.