To ensure a successful azalea planting, cultural requirements, planting techniques, and maintenance should be well understood.
Exposure. Azaleas prefer a cool, partially shaded site. Several varieties can tolerate full sun, but most prefer an area that is not exposed to long periods of hot full sun and drying winds.
Soils and Planting. Azaleas grow best when planted in acid, well-drained soils with a pH near 5.5. A soil rich in organic matter is ideal for azaleas. Many people mistakenly believe that digging a planting hole 3 or 4 times larger than is needed, adding crushed rock to the bottom and rich topsoil as a backfill will solve all drainage problems. Holes dug in poorly drained soil will only fill with water and continue to hold this excess over a long period of time regardless of the size of the hole. When soils are saturated, the amount of oxygen available to roots becomes very limited.
Generally, a raised bed is recommended. The planting area should be elevated to ensure good surface and internal drainage. Sometimes a hole should not be dug the plant should just be planted at grade level. The area around the root ball should be built up with topsoil and plenty of organic matter. The organic matter can be decayed pine bark, sawdust, organic compost. Fertilizer should not be added to the backfill at time of planting.
When planting balled-and-burlapped plants, it is necessary to remove nylon strings or wire from the root ball. The burlap can remain around the root ball but the plastic liner inside the burlap must be removed. Many container-grown plants will become pot-bound and will require special attention before planting. The layer of matted roots around the outside surface should be cut, loosened, or frayed out before planting. If not, the roots will fail to grow out into the surrounding soil, and plants will be more susceptible to drought.
Watering. Watering newly planted azaleas is essential. If planted in a well-drained soil rich in organic matter, frequent watering will be required. Backfills dry out much faster than the original soil around the plant. It is important that water not be applied in quantities that will waterlog the media.
Mulching. A 3- to 4-inch layer of organic mulch around azaleas is recommended. This will help to discourage weeds, prevent soil crusting, hold moisture during dry periods, and maintain a more uniform soil temperature.
Fertilizer. Azaleas grow best with a moderate, even level of fertility. Several special azalea fertilizers are available; they are excellent when used at recommended rates because of their slow-release ability. Satisfactory results can be obtained from an 8-8-8 or 10-10-10 analysis. Over-fertilization can cause severe damage. Therefore, split applications should be made in March, May, and July. Small plants, those less than 12 inches in height, should receive 1 teaspoonful per application. For larger plants, a level tablespoon per foot in height should be sufficient. For large bed areas, 2 to 3 pints per 100 square feet can be broadcast. Maintaining the correct pH (between 5 to 5.5) and fertilizer requirements can only be determined by soil testing.
Pruning. Contrary to popular opinion, many azaleas do need pruning. Pruning is especially desirable to produce more compact growth for tall-growing cultivars. Heavy pruning should be done immediately after the flowering period. Tall, rangy limbs that appear in the top of the plant should be removed down inside the body of the plant. To induce branching, it is useful to pinch out tips of new growth between flowering and the first of July. Later pinching will reduce flower production the following year. Dead or injured branches must be removed when shaping or heading-back azaleas.
Dwarf azaleas also benefit from pruning. This gives better shape and improves flower clusters on established plants.
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