To insure a successful azalea planting, cultural requirements, planting techniques, and maintenance should be well understood.
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.
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 folks mistakingly 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 -- irregardless of the size of the hole. When soils are saturated, the amount of oxygen available to roots becomes very limited.
Generally, it is recommended to prepare a raised bed. Elevate the planting area to insure good surface and internal drainage. Sometimes a hole should not be dug -- just plant at grade level. Build up around the rootball with topsoil and plenty of organic matter. The organic matter can be decayed pine bark, sawdust, organic compost. Do not add fertilizer to the backfill at time of planting.
When planting balled and burlapped plants, be sure to remove any nylon strings or wire from the rootball. The burlap can remain around the rootball but be certain there is not a plastic liner inside the burlap. Many containerized 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 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. Be sure not to apply quantities of water that will waterlog the media.
A 3-4 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.
Azaleas grow best with a moderate and even level of fertility. There are several special azalea fertilizers available which are excellent when used at recommended rates because of their slow release ability. Most homeowners will get satisfactory results 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, 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, 2-3 pints per 100 square feet can be broadcast. Maintaining the correct pH (somewhere between 5-5.5) and fertilizer requirement can only be determined by soil testing.
Contrary to popular opinion, many azaleas do need pruning. Pruning is especially desirable to produce more handsome and compact growth for tall-growing cultivars. Any 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, pinch out tips of new growth between flowering and the first of July. Later pinching will reduce next year's flower production. Always remove any dead or injured branches 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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Last modified: Nov. 12, 2014, 1:01 p.m.