Preparing soil properly is the basis for successful azalea culture. Beginners do not always realize how important soil preparation is, and the azaleas they plant often grow poorly. The only way to know what nutrients your soil needs for growing azaleas and whether the soil pH level needs correcting is to have a soil test. Get information and supplies for soil testing at your county Extension office.
For good results, spend about the same amount of money for organic material as you spend for azalea plants. Organic matter does several important things for the root growth of azaleas. It loosens and aerates tight clay soils; and, loose sandy soils can usually hold more water for a longer period of time with the introduction of organic matter.
There are several good organic materials. Peat moss is ideal for azaleas and is probably the best to use. Ground pine bark is also very good. Leaf mold from the woods and composted leaves are satisfactory.
Sawdust is used by a number of Alabama nurserymen. However, using sawdust may rob the soil of its nitrogen supply during the first and second growing seasons. If this happens, the leaves will turn a light yellow. This discoloration can be corrected by light applications of nitrogen during the growing season, in addition to regular fertilization.
Peat moss is best to use, followed by pine bark, leaf mold, and then sawdust.
Before planting, space plants out based on their ultimate mature size. A common mistake is to plant azaleas too close together. The result is plants that lose their character, are harder to maintain, and are more prone to insect and disease problems.
Water azalea plants in the container to increase plant water content before planting.
If you are planting a bed of azaleas, put 5 to 6 inches of organic matter on the surface. Then work it in to a depth of 12 inches.
If azaleas are to be planted in individual holes rather than beds, dig each hole shallow and wide, at least 24 inches wide or 2 to 3 times the width of the container. The hole should be a depth that will allow the top of the root ball to stick up about 12 inch above the surface of the surrounding soil. Use only the native soil to fill the hole.
Deep planting often causes stunted growth or it may even cause the plant to die. Set the plant in the hole and add soil, lightly firming it around the root system. When the hole has been filled, water it thoroughly to further settle the soil. The goal is to remove air pockets around the roots and not to "pack" the soil. Structure and valuable air space are often lost in packing, and the plant suffers. On a slope or in a well-drained soil, make a saucer-shaped depression around the plant to hold water.
Mulching is very important in azalea culture because it keeps the soil from drying out too fast. Pine straw is excellent mulch and is usually easy to get. Ground pine bark is also good. Slightly rotted tree leaves can be used.
Avoid using black plastic to mulch azaleas, but landscape fabrics are acceptable as those materials allow better air penetration into the soil than black plastic.
Spread the mulch out beyond the outer leaves of the plants. After settling, mulch should be 2 to 3 inches deep.
Azaleas must be watered during dry periods and after initial planting. September and October are especially important times to supply water. You won't need to water as often if you have planted properly, because correct planting promotes good root development. A good mulch also helps to reduce the amount of water you will need to use as well as the number of times you have to water. If a mulch is used, a heavy watering once a week should be enough during dry periods. Two to three times a week for the first 6 to 8 weeks after planting would be beneficial.
A big problem in azalea culture is over-fertilizing, especially with phosphorus. Too much fertilizer injures the plants and may even cause them to die. Be particularly careful with small plants. Use no more than 1 teaspoon of fertilizer at a time on plants less than 12 inches tall. For larger plants, use 1 heaping tablespoon per foot of height. Scatter the fertilizer under the plant on top of the mulch. It is better to make a light application after blooming and another in July than to apply the yearly recommendation all at one time.
The best way to avoid over-fertilizing your azaleas is to have your soil tested every 2 or 3 years and follow the recommendations. If you don't have a soil test, use an all-purpose fertilizer, such as 8-8-8 or 12-6-6, on soils with medium or low fertility. Some special azalea-camellia formulations cater to the acid soil requirements of these plants with part of the plant nutrients in a slow-release form. In many cases, these are very good for azaleas. Many nurserymen have gotten excellent results with fertilizers containing two parts nitrogen to one part phosphorus and one part potassium, especially when part of the nitrogen is in slow-release form.
If your soil fertility is high, you only need to use nitrogen.
Azaleas can be pruned without damaging the plant and without interfering with future flower production. Nurserymen begin pruning when the plants are small to create a compact, branching growth habit.
In Alabama many azaleas begin to set flower buds in July. Therefore, pruning after early July may reduce the next year's flower production. The best time to prune is soon after the flowering period in the spring. Cut out the limbs that have grown out of the main body of the plant. Do not shear unless your intention is to create a formal hedge, spalier, or topiary plant. Shearing destroys the natural form of the plant.
Azaleas often become too large for the area they occupy, especially when they are used as foundation plants around a home. If this happens, cut back the large plants to 6 to 12 inches above the ground shortly after blooming. When new growth buds appear on the stem, the new stems and leaves will grow very fast. Pinch out any long unbranched shoots that develop to force a branch system. Be sure to keep the soil moist for several days after severe pruning.
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