by Ken Gohring
After the rhododendron or azalea is located in the ground, it is important to properly mulch the plant. Good mulching materials include pine bark in various sizes particles, pine straw, wood chips, leaves and other materials preferably organic in nature. Avoid using materials with small particles like saw dust as well as peat moss, which will become quite dry and be very restrictive to the passage of moisture to the plant's roots. The larger sized mulching material is superior to smaller sized material. Pine bark mulches are usually available in three sizes. When wood products like wood chips and bark are used, it is advisable to add nitrogen to the material in some degree as the wood decays and leaches nitrogen from the soil. Mulch material decay is helpful to plant growth, as the plant's roots will eventually grow into the material. Cypress and cedar are good mulch materials but unlike other wood materials, they do not decompose as rapidly.
Mulch should be applied from 2 to 4 inches deep. At times, it is necessary to monitor plants because the mulch materials will wash away from large rainfalls. Mulch should be applied in such a way that it encircles the plant's extended roots. An area up to 3 inches immediately adjacent to the plant's stem should not be covered. Mulch helps plants in several ways, but its primary function is to help keep the plant's root zone from becoming dry. In addition, mulch helps keep down weeds growth and prevents root damage in extremely cold periods.
Rhododendrons and azaleas will profit from light fertilization. However, more plants are lost from over fertilization than from the lack of fertilizer. If the soil they are planted in is relatively fertile, the plants will do well without fertilization. However if the plants are located in less fertile soil, use of acid loving fertilizer is recommended in late winter or early spring. Some recommend fertilization after spring bloom. Special fertilizers formulated for acid loving plants are best for rhododendrons and azaleas. These fertilizers are usually slow-release fertilizers that provide supplements for plants over a longer period than regular fertilizers. While these fertilizers are more expensive, they do not tend to damage plants as badly as other fertilizers. Cottonseed meal is an organic fertilizer that is frequently used. Others use liquid fertilizers. Generally, the liquid fertilizers, in varying degrees of dilution, can be used for rhododendrons and azaleas in various states of their growth. Fertilization after June is too late and should be avoided.
Other Plant Maintenance
In addition to fertilization, other activities to ensure healthy plants are observation of leaf color and overall appearance. When rhododendrons and azaleas lack magnesium or iron, their leaves show a yellow colorization between the leaves green veins. If this coloration appears on the plant's older leaves, the deficiency is magnesium. A similar colorization on younger leaves indicates iron deficiency. Epsom salts can be spread around the plant to help with the magnesium deficiency. A temporary fix for iron deficiency is the use of ferrous sulfate added to the soil or cletated iron sprayed on the plant's leaves. If the lack of iron persists, a more permanent fix is replanting and soil content modification. The lack of iron is usually caused by lack of acidity in the soil. Another problem with rhododendrons and azaleas is lack of moisture, which is indicated by curled or drooping leaves. Moisture problems and treatment for diseases and pests is discussed below. It is also important to prune dead branches from plants. This can be done at any time but pruning to shape plants is recommended during and after bloom time, before the set of next year's flower buds. Weeds around plants should be pulled rather than hoed because of the shallow nature of the azalea and rhododendron roots.
New plants will likely require periodic watering the first two years of their growth, particularly during the hot summer months. It takes some time for a rhododendron or azalea roots to spread from their original root ball into the soil surrounding it. Their roots, due to their fine structure, take longer to grow out than other kinds of plants... Consequently, it is important to keep the original root ball moist. One recommendation is to use a dripping hose at the trunk of the plant for a few hours weekly in addition to a regular watering program for the plants the first year.
Lack of water to an extent that a plant is stressed, is reflected in its leaves. This results in drooping or curling leaves. This stress condition is best determined by examination the leaves in the morning. If the condition is present, the plant should get a good soaking. Regular weekly watering practices will help prevent stressed plants. One good approach is a drip system, which can be operated for a few hours periodically to provide water in a slow consistent manner providing moisture for plants. Such drip systems prevent waste of water, are relatively inexpensive and have proven to be quite effective for new plants.