Azaleas are slow growing and need some extra care and attention to ensure constant growth and repeated flowering. Careful attention should be given to the position, soil, shade requirements and protection from strong drying winds (of a Western Cape summer or the early spring winds in the summer rainfall areas of South Africa). The Western Cape winter wind is acceptable as it is normally moist and cold. Watering is required during winter in the summer rainfall areas.
The selected planting site should be partially shaded and it should offer protection from the midday sun. Position these plants where they will get morning sun and/or late afternoon sunlight. Planting azaleas under trees that provide light shade (Acer, Tipuana and Sambucus) would also be appropiate.
Azaleas prefer acidic soil and this is achieved through the use of matured cow manure and milled pinebark or peatgro (peat). These should be mixed in equal quantities and added to the soil used to refill the planting hole. Azaleas are not deep rooted and their planting hole must not be deeper than 45cm. The hole should be 45cm wide. Ensure that their feeding roots are just below ground level.
It is essential that azaleas have good drainage and receive adequate water during hot and/or dry weather. One good soaking a week is recommended and care must be taken that the shallow feeder roots are not exposed or damaged. It is advisable to moisten the foliage on very hot days.
This is one of the most important aspects of growing azaleas successfully. Mulch is typically an approximately 5cm thick protective layer of coarse plant material that may include compost, peatmoss, bark or pine needles that is placed on the ground around the plants stem. The advantages of mulching include the reduction of the temperature of the soil which in turn saves water due to the lowering of evaporation rates. The area mulched should correspond to the width of the plant above ground. Do not use groundcover plants as mulch. Remember to renew your mulch as it decomposes.
Azaleas are naturally slow growing and therefor are not fast feeders. These plants are slow continuous feeders and the application of a small amount of liquid seaweed emulsion (Nitrosol or Seagro) regularly through the growing season would be sufficient for their needs. Apply a solution of Chemicult or similar comprehensive fertilizer at three week intervals if the leaves yellow during the growing period until the natural green reappears.
Fungus and Insect Problems
Older plants may develop a lichen-like fungal growth on the older stems and branches. This is normally due to the plant getting too much moisture in summer combined with poor air circulation. This condition is more likely to be associated with summer rainfall regions. This fungus can be controlled by spraying with Copper Oxychloride at the rate of one tablespoon per 5l of water once every two months during the growing season.
The treatment discussed above will also control the occasional development of leaf gall which is a swelling and hardening of the new leaves. Leaf gall only occurs on certain varieties of azaleas and it is more prevalent in summer rainfall areas.
There are a few simple rules to follow if you want to grow azaleas in containers. Do not plant a small plant in a big container because these plants are slow growing and therefore do not need much space for their roots.
You should use soil that is a mixture of approximately equal parts of compost, potting soil and garden soil. Include a layer of bark or stone at the bottom of the pot to aid drainage.
Remember to add a handful of super phosphate into each container. Mix it into the soil thoroughly and water regularly with a mixture of seaweed emulsion from the beginning of September until the end of February. Apply this feeding in small regular doses and don't forget to mulch. Keep the container in a shady well ventilated position.
Trim lightly after flowering to maintain a balanced shape so that the new shape is developed while the plant is producing new growth. Try to form as large a crown as possible if you are growing them as standards so that the main stems are shaded by the well-developed crown. Keep competing side-stems pruned so that the plant does not lose its standard shape.