Soilless Propagation Methods and Key Management Techniques for Azaleas
Propagation Methods
Azaleas can be propagated by cuttings, grafting, layering and sowing, among which cuttings and grafting are more commonly used and can maintain the excellent characteristics of the variety. The sowing method is mainly used for cross-breeding and selecting superior individual plants.
Cuttings mostly use semi-lignified branches and can be carried out from May to August. River sand, perlite plus peat are often used as the substrate. After inserting, cover the flower pot with a plastic bag and place it in a semi-shaded spot. Within 1 week, spray water once each morning and evening, and thereafter keep the potting soil moist regularly. At
20-25°C, most varieties will take root in about 40-60 days. If the cuttings are treated with rooting powder or vitamin B12, rooting can be promoted to be faster and more numerous. If propagating on a large scale by cuttings, the full-light mist propagation method can be used; this method has the advantages of fast rooting and a high survival rate.
For grafting, the Rhododendron mucronatum, which roots easily from cuttings, is usually selected as the rootstock, and a superior variety of azalea is used as the scion, using side grafting, cleft grafting or approach grafting. Varieties that are difficult to root by cuttings and grafting can only be propagated by air layering on high branches, and generally take about half a year to root.
Cultivation Management
Azaleas are mostly grown in pots, which makes soilless cultivation easy to carry out, and especially the very popular precious Western azalea treasures are even more suitable for pot cultivation. The key points of soilless cultivation of Western azaleas are introduced below.
For soilless cultivation of Western azaleas, ordinary medium-sized plastic flower pots (15-20 cm) or large imitation-antique ceramic flower pots are often chosen according to plant size. As the growing substrate, acidic substrates such as pine needles, peat, sawdust and coconut coir can be used, or a mixed substrate of peat with vermiculite or perlite (2:1) can be used. Because azalea roots are fine and slender, large-particle substrates (such as expanded clay pellets) have a smaller contact surface with the roots and strong aeration, and are prone to drying out, so expanded clay pellets, perlite and the like cannot be used alone.
The nutrient solution for cultivating Western azaleas requires strong acidity (pH 4.5-5.5), meeting the most suitable environmental acidity requirement for azalea roots. The various nutrients in the nutrient solution should be comprehensive and properly proportioned to meet the needs of azalea growth and flowering. A special azalea nutrient solution or a general nutrient solution can be used.
After planting, the first application of nutrient solution (diluted 3--5 times) should be thorough. Place in a semi-shaded spot for about half a month to let the plants recover, then enter normal management. For regular liquid feeding, feed once every 10 days, 100-150 ml each time for a medium-sized flower pot, and 200--250 ml for a large pot. For regular watering, keep the substrate moist, but never allow water to accumulate in the pot or remain in the saucer under the pot. Azaleas are not tolerant of alkaline conditions. Usually the tap water used in cities has a pH above 7, and long-term use of this kind of water for watering flowers will cause the leaves to turn yellow, fall off and even die. The simple solution is to set up a water vat where the azaleas are planted, to sun the water, and you can put some green grass, vegetable leaves, melon and fruit peels, etc. into the water; after about a week, the pH of the water can drop below 7. If you want it clean, you can use vinegar essence or edible vinegar to adjust the pH of the water, about 1 tablespoon of edible vinegar to 500 ml of water. It is best to prepare some pH test paper yourself and test the pH of the water before watering the flowers; if it is too alkaline, adjust it to a suitable level before watering.
During the entire growth process, potted azaleas need a semi-shaded environment. In spring, summer and autumn, shading is needed in all three seasons, and indoors at home strong direct light should also be avoided; in winter, some sunlight can be allowed appropriately. High temperature and stuffiness in summer often cause azalea yellowing leaves, leaf drop, and even death, so attention should be paid to ventilation and cooling and to spraying water to lower the temperature. In winter, the room temperature should preferably be around 10°C.
By adopting the soilless cultivation method above, it is believed that azaleas can be grown well whether in areas with acidic or alkaline water quality.