1. Soil (substrate) requirements:

Suitable soil quality for Azalea planting is low salinity (EC value below 1), acidic (PH value 4.5-6.5), loose, water-retaining, breathable soil or planting medium, such as peat soil, pine needle soil, humus, sawdust, coconut bran, mushroom planting matrix, red sandy soil, sandy loam soil, mountain red soil, yellow mountain soil, gravelly mountain soil, etc., if the acidity is insufficient, it can be adjusted with an appropriate amount of ferrous sulfate. If the soil properties are not good, it needs to be improved (see Notes 7 for open field planting of Azaleas), the soil requirements for potted plants are higher, and the requirements for ground planting can be lower.

2. Temperature requirements:

The suitable temperature for Azalea growth is between 15-32°C, the temperature difference between day and night is about 10°C, and the ambient humidity is above 60%. According to the temperature and environment of the region as well as the characteristics table of Azaleas (you can download this table from this website), select suitable varieties for cultivation. Many Azaleas’ varieties with strong resistance can withstand low temperatures of -20℃ to -15℃ (natural overwintering) and can withstand high-temperature weather above 40℃. However, long-term high temperature or long-term low temperature, or the temperature difference is too small, it is not good for the growth of Azaleas.

3. Freezing damage prevention:

Provide ample light during the growing season, especially during the autumn The non-cold-resistant varieties should be pruned into a plant type close to the ground or planted in a sheltered place. The last pruning should be timely, and the non-cold-resistant varieties should be pruned early. According to the different cold tolerance of varieties, choose appropriate measures, and the methods are as follows:

a. Ground cover: Starting from the roots of Azaleas, using soil, organic matter (fertilizer), straw, leaves (bark) to pile up to above the branches can effectively protect the plants.

b. Covering a single plant: Each plant is covered with a small arched shed 20-40 cm higher than the plant, covered with a layer of 30g non-woven fabric, compacted with soil on the edge, and removed when the temperature remains above 8 °C in the next year. If it is still cold, you can put a foam film inside the non-woven fabric but pay attention to opening the holes for ventilation for a few days before removing the covering when the temperature rises in the coming year. Azaleas placed indoors can be put in a plastic bag together with the flowerpot to keep warm and moisturizing during the winter.

4. Lighting requirements:

Non-sun-resistant varieties need 50%-70% shading treatment from late spring to early autumn, and no shading at other times. Sun-resistant varieties can be left unshaded. Generally, varieties with small or dense leaves do not need shading, varieties that are resistant to low temperatures are often sun-resistant, and those grown in the open generally do not need shading. If some Rhododendron species, e.g., Deciduous Rhododendrons are shaded too much, it will have a great impact on the formation of flower buds. However, many Rhododendron/ Azaleas varieties are shade-tolerant, especially in a properly shaded environment during the flowering period, which can prolong the flowering period, so the growth state and flowering characteristics of Azaleas under sparse deciduous trees (such as maple trees) are often better than others.

5. Moisture management:

The water management of Azaleas is very important. Generally, we should pay more attention to the humidity in container cultivation, otherwise, it will affect normal physiological development. Azaleas cultivated in the open air would not be influenced a lot in this regard, unless their leaves wilt frequently. The water that is usually poured requires neutral or acidic surface water. If the groundwater is used in the north, it should be treated by salt reduction or acidification with 0.2% ferrous sulfate.

6. Fertilization management:

Before planting, 3000kg/ha of composted fertilizer or 450kg/ha of special long-acting slow-release fertilizer can be added to the substrate. Usually topdressing is mainly nitrogen fertilizer (Azaleas need ammonium nitrogen), such as 0.2% urea solution or flushing fertilization, and 0.2% urea + 0.2% potassium dihydrogen phosphate is applied 2-3 times during the flower bud differentiation period. Special fertilizers for Rhododendron/Azaleas are available for large-scale cultivation. Ground planting can reduce the number of fertilizations by 2/3 but please increase the dosage each time.

If there is yellowing of new shoots and iron deficiency, 0.1-0.2% urea + 0.2% ferrous sulfate solution can be used every 10 days or so until the new leaves recover.

7. Pruning:

Azaleas are reshaped 1-2 times a year. The first pruning in southern China is carried out after flowering. The last pruning time is appropriate in early June to early July, and it can be postponed in southern China. In addition to greenhouse cultivation in the north of the Yangtze River, it is generally only necessary to prune once after flowering and before June. Pruning too late is susceptible to frost damage and affects flower bud formation. The pruned branches and leaves should be discarded or used for other purposes and should not be left in the nursery or garden to reduce the spread of diseases and insect pests, especially flower rot disease.

Rhododendrons grown in the wild may not be trimmed, or properly trimmed. If it is a grafted flower seedling, when the anvil sprouts grow, it should be removed in time.

8. Disease and insect pest control (please refer to the column of 'pest &disease control' for details);

9. Flowering period management

To improve flowering quality, in addition to preventing botrytis (in the greenhouse) and flower rot, foliar micro-fertilizers can be sprayed 2-3 times every 7-10 days before flowering (refer to the instruction manual for specific concentrations). Do not use fertilization during the fully blooming period. In addition, during the flowering period, attention should be paid to the water supply, and wilted flowers should be removed in time. Humidity below 40% or above 90%, and temperature that is too low (below 8°C) or too high (above 30°C) are also detrimental to flowering. Proper shade can prolong the flowering period.                                          

*The above is a summary of the company's practical cultivation experience. If you have different ideas or suggestions, welcome to communicate with us！