What kind of potting soil is suitable for rhododendrons?
The choice of soil is crucial to the growth and development of rhododendrons. There are many ways to mix potting soil for cultivating rhododendrons, varying with the cultivar, but it must meet the following conditions: loose, well-drained, well-aerated, acidic soil, rich in humus, and with sufficient base fertilizer. Rhododendrons usually grow vigorously only in acidic loam; if in alkaline soil, the leaves soon turn yellow and the plant withers and dies. Rhododendrons are regarded as an indicator plant of acidic soil. Leaf mold soil is generally acidic, and pine needle humus soil is the best, making it a relatively ideal potting soil for growing rhododendrons. It can be dug from beneath pine and cypress trees in mountainous areas, or taken from soil beneath areas with many pine and cypress trees planted in courtyards. Before use, add an appropriate amount of sulfur powder and white alum to increase its acidity. Soil with a high humus content is most suitable for the growth of rhododendrons. With plenty of humus, nutrients in the soil can be replenished in time, the soil structure improved, and the soil made able to retain water, hold fertilizer, allow aeration, absorb heat and keep warm. It can also reduce the harm of toxic substances in the soil and promote the rhododendron's root system to spread in all directions.
The new products Tongguan Mountain soil from Yixing, Jiangsu, and Heishan soil from Fenghua, Zhejiang, are most suitable for the growth and development of rhododendrons and are widely used in various places. Potting soil can also be made at home. Take 2 parts of weathered surface mountain soil, 1 part fallen leaves, and 1 part dried dung of herbivorous animals, pile and mix them for 1 year, sift out impurities, and it is ready for use. Alternatively, use 3 parts mountain surface soil, 3 parts horse manure, 3 parts fallen leaves and weeds, and 1 part human feces and urine, pile them in layers to compost, and after 1-2 years sift and use. The prepared potting soil should be stored indoors to prevent reduced fertility from sun and rain.