How to grow alpine rhododendrons? A detailed guide to cultivation and management techniques
Alpine rhododendrons have very strong adaptability and can grow at normal temperatures. In Europe, they are mostly produced outdoors, and where conditions allow, greenhouses can be used for production. At different temperatures, the growth of alpine rhododendrons varies considerably.
Temperature: The optimum temperature for alpine rhododendrons is 15-20°C. At a maximum temperature of 35-39°C, growth is inhibited, and measures such as shading, cooling and ventilation should be taken promptly. The temperature is best kept within 30°C. When it exceeds 35°C, alpine rhododendrons will suffer damage to varying degrees, which is unfavorable for flower bud differentiation. Although alpine rhododendrons can generally tolerate low temperatures of -20°C, the temperature should be kept above 10°C as far as possible, especially to protect seedlings from freezing.
Light: Alpine rhododendrons prefer semi-shaded conditions. Although direct sunlight in summer is not a problem, varieties with larger leaves need more shade. Practice has shown that it is best to add a shade net in summer.
Fertilizing and watering: There are many opinions on fertilizing alpine rhododendrons. From our experience in recent years, the traditional concentrated fertilizing method used in China should be changed and replaced with "light fertilizer applied frequently," that is, balanced fertilizing with every watering, paying special attention to the formula at different growth stages. Because its influence is relatively great, every effort should be made to carefully test and analyze with each watering so as to prepare the most ideal pH and EC values. We conducted a large number of experiments at different growth stages. For example, we carried out a gradient experiment from pH 3.8 to 7.1. Although it proved that its adaptability is relatively strong, suitable acidity is the guarantee of healthy growth. We also conducted a large number of experiments from EC 1.0 to 3.8. Practice has proved that different growth and development stages have different requirements. Attention should be paid to light fertilizer applied frequently and to combining promotion with control, and the chemical composition of the water quality should be carefully tested. High salt and high calcium are unfavorable to the growth of alpine rhododendrons, so every effort should be made to use rainwater or water treated by chemical or semi-permeable membrane technology.
Breeding of tissue-cultured plantlets: In recent years, the price of finished alpine rhododendron flowers has been particularly high, and the branches are thick with few leaf buds, which is unfavorable for both cutting propagation and grafting propagation, with low survival rates and high costs. For this reason, we invited tissue culture experts from Belgium to teach the techniques. Still, due to the particularity of alpine rhododendron tissue culture, inoculation was very difficult to succeed. After 3 years of effort, alpine rhododendron tissue-cultured plantlets were finally cultivated in early 2003.