Rhododendron Alpine (Jinggang, Xia Hong)

Rhododendronhybrids, an evergreen shrub of Ericaceae, originated in the alpine forests of central and western China, and was introduced, cultivated and domesticated by Germany, Belgium and other countries, and bred many excellent varieties. Rich in colors, including red, pink, purple, yellow, white and so on. The patterns are mainly funnel-shaped, bell-shaped, tubular, radial and butterfly-shaped, and single or multiple flowers form umbels or heads, which are beautiful in tree shape and have high ornamental value. On the one hand, Rhododendron alpina is deeply loved by people because of its huge umbel, bright colors, beautiful flower posture and beautiful plant shape, and has become a recognized high-grade potted flower. At the same time, it has strong adaptability, no deciduous leaves, evergreen seasons and no special facilities for cultivation, so it is not only a popular annual flower, but also an excellent variety for urban and rural greening and beautification.

Most alpine rhododendrons grow in alpine areas above 1000 meters above sea level, and like cool, humid and semi-shaded environments. Strong cold tolerance, drought tolerance, fear of heat and dry air. Like scattered light, avoid high temperature and strong light. I like loose and fertile mountain humus soil and avoid hardening, stagnant water and saline-alkali environment. The flowering period is April-May, and the fruit maturity is 8-65438+1October.

First, the feeding method

1. Generally, after the fruit turns red from July to August every year, excellent mother trees are selected for collection. It is best to sow in autumn, and the seeds in spring must be layered first. Screening peat soil and 1/5 river sand should be used when sowing. Acidify the sowing substrate before sowing, and adjust the pH value to 5 ~ 5.5 with ferrous sulfate. It is usually mixed with clean fine sand for sowing. After sowing, it is covered with fine peat soil disinfected by carbendazim or bacteria and insects, with a thickness of 2 cm. After covering the soil, it should be slightly suppressed, so that the seeds can be closely combined with the substrate and the seeds can fully absorb water and germinate. The pot sowing must be covered with glass, and the bamboo bow should be erected during the border sowing, and the plastic film should be covered with moisture to prevent the fine seeds from scattering when it rains. The optimum temperature for seed germination is 15 ~ 25℃. When the substrate is dry, it should be sprayed with a fine-hole sprayer in time and germinated about 30 days after sowing. After emergence, it is necessary to strictly shade, control weeds, and prevent seedlings from being brought when pulling weeds. Gradually strengthen fertilizer and water management during the seedling growth period. The root system of 1 year-old seedlings is developed. When there are 5 ~ 6 leaflets, they can be transplanted in the next spring, and it usually takes about 8 years to blossom.

2. Cutting propagation and cutting should be carried out in May-June. Cuttings should be semi-lignified, elastic shoots, 5-8 cm long, with 2-3 leaves at the top and complete terminal buds. The cutting substrate is made of peat soil, perlite and vermiculite in a ratio of 4: 2: 2. Plug seedlings are used in industrial production, which can promote root extension and grow neatly. When cutting, you should pick and insert at the same time. It is best to dip the base with solutions such as indolebutyric acid or rooting powder, and the depth of insertion is about 2 ~ 3 cm. Water 1 time in time after cutting. The soil temperature for cuttage rooting is usually 24℃. Generally, the shading degree is higher within 15 days after cutting. After 15 days, shading can be gradually reduced, light can be gradually increased, photosynthesis can be promoted, and roots can be extended early. In general, the roots begin to elongate after 20 days of summer planting, take root after 40-50 days, and start to grow new buds after 60 days. It can be transplanted in August-September of the current year or April-May of the following year. Cutting seedlings can bloom in 2 ~ 3 years.

3. Using flower bud, hypocotyl and hypocotyl as explants for tissue culture, regenerated plants can be obtained. Generally, shoot tips or tender stems with lateral buds are used as explants, so that a large number of clustered buds can be obtained directly, and then small plants can be obtained. The induction medium was1/4 ms+ZT 2.0 mg/L+IAA 0.5 mg/L. After 25 ~ 30 days of culture, the clustered buds could be divided into 1 ~ 2 cm pieces and inoculated in1/4 ms+ZT 0.5 ~/kloc-0. In the rooting stage, in order to make the rooting seedlings grow healthily and adapt to the field environment as soon as possible, the light intensity should be increased appropriately, generally controlled at 3000~5000Lx. When buds with a thickness of 2 ~ 3 cm are formed on the subculture medium, the ramets can be cut into the rooting medium of 1/2MS+ 20g/L sucrose +2g/L activated carbon +0.5mg/L IBA for culture. After 20 days, when 4-5 adventitious roots are induced at the base of the seedlings, and the root length is about 2 cm, the culture bottle is moved to room temperature for 3 days, the film of the culture bottle is opened, and the seedlings are tempered for 3-4 days at room temperature and under scattered light, then the culture seedlings are taken out of the culture bottle, the culture medium attached to the roots is washed, and transplanted to a sterilized substrate orifice plate (1 perlite+1 mud) When the seedling height is 6 ~ 8 cm, the leaves are 6 ~ 8 pairs, and the main stem is 0.2 ~ 0.3 cm thick, the plug seedling can be transplanted into the pot.

Second, cultivation management.

1. The optimum growth temperature of Rhododendron alpine is 15 ~ 25℃, and it can withstand the low temperature of -26℃ in winter, but it should be controlled above 10℃ as far as possible, especially for seedlings. When the temperature reaches above 38℃ in summer, measures such as shading, cooling and ventilation should be taken in time. The temperature is preferably controlled within 30℃. When the temperature exceeds 35℃, Rhododendron alpine will be damaged to varying degrees, which is not conducive to flower bud differentiation.

2. Rhododendrons like semi-shading. The bigger the leaves, the more shade they need. Generally, shading nets with shading rate of 20% ~ 30% are used in spring and autumn, and shading nets with shading rate of 70% are used in summer to achieve the purpose of cooling and humidifying, thus maintaining the growth of rhododendrons in the mountains all year round.

3. Potting Rhododendron alpine with water requires that the soil in the pot should always be moist and the air relative humidity should be high. Water should be slightly acidic, so it should be acidified before watering. The method is to add a small amount of vinegar or ferrous sulfate to water, and adjust the water to weak acidity before use. Water less in winter, don't water, and keep the air moist. Water every morning in summer to keep the surrounding environment moist and spray water on the leaves. Proper watering should be controlled during the flowering period of plants to avoid falling flowers because the soil is too wet. Water accumulation in basin soil should be prevented in rainy season, otherwise it will easily lead to root rot and death.

4. The soil likes loose and fertile alpine humus soil, and avoid hardening, stagnant water and saline-alkali land. Potting can be done with humus soil under alpine deciduous broad-leaved forest, or with decomposed organic matter: vermiculite: peat soil = 2: 2: 1. After mixing the substrates, adjust the pH value to about 5.0 ~ 6.5 with 1% ferrous sulfate solution, and add rhododendron mycorrhizal fungi to the prepared basic substrate. Loosening soil 1 time per month in the growing season to prevent the normal growth of plants from being affected by matrix hardening and poor ventilation. Flowering plants should turn over the pots and change the soil 1 time a year, and the time can be arranged in the short dormancy period after flowering in spring. If you don't change pots, you should pick the residual flowers of flowering plants in time and add a proper amount of fresh and fertile acidic humus soil.

5. Fertilization should be based on thin fertilizer and diligent application, and it is not suitable to apply large fertilizer, thick fertilizer and raw fertilizer except adding appropriate amount of base fertilizer in the basin soil. During the growing season, 1 diluted decomposed cake fertilizer can be poured every month, and 0. 1% potassium dihydrogen phosphate can be added. When the buds of plants gradually expand, 0. 1 ~ 2 times of 0. 1% ~ 0.2% potassium dihydrogen phosphate solution can be sprayed to promote the huge buds, bright colors and lasting flowering. Pick the residual flowers in time after the flowers wither, so as not to consume unnecessary nutrition. When the temperature is higher than 30℃ and lower than 15℃, topdressing should be stopped. If plants suffer from physiological diseases of leaf yellowing, alum fertilizer can be used to water instead of liquid fertilizer, or ferrous sulfate or 0.2% ferrous sulfate water can be sprayed, but the effect is not as good as alum fertilizer water. [Jishan Huayao]

6. After plastic pruning, it is necessary to combine changing pots and cut off dense branches, residual branches, dead branches, horizontal branches, slender branches, long branches and diseased branches. In the growing period, the unnecessary branchlets on the branches should be thinned out. When pruning, be careful not to cut off the branches that need to be kept short, because the leaves of Rhododendron alpina are mostly clustered at the top of the branches. After flowering, new branches are produced, a new cluster of leaves grows, the old leaves fall off immediately, and then the terminal buds begin to differentiate into flower buds. Therefore, it is very important to leave tough and strong branches, which is related to the number of flowers in the next year. After the new branches germinate, they can be pruned and bundled, so that they gradually become umbrella-shaped, tower-shaped or other ornamental plant shapes.

Third, flowering regulation

European alpine rhododendron varieties

Rhododendron alpine is generally pregnant in July and August, and the bud development time is longer. After entering the greenhouse in winter, the buds are still developing. At this time, it is easy to control the flowering period of New Year's Day and Spring Festival by controlling the temperature. If the greenhouse temperature is maintained at 15 ~ 20℃, it will take about 20 days to bloom. Delaying flowering, the temperature can be kept at 5 ~ 10℃, and the temperature can be increased before flowering.