Propagation methods and soilless cultivation techniques of rhododendron

Propagation methods and soilless cultivation techniques of rhododendron

1 morphological characteristics

Azaleas are evergreen, semi-evergreen, deciduous shrubs or small trees. Most common shrubs in flower cultivation are evergreen shrubs with a height of 0.4 to 4.0 m, thin branches and very short brown or brown hairs on the twigs. Leaves alternate, ovate or lanceolate, papery or leathery, apex pointed, surface dark green, sparsely hirsute, entire. Flowers terminal or axillary, funnel-shaped or bell-shaped, often 2-6 clusters, calyx base United, bract flowers, Corolla diameter 2-6 cm, white, yellow, pink, orange, green lotus red, rose red and other flowers, stamens 5-10. Fruit a capsule, ovary 3-5-loculed, seeds minute.

2 ecological habits

Cuckoos like shady environment, avoid sun exposure, like cool and humid climate in summer, and their cold resistance varies greatly from place of origin. Rhododendron is a typical acid soil plant, which grows well in the environment with hydrogen ion concentration of 31.63-316.3 μ mol/L (pH value 4.5-5.5). However, some rhododendrons, such as rhododendron, can survive in the environment with hydrogen ion concentration of 39.81 μ mol/L (pH value 7.4). In the gardens of northern China, there are no patches of rhododendron cultivated in the open field so far, this is because the rhododendron will yellowing leaves and eventually fall off and die due to lack of iron (Fe2+) and manganese (Mn2+) in alkaline environment. The mechanism of leaf chlorosis caused by alkaline environment is not clear up to now. However, in horticultural cultivation, there are many successful examples of using complexing agents such as EDTA chelating iron to prevent and control chlorosis.

3Propagation methods

The methods of propagation include sowing, cuttage, striping, grafting, plant division and so on. Cutting and grafting can maintain the heredity of varieties and form a commercial production process. Sowing is beneficial to cross breeding and breeding excellent individual plants. Cutting with green branches, select semi-lignified branches, in the air humidity season such as plum rain season, the survival rate is high. If there are conditions, you can also use full-light spray cutting, or build a small plastic arch shed on the ground, watering with a spray can several times a day, the rooting rate is also very high.

3.1 Cuttage

The cuttings of some rhododendron varieties are not easy to take root, and sometimes even the cuttings can not take root for 2 months, and some excellent varieties of rhododendron are more prominent. Taking the rhododendron of the four seasons as a breakthrough, China has developed a high-efficiency rooting agent, which shortens the rooting time from more than 2 months to 20 days, and increases the rooting rate from 20% to 80%.

Cutting substrate is also one of the key factors affecting its survival. Rhododendron cutting requires not only rich nutrients, good ventilation and water conditions, but also clean and hygienic around the base of the cuttings. There are two ways to meet these environmental requirements. First, aerosol culture, which is the best way of training. Second, perlite culture, perlite is also a better matrix.

3.2 grafting

The grafting method can give full play to the advantages of the root system of rootstocks and the excellent characteristics of scions, and cultivate excellent individual plants. Commonly used rootstocks are imperial concubine drunken, jade butterfly, purple butterfly, generally do not use the original species of rhododendron. The scion took the tender tip of the superior variety, removed the lower leaves, left only the top 3-4 leaflets, cut the base into a wedge, and the cutting surface was 0.5-1.0 cm long.

When grafting, cut off the leaf at 2-3 cm of the new shoot of rhododendron, cut it 1 cm longitudinally, insert the scion, align the cortex, fasten it with plastic film bandage, put it into the plastic bag at the interface together with the scion, and fasten the mouth of the bag. Attention should be paid to the following when grafting. One is to avoid direct sunlight. Second, to maintain the air humidity in the scion, it is generally appropriate to see water droplets on the outside of the plastic sleeve; if not, the scion should be sprayed and re-fastened. Third, if the scion does not wilt for 7 days, the probability of successful grafting is higher. The bag was removed after 2 months, and the next spring was untied. In addition, the method of ventral grafting of twigs can be used, which is similar to that of split grafting at the top, but one plant can be grafted more than one, and it can grow rapidly after survival and can form crown width earlier.

4 soilless cultivation and management techniques

Potted evergreen rhododendron is convenient for soilless cultivation, especially some precious rhododendron treasures are more suitable for potted plants. Because of the delicate habits of rhododendron, as long as the cultivation of rhododendron is successful, the cultivation and conservation methods of other rhododendrons can be mastered. The following focuses on the soilless cultivation and management techniques of rhododendron.

4.1 Matrix

The cultivation medium of rhododendron must meet the following conditions. One is to provide an acidic environment. Pine needles, peat and sawdust all belong to acidic matrix. The second is to ensure that the roots in the substrate are not dry because of the dry weather. Pine needles or sawdust are good cultivation substrates. Because of the high air humidity, the substrates should have sufficient permeability to benefit the growth of rhododendron. In the dry areas of the north, if pine needles are used as the substrate, the roots of rhododendron will die from air drying, so it is best to choose the mixture of peat and vermiculite or perlite [1-2]. The third is to protect soil, fertilizer and ventilation. In the practice of rhododendron cultivation, it is necessary to correctly deal with the relationship among acidity, ventilation, water conservation and fertilizer conservation. For soilless culture, the concentration of hydrogen ion in the substrate should be kept between 3.16 μ mol/L and 31.63 μ mol/L (pH value 4.5-5.5) without leakage from the pelvic floor, and good ventilation should be ensured. Nutrition and water conditions can be guaranteed by watering and irrigation of nutrient solution.

4.2 nutrient solution

The nutrient solution for cultivating rhododendron should mainly meet the requirements of the following aspects. First, the pH is suitable. When the concentration of hydrogen ion in the solution is 3.16 ~ 31.63 μ mol/L (pH value 4.5 ~ 5.5), it is most beneficial to the root growth of rhododendron. The second is total nutrition. Supply all kinds of nutrients according to the growth needs of rhododendron. Although some data show that rhododendron is not tolerant to fertilizer, the proportion of various nutrients in the solution must be appropriate, otherwise it is easy to cause single salt toxicity to the plant. Third, the acid-base buffer capacity is large. Ensure that the concentration of hydrogen ions in the nutrient solution does not decrease significantly due to the addition of alkaline substances. If the water is alkaline, a rapid decrease in the concentration of hydrogen ions in the solution after watering should be avoided.

4.3 watering

The rhododendron is not tolerant to alkali, and the hydrogen ion concentration of groundwater used in cities is usually less than 100 nmol/L (pH value is higher than 7). Irrigating rhododendron with this kind of water will cause leaves to yellowing, shedding and even withering. Although the reason is not clear, some methods can be used to solve the problem, that is, set up a water tank where azaleas are planted, put the watering water in the tank for a few days, or soak in grass, tomato and orange peel. After about 7 days, the hydrogen ion concentration of the water can rise to more than 100 nmol/L (the pH value drops below 7). In order to achieve the purpose of clean cultivation, vinegar essence or edible vinegar can also be used to adjust the hydrogen ion concentration of water. About 1 tablespoon of edible vinegar is mixed with water for 500 mL. It is appropriate to prepare a small packet of hydrogen ion concentration test paper, test the hydrogen ion concentration of water after mixing with water, adjust it with vinegar if it is too alkaline, and then adjust it with water if it is too acidic.

4.4 other aspects

Cuckoos like shade, avoid exposure, like cool, avoid muggy heat, like acidity, avoid alkalinity, like thin fat, avoid big fat.