How to propagate and cultivate azaleas by hardwood cuttings?

How to propagate and cultivate azaleas by hardwood cuttings?

Rhododendron generally refers to the genus Rhododendron of the rhododendron family, which is one of the three alpine flowers in the world and one of the top ten famous flowers in Chinese tradition. China is the origin and geographical distribution center of rhododendron in the world, with 571 original species, which have beautiful plant shape, colorful flowers, high ornamental value and broad market application prospects, so they are widely used in landscape engineering.

Cutting is the main propagation method of deciduous, semi-evergreen and evergreen rhododendron, and it is widely used, but because of the difficulty of rooting and slow growth after cutting transplanting. Therefore, in view of the high demand for rhododendron seedlings, difficult rooting and slow growth of cuttings, in recent years, scholars at home and abroad have carried out experiments on cutting seedlings of some species. It is found that cutting rooting is affected by endogenous factors such as endogenous hormones, rooting cofactors, nutrients and antioxidant enzyme activities, while exogenous auxin can regulate the physiological activities of cuttings and induce enzyme activities and auxiliary factors. Thus promote cell elongation, division, root primordium differentiation and adventitious root formation. Cutting time is closely related to the Lignification degree and physiological characteristics of cuttings, which is another key factor affecting the rooting of plant cuttings.

1. Laying of nursery bed: the nursery bed is set in glass greenhouse or plastic greenhouse, red brick or cement brick is used at the edge of the bed, one drainage hole is reserved at the bottom of the seedbed every 100cm, and then stones, pebbles and coarse sand are added successively from bottom to top to increase the drainage and ventilation of the seedbed; the cultivation substrate of thick 10~15cm is laid on the coarse sand, raked and gently pressed to level the seedbed and watered through. In order to control the temperature, humidity and light of the seedbed environment, a curved plastic shed was built on the seedbed, the shed was equipped with automatic spraying facilities, and a sunshade net was set up at the 30cm on the plastic shed; after the seedbed was made, the matrix and the surrounding environment were disinfected with 500x carbendazim aqueous solution.

2. Cuttings collection and production: the adult plants of rhododendron, which are about 5 to 25 years old and growing vigorously, are selected as the mother plant for ear harvesting, and the sturdy woody branches (also known as hard branches) in the upper canopy of the plant are collected in June. Spray water to moisturize and transport it back to the room in time. Select the sturdy and erect twigs with no disease and insect pests and no flower bud (with bud), cut and grow the cuttings of 10~25cm, the length of the hard branch is 8-10cm, retain 2-5 branches at the branch point, remove the buds at the top of the 2~3cm branch, remove the basal leaves of the cuttings, retain 3-4 upper leaves, and cut off 1-inch, 2-2 and 2-3 according to the leaf size to reduce water evaporation. On the basal side of the cuttings, the cortex and cambium with a length of 1.0 to 1.2 cm were removed with a grafting knife, and the cutting surface was more than 45 °with the branches, which was beneficial to the absorption of rooting agents and the formation of large area callus.

3. Callus treatment: 1min of cuttings was treated with IBA aqueous solution of 1000mg/L, then 1min at the base of cuttings was soaked in NAA 500mg/L aqueous solution and dried naturally for 12 hours; cuttings were placed in an environment with a temperature of 23 ℃ and a relative humidity of 60% for 6 hours, and then the cuttings were placed in an environment with a temperature of 10: 15 ℃ and a relative humidity of 40% for 2 hours. Finally, the base of the cuttings was dipped in ABT rooting agent solution (ABT rooting agent: water = 1 g: 2kg) for 3 seconds and placed in an environment of 23: 26 ℃ and relative humidity of 50: 60% for 24 hours.

4. Cutting and management: immediately after cutting treatment, a small hole was introduced with a small bamboo stick to reduce the mechanical damage of the substrate to the cutting tissue, the row spacing between cuttings was 15 × 15cm, and the cutting depth was 1 stroke, 3 trees and 1 stroke 2 of the cuttage length, and water was sprayed after cutting. During the experiment, an automatic intermittent spray system was used to replenish water and humidify: 5min/4h during the day, 2 minutes at night, 4 hours at night, and then gradually reduce the number of spraying water 40 days later; the temperature and light intensity in the shed were adjusted by ventilation and shading network on both sides of the plastic shed according to the weather conditions (the air temperature in the shed was controlled at 20. 0: 30. 0 ℃, and the relative humidity was 80. 0%. 0%) When the temperature is higher than 30. 0 ℃, open the plastic greenhouse for ventilation and reduce the temperature; in order to reduce pollution, remove the fallen leaves and rotten cuttings in the seedling bed in time, and spray alternately with 500 times carbendazim or 1000 times methyl thiophanate aqueous solution every 7 to 10 days.

After 50 days, the rooting of rhododendron was observed and checked every 10 days. When there are more than 3 roots at the bottom and the root length is above 2cm, transplanting can begin. The transplanting substrate is peat soil: yellow loam: perlite: vermiculite is 4: 1: 1: 1: 1. Pour root water thoroughly when transplanting, set up a shading net at the 50cm off the ground, the shading rate of the shading net is 50%, cover the sunshade net from 9 am to 5 pm, remove the sunshade net at other times, and remove the sunshade net after transplanting for 2 months.

Using this propagation cultivation to propagate rhododendron by cutting, the callus formation rate is as high as 95%, the rooting rate is 90%, each plant has more than 3 roots, and the root length is more than 2cm. In the second year, the growth height reached 30~50cm, the branches were strong and could come out of the nursery. The technology lies in that the Lignification branch of the previous year is selected as the cuttage, the front end of which is provided with a transitional branch from semi-Lignification to Lignification in the same year, and the cuttage is more than twice the length of the traditional cutting. after rooting, the plants with multiple branches are rooted and transplanted in the same year, and the second year can be used as a strong seedling to come out of the nursery, which solves the situation of branching only in the second year after the original cuttage has survived, and can only be used as a strong seedling nursery after the third year. And the seedlings of this technique have strong branches and the whole plant grows rapidly. [Jishan Huayao] 2. This technique breaks the traditional concept of cutting time. Cutting from June to July is beneficial to rapid rooting and rapid development of seedlings after rooting. 3. This technology solves the problems such as difficult rooting, low reproduction rate and slow production of rhododendron cuttings, and effectively improves the rooting rate and rooting quality. 4. This technique needs no special treatment and is easy to operate. it is an effective method for large-scale and rapid propagation of rhododendron, and it is especially suitable for industrial breeding of evergreen rhododendron.