Cutting propagation of Rhododendron is the most commonly used and simple method. As long as the female parent grows healthily, many branches can be sprouted every year for cuttings. Cuttings of 4-5 cm long can produce 4-5 flowers after 3 years of survival; the crown will be formed after 6-7 years; the grafted seedlings of the same age will be more than those of the same age after 10 years; the cuttings of 30 years old still show no signs of decline. Many hybrid Rhododendron often change branches and new varieties can be obtained by cutting. For example, amateurs in Wuxi used the "Brocade Robe" of Xijuan to cultivate four varieties, namely qingnu, Lian, fengniang and Xinhong, and obtained large flowered hat from Xiaoshan brocade. The main key points of Rhododendron cutting are as follows
Pink Rhododendron
1、 Time: cutting should be done at the end of spring and early summer, but there is a slight order due to the variety and the growth of new shoots. Generally speaking, the West cuckoo is in late May, the Rhododendron is in the first ten days of June, and the eastern cuckoo and summer cuckoo are in the middle of June. At this time, it was the plum rain season in the south of the Yangtze River, and the air was mild and humid, which was conducive to the rooting and healing of cuttings.
2、 Cuttings: after flowering of Rhododendron, the residual flowers and ovary should be removed in time. In some species, buds can be removed before flowering to promote the early emergence of new shoots. When the fine hair of the new branch is yellow, that is, it has reached the semi lignification, the robust and disease-free branches can be selected as cuttings. The cuttings should be gently broken off from the old branches, with a little of the last year's tissue (heel), and then flattened, leaving only 3-5 leaves at the top, and all the rest removed.
In northern China, semi lignified branches are usually cut in summer and autumn, and annual branches are selected as cuttings in spring, with a length of 4-12 cm and a maximum of 20 cm. The upper half of the leaves were left in the cuttings, and the lower half of the leaves were cut off. Common species can take root without any treatment. After soaking the lower part of cuttings with trace amount of sucrose for 8-12 hours, washing cuttings can promote rooting. Soaking cuttings with low concentration of IBA (10-20 μ L / L) can promote the rooting of species that are not easy to take root.
3、 Cutting: Rhododendron is acid soil flowers, loose, good exhaust mountain mud (orchid soil) into tile pots or shallow wooden boxes is good. It can also be used for cutting with washed coarse sand. The hybrid Rhododendron can take root in about one month.
Generally, vermiculite, coarse sand, surface sand mixed with water moss, rotten leaf soil, peat soil, etc. can be used as cutting soil. Large flowerpots, wooden boxes, etc. can be used as cutting beds, with large grain sand as drainage layer. After cutting, cover with plastic film or glass, keep high air humidity and shade about 50. For the cutting depth, the short cuttings are equal to 1 / 2 of the length, and the longer cuttings are equal to 1 / 3 of the length. After cutting, water should be fully watered, and then water should be sprayed frequently to keep the soil and air moist. If cuttings are carried out with plain sand, they should be potted earlier after rooting; if they are cutted with rotten leaf soil or mountain mud, they can be kept for 3-5 months or continue to grow for half a year, and then they can be planted in pots separately. The cuttings usually take shape and blossom in 3 years. The results showed that the "bottle inserting method" was very effective for the varieties such as "Xueguan" and "tiannv dance" which were difficult to survive. The method is to use a new tile pot with a diameter of 15 cm and pad the bottom with tiles. In the pot, three round sticks (or glass tubes, etc.) with a diameter of about 2 cm are erected first. Then the flowerpot is filled with sand. After watering, the round rods are pulled out, and then the holes are filled with mud. One branch is inserted into each hole and covered with a wide mouth glass bottle to maintain stable humidity.
4、 Management of cutting: put it under the shade shed. The canopy is shaded with two layers of reed shade. The air under the shed should be ventilated. When the weather is fine, the water should be poured once in the morning and evening respectively, and the roots are generally 50-60 days old. After rooting, remove a layer of reed curtain and water properly. High temperature, high air humidity and soil moisture are easy to cause root rot. In the first ten days of September, the root system of cuttings was gradually full of fibrous roots, especially for those planted in bottles. Before and after the middle of October, they should be planted in pots with a diameter of 10 cm, otherwise the fibrous roots will pass through the sand layer and the root tips will shrink easily. After the basin is put into a greenhouse, it is placed in a warm and sunny place. In winter, the room temperature should not be lower than 6-7 ℃ and should not be placed in the dark. From March to April of the next year, we can add some grass juice or other rotten fertilizer when watering, and apply thin fertilizer frequently to accelerate the growth. In the first 12 years, it is advisable to remove the flower buds, not to consume nutrients for flowering, so as to form a full crown as soon as possible.