What are the propagation methods for rhododendrons? A full breakdown of common propagation methods
The rhododendron is what we know as yingshanhong or shan-shiliu, a flower whose color comes very close to blood red, and it is also the city flower of Changsha. In the past, rhododendrons often appeared in the wild hills; now they are commonly seen in parks, courtyards and other landscaping settings. They can of course also be grown in pots at home, so what propagation methods for rhododendrons are there?
1. Seed propagation
The vast majority of rhododendrons can set seed that can be collected; only double-flowered ones do not set seed. Generally the seeds mature from October to January each year. When the capsule skin turns from green to yellow and then to brown, the top of the capsule splits open and the seeds begin to scatter, so they must be collected at any time. Collect all the unopened ones that have turned brown as well, spread them in a well-ventilated spot indoors to cool, let them split open naturally, then remove the capsule shells and other impurities, put them in paper or cloth bags, and store them in a cool, ventilated place.
If greenhouse conditions are available, sowing fresh right after collection gives a high germination rate. The usual sowing time is March to April, using pot sowing, because the seeds are small. Wash the pots inside and out, dry them in the sun, sterilize them, and sterilize the soil as well. When filling the pots, use an acidic soil with good permeability, moist and fertile, rich in organic matter. To make the seedlings come up evenly, mix the seeds with some fine soil and scatter them into the pot, then cover with a thin layer of fine soil. Water by the soaking method so the water seeps into the pot, place the pot on the front windowsill, and cover with a layer of glass or plastic film in order to raise the temperature inside the pot.
2. Grafting propagation
Approach grafting: approach grafting is rather troublesome, and after it takes the shape is not very attractive, so it is not well suited to large-scale production. In the growing season, choose a good scion and rootstock for approach grafting, and at an appropriate spot, smooth and free of nodes, make one cut on each, with the cut surface 3-4cm long, reaching down to the xylem. Align the cambium of the two, tie tightly with plastic bags, and after 4-5 months the wound heals; then cut off the scion to separate it from the mother plant, and cut off the rootstock above the graft point, so it becomes an independent plant. This method is reliable for survival, quickly forms a tree, and gives quick results. If it fails, there is little loss to the plants.
Softwood cleft grafting: cleft grafting is mostly carried out in May to June, when the plants grow vigorously, there is plenty of scion material, the shoots are moderately old and tender, healing is fast, and the survival rate is as high as over 90%. For the rootstock, choose R. mucronatum (mao juan) that has been grown from cuttings for 2 years with no forking. For the scion, choose one with high ornamental value, free of pests and diseases, 3cm long, keeping 3-4 fine leaves at the top and removing all the lower leaves, and cut it into a wedge 0.5-1cm long. Cut off the new shoot of the rootstock at 2-3cm from its base, make a vertical cleft down the middle, slightly deeper than the scion's cut surface. Insert the scion so that the cambium on one or both sides matches. Tie tightly with plastic bags, put a plastic bag over the scion and the graft union, tie a transparent bag below the union to prevent rain from getting in, and maintain temperature. Normally keep the temperature inside the bag, prevent direct sunlight, give a little fertilizer and water, promptly cut off sprouts from the rootstock, and after 2 months, once it has taken, remove the bag.
Softwood side grafting: side grafting is done from mid-May to late May, still using R. mucronatum (mao juan) as the rootstock. Make a slanting cut at 6-7cm from the base down to the xylem, 0.5-1cm long. The requirements for the scion are the same as for cleft grafting, but the front is cut long on one side and short on the other; insert the long side facing inward and the short side facing outward, cover and make the cut well, align the cambium, tie well and put on a bag, and place in a shaded spot.
3. Cutting propagation
The cutting method is the most commonly used propagation method for rhododendrons. Apart from a very few that cannot root, all can survive from cuttings; they are easy to collect, simple to handle, and can preserve the fine characteristics of the variety. Cuttings can be taken throughout the year, with the best time being May to June, followed by August to September. But because varieties differ, the times vary: for Western azaleas, late May to early June; for R. mucronatum (mao juan), early June; for Eastern azaleas and summer azaleas, mid to late June.
Selection of cuttings: choose cuttings that are robust in growth, free of pests and diseases, new shoots of the current year, semi-mature branches that have become woody; terminal shoots on the outer part of the canopy are best. In principle, if the mother plant has 3 new shoots, take 1 as a cutting; if it has 5, take 2 as cuttings. The lengths are respectively: Western azaleas 5-7cm, Eastern azaleas and summer azaleas 6-8cm, R. mucronatum (mao juan) 8-10cm. For overly long branches, the tip can be cut off, the lower leaves removed, and 4-5 small leaves kept at the top; take and insert them right away.
Pot cutting method: wash and sterilize the pot, fill it with potting soil, put coarse-grained soil in the bottom 1/3 as a base layer; fill 2/3 with fine soil, make holes, insert the cuttings to 1/2-1/3 of their length, with 3cm spacing, and water with a fine-rose watering can by the soaking method.
Ground cutting method: surround the sides with bricks to a height of 15-20cm and a width of 80-100cm, fill inside with coarse-grained soil and fine soil, the method being the same as for pot cutting.