A Detailed Guide to Rhododendron Propagation Methods, Master the Latest Techniques
Rhododendrons can be propagated by five methods: cuttings, grafting, layering, division, and seed sowing. Among these, the cutting method is the most common and produces the largest number of plants. Layering produces rooted plants the fastest, while grafting is the most complex propagation method, and is used only for varieties that are difficult to root from cuttings; sowing is mainly used for breeding new varieties.
Sowing Method
For sowing, evergreen rhododendrons are best sown immediately after the seeds are collected, while deciduous rhododendrons can have their seeds stored until spring sowing the following year. At a temperature of 15-20°C, seedlings emerge in about 20 days.
Cutting Method
When propagating by cuttings, a new shallow clay pot with a diameter of 20 cm is best, as it has good air permeability and makes rooting easier. A growing medium made by mixing 20% humus-rich garden soil, 40% horse manure crumbs, and 40% river sand can be used as the substrate. The best times for cuttings are spring (May) and autumn (October), when the temperature is between 20-25°C, which is most suitable for rooting cuttings. When taking cuttings, choose a vigorously growing, semi-lignified shoot of the current year as the cutting material, and use very sharp pruning shears; cut a 6-10 cm section with a node, and the cut should be smooth and neat. Remove the lower leaves, keeping only 3-4 small leaves at the tip. Buy 1 ampoule of vitamin B12 injection; after opening it, dip the cutting briefly in the liquid, take it out and let it dry for a moment before inserting it. Before inserting, the growing medium in the pot should be sprayed moist with a watering can the day before, but not too much, so that by the next day it is just moist, which is most suitable for cuttings. The insertion depth is 3-4 cm. When inserting, first poke a hole in the soil with a chopstick, then insert the cutting, press the soil firm with your hand so that the potting soil makes full contact with the cutting, and then water thoroughly once. After inserting, it is best to cover the pot with a plastic bag and tie the opening securely with a string; open it when watering is needed, and tie it again after watering. The pot with the cuttings should be placed in a spot without direct sunlight. The soil in the cutting pot should be sprayed with water every day for 10 days; except on rainy days, spray once on cloudy days, and twice when the climate is dry, but the amount of water sprayed each day should not be too much. After 10 days, still pay frequent attention to keeping the soil moist. Shade should be provided for 4-5 weeks, and only after sprouting can the plants gradually be given some sunlight. Rooting generally takes about 2 months. After that, shade is only needed for 2-3 hours at noon, and the rest of the time they can be exposed to light, which helps them manufacture nutrients on their own through photosynthesis.
Grafting Method
Belgian Indian azaleas are often propagated by grafting, usually by cleft grafting of young shoots. The grafting time is not restricted, and two-year-old Rhododendron mucronatum is often used as the rootstock; the survival rate reaches more than 90%.