How Do Rhododendrons Reproduce? A Detailed Guide to Common Propagation Methods
Rhododendrons can be propagated by five methods: cuttings, grafting, layering, division, and sowing, among which cuttings are the most common and produce the largest number of plants. Layering produces mature plants the fastest, grafting is the most complex, and grafting 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 as soon as the seeds are collected, while deciduous rhododendrons can also have their seeds stored until spring sowing the following year. At temperatures of 15-20°C, seedlings emerge in about 20 days.
Cutting Method
For propagation by cuttings, a new shallow clay pot with a 20 cm diameter is best, because it has good air permeability and makes rooting easy. A growing medium made by mixing 20% humus 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 vigorous current-year semi-lignified shoot tips as the cuttings, use very sharp pruning shears, and cut 6-10 cm sections with nodes; the cut should be smooth and neat, and the lower leaves should be removed, leaving only 3-4 small leaves at the top. Buy 1 ampoule of vitamin B12 injection, open it, dip the cuttings in the liquid, take them out and let them dry briefly before inserting them. Before inserting, the growing medium in the pot should be sprayed moist with a watering can the day before, but not too much; by the next day it will be 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 firmly with your hand so that the pot soil and the cutting are in full contact, and then water thoroughly once. After inserting, it is best to cover the pot with a plastic bag and tie the opening tightly with a string; open it when watering is needed, and tie it again after watering thoroughly. The pot with 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 in dry weather, 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 within 4-5 weeks, and only after sprouting can the plants gradually be given some sunlight. Rooting generally takes about 2 months. After that, shade only for 2-3 hours at noon, and the rest of the time they can receive light freely, so as to facilitate photosynthesis and produce nutrients on their own.
Grafting Method
Grafting is used more often for propagating Belgian Indian hybrids, usually by cleft grafting of softwood shoots; the grafting time is not restricted. Two-year-old Rhododendron mucronatum is often used as the rootstock, and the survival rate reaches over 90%.