Rhododendrons are breeded mainly using cuttings. Breeding using seeds or cross-breeding are among relatively seldom used types of breeding. Rhododendron cuttings are done in a heated flowerbed of greenhouse, with constant temperature of 20 °C. As a substrate for cuttings, we use sand mixed 1:1 with peat, or just pure peat. It is possible to replace sand with perlite or grinded polystyrene. To the bottom, we can place drainage layer of gravel or sand, where height of the particular substrate should be around 20 cm.
As cuttings, we are using flexible sprouts from which we remove all but 2-3 leaves. With regard to large flowered and evergreen cultivars, thin cuttings, 6-10 cm long, without flower buds, strike better; more suitable are the cuttings without flower buds. We can cut the cuttings with short sideway cut, and the cut section can be treated by a growth stimulator. Cuttings are dug into the substrate at a slight angle, with the long cut facing down. Besides steady temperature at a breeding site, it is necessary to also maintain constant humidity, what we can achieve easier by covering using transparent plastic wrap.
Deciduous Azaleas can be cut in the spring time, as soon as the leaves of young sprouts unfurl. When making cuttings, it is essential to maintain constant humidity, since Azaleas are sensitive to it. We can cut scrubby Rhododendron forms from the second part of June to the end of August, and other large flowered Rhododendrons from September, based on ripeness of the cuttings.
In addition to Rhododendron breeding using cuttings, we can also use breeding with buds. A single plant is seeded into the ready substrate. A bud is then dug into the substrate almost perpendicularly. Enrooting ability is slightly worse, although gardener’s experience is what matters a lot here.