There are several methods you can use to propagate rhododendrons, but not all of them will produce a clone of the parent plant. Propagating by seed, for example, won’t give you a clone. Propagating by cuttings, grafting and layering are the methods you’ll need to use in order to clone your rhododendron. Cuttings are the easiest and usually the quickest method, however. Take cuttings in early spring, less than a month after new growth emerges, or during summer.
Cut off a stem tip at an angle using clean, sharp pruning shears or a knife. Make a cutting that is 1 to 4 inches long, depending on the size of your rhododendron, and has several leaves or leaf nodes and one flower bud.
Remove the lower leaves on the cutting, allowing no more than two or three top leaves to remain. Wound the cutting by making a 1/2- to 1-inch cut into the bark layer on either side of the stem. Dip the severed end of the cutting into rooting hormone.
Fill a small planter pot that has drainage holes in the bottom with a mixture of equal parts peat moss and sand or perlite. Insert the severed end of the cutting into the potting mixture so that it can stand erect on its own and the wounds in the stem are below the surface.
Water the cutting lightly. Place the planter pot into a clear plastic bag and tie it at the top. Place the pot away from direct sunlight.
Transplant the cutting outdoors in early spring, after it develops a root system and new growth emerges on the stem, which usually takes about six weeks. To determine whether your cutting has formed strong roots, tug gently on the cutting to feel if it resists being pulled upward.