There are two main ways, as there are with most plants – by seed and by cuttings. Raising azaleas from seed is a lengthy business and, unless you are interested in hybridising them, worthwhile only with the few true species. Reproducing by cuttings is easy and much quicker. Take cuttings in late summer when the new wood is semi-ripe; then it can be bent over but will not snap until it’s been bent almost double. Cut lengths of healthy shoots about 2-3in long and trim away the lower leaves.
Use as a rooting medium a half-and-half mixture by volume of moss peat and lime free sharp sand. Spread the mixture in a container to which a more or less airtight translucent cover can be fitted – a flowerpot with a plastic bag tied over it will do fine.
Dip the bases of the cuttings in a hormone rooting powder, and push them gently into the rooting medium. Seal the container and stand it in a well-lit spot out of direct sunlight – a cold frame outdoors would be ideal. Don’t allow the cuttings to dry out. Most azaleas will root within about three months.
Layering also works well and is the easiest method of all. Simply select a low-growing shoot or branch and anchor it into the soil with a small wooden peg held down with stones. Remember where you made the layer, for it may take up to two years to root. When it has rooted, sever it cleanly from the parent and treat it like a mature plant.