Take cuttings from the soft, fleshy tips of healthy limbs in May or June. Select small tips no larger than a finger in diameter and make your cuttings 5 to 7 inches long, cutting them at a 90-degree angle. Strip off any leaves that occur within about 3 inches of the cut end.
Prepare a growing medium by combining equal parts of sand and peat moss. Fill nursery pots with the mixture, and then water them until water runs from the drainage holes.
Poke holes 2 to 3 inches deep in your growing medium with a pencil or a screwdriver. Leave 4 to 5 inches between holes.
Dip the ends of your cuttings in a commercial rooting hormone to facilitate rooting if you wish. Crepe myrtle often roots successfully without this aid.
Insert the cut end of each cutting into its own planting hole, pushing it down 2 to 3 inches. Keep the cutting out of cold areas and direct sun until roots form, and keep the growing medium moist. Spray your cuttings with a mist of water at least once a day or enclose the potted cuttings inside sealed plastic bags to maintain high humidity.
Transplant your rooted cuttings to a sunny area the following spring or grow them in large containers.