One of the easiest and most successful methods of propagation for ornamental trees is air layering. This simple, reliable process produces a vigorous plant in a relatively short amount of time. It's been successfully practiced for centuries, and will work well for you, too. The best time of year to air layer ornamental trees is in early spring. Depending upon the plant's variety, air layered cuttings may root by fall or take as long as two growing seasons.
Select an attractive, healthy ornamental tree to take your air layer cutting from. Look for an unblemished ½ to ¾ inch diameter branch from last year's growth. Pick a spot 12 to 18 inches from the tip of the branch to make your air layer cutting. Use a sharp, clean knife to remove any leaves from within 6 inches of either side of this spot.
Make two shallow circular cuts through the bark all the way around the branch at the layering spot. The parallel cuts should be about 1½ to 2 inches apart. Peel the ring of bark from this area and coat the exposed wound with powdered rooting hormone.
Moisten about 1 cup of sphagnum moss and squeeze the excess water out of it. Cover the wound and 1 inch of the branch on either side of it completely with the damp moss. Press it into place firmly, and bandage the air layered section with an 8-inch long sheet of plastic kitchen wrap.
Cut two rubber bands and use them to tightly bind the ends of the wrap to the branch. Cover the plastic with a piece of aluminum foil. This will reflect sunlight and keep the layer from overheating. It will also keep the sun from affecting the potency of the rooting hormone.
Remove the foil and check on the air layer's progress. You'll be able to see developing roots through the plastic wrap in as little as 2 weeks. Replace the foil and keep checking periodically. When roots begin peeking out from under the sphagnum moss, the air layered cutting is ready to pot.
Take off the foil and cut the rooted air layer from the parent plant. Make your cut about ½ inch below the rubber band. Remove the plastic wrap, but carefully keep the sphagnum moss intact around the new plant's rootball.
Plant the cutting in a pot of planting medium suitable for its species. Set it in a shady spot and keep the soil surface evenly moist. Gradually increase the amount of sunlight it receives over a period of 2 or 3 weeks until it's ready for full exposure.
Plant your ornamental tree in a permanent location and provide water and fertilizer appropriate for its variety.