Japanese maples can be propagated in a number of ways. In some cases, they will grow well from seeds. In other cases, cuttings can be rooted and grown. However, a very reliable way of propagating Japanese maples trees is through air layering. Air layering is a technique that encourages the growth of roots from the branch of a healthy living tree which is subsequently cut off the tree and planted.
Place a handful of sphagnum moss in water about an hour before you will need it.
Select a branch from your Japanese maple at least the thickness of a pencil. Thinner branches may not root properly.
Make two circular cuts through the bark that extend completely around the branch.
Make a single cut that joins the two circular cuts. Peel the bark away until you see bare wood.
Squeeze the excess water out of the moss. It needs to be wet, but should not drip water.
Wrap the sphagnum moss around the tree wound. Make sure the wound is completely covered.
Wrap the plastic around the sphagnum moss. Fold the long edge that goes in the same direction of the branch over to form a solid seal and tape it thoroughly with duct tape to complete the seal.
Seal the ends of the plastic around the ball of sphagnum moss at both ends by duct taping the plastic to the tree branch.
Wait until you see roots on all sides of the moss. The roots are formed to the point that the branch should be cut from the tree.
Cut the branch just below the plastic covered root ball, using a sharp saw or pruning shears.
Carefully remove the plastic from the new root ball. Try to disturb the roots and moss as little as possible.
Plant the newly rooted tree in a pot with potting soil. Water the tree thoroughly, but make sure there are holes in the bottom of the pot where the water can drain.
Cover the entire plant and pot with plastic, leaving only the holes in the bottom exposed. Seal the top and sides of the plastic with duct tape to keep the moisture inside the enclosure. You are making a miniature green house.
Wait a week or two until the roots are strong enough to sustain the tree. Begin hardening off the tree to the ambient moisture by making a slit in the plastic every day for five days. After five days, you can remove the plastic and continue growing the tree in the pot. After three or four weeks, your tree should be strong enough to plant in its final location.