Japanese maple trees can be propagated in a number of different ways. Although rooting or air layering can work, grafting to a new root stock is one of the most reliable ways to propagate Japanese maple trees. After two years, grafted tree trunks are nearly as strong as tree trunks from trees propagated using other methods.
Cut the scion (which is the part of the existing tree to be grafted) to the new root stock, in the late winter before annual growth has started. To prepare, cut the scion, making a sharp V cut so that the scion looks like a chisel. The angle of the V should be about 60 degrees.
Choose a root stock compatible with with the Japanese maple from which you have cut the scion. Many Japanese maples are Acer palmatum. Acer palmatum scions will graft well with either Acer palmatum or Acer japonicum root stocks.
Split the main growth or trunk of the root stock down the middle.
Slip the V shaped scion cut into the cut in the root stock. Make sure you have good contact between the root and the scion.
Wrap the grafted area in plastic to prevent water loss. Seal any seams in the plastic with duct tape.
Remove the plastic wrap and tape after one year.