Grafting involves taking one type of tree and getting it to grow on the roots of another. Nurseries use this method to combine hardy root stocks with not-so hardy fruit trees or scions. Sometimes the root stock is cut away, leaving only the new to grow as the primary tree, and other times, combinations of grafts are made to form a multifruited tree.
Determine whether the types of trees you wish to graft together are compatible. Fruit trees within the same species are compatible. Trees within the same genus but not the same species have a less chance of being compatible, while trees of different genera are not compatible usually, according to an article by Todd Weinmann, Extension Horticulturist at North Dakota State University.
Choose a healthy branch on the root stock tree that is at least 3 inches wide and make a straight cut with a fine-toothed saw. The cut needs to be perpendicular to the branch. Be careful not to rip the bark but to saw through it cleanly.
Cut through the bark on the sides of the branch where you want to graft new wood. The cuts should be about 3 inches long and run parallel with the branch. You can graft two or three scions (new wood) on each branch.
Cut a pencil thin branch from the scion tree. It should be 6 to 8 inches long and have two or three healthy buds. Cut the top of about a 1/4 inch above the last bud. Carefully slice a wedge that cuts across the bottom of the branch from 1.5 inches down to the bottom, from one side to the other. You will see the layers of bark and wood exposed.
Wiggle the wedged end of the scion stick into the area between the branch and the outer bark at the site of the cut you made earlier. Wiggle it down until the top of the wedge is level with the top of he branch. Do the same thing with each cut.
Wrap electrical tape or flagging around the branch tightly to hold the grafts in place. This kind of tape will stretch as the tree grows and will not girdle the tree. Apply some wound dressing to the cut surfaces to prevent insects and diseases from entering the tree.
Prune off extra grafts if more than one takes and you want to train the graft to be the main stem.