Apple trees are grafted for a number of reasons, but mainly because seeds of fruit trees do not produce true-to-type fruit. For instance, a Macintosh seed will grow into an apple tree, but not into a Macintosh apple tree, which can only be achieved through grafting. The grafting procedure involves attaching a stem containing a few buds of a particular apple tree to a cut in another tree that has roots. The upper part is called the scion and develops into the top of the tree, while the lower part is called rootstock and forms the roots.
Select a healthy twig on the apple tree that you want to use as the scion. Make sure it is at least a year or two old with two or more buds. It should be the same size and diameter as the rootstock, or the part of the tree you want to fuse it with. The ideal time to cut the scion is in winter when the tree has gone dormant.
Use a sharp knife that has been thoroughly washed before using to kill any bacteria. Slice the twig carefully, making a straight diagonal cut. If the graft is successful, this part known as the scion, will grow to bear the leaves and apples.
Store the scion in a cool place, such as a refrigerator or a container of water to prevent it from drying up. If storing in the refrigerator, place it in a zipper bag with moist paper towels until you graft it to the rootstock, which should ideally be in spring.
Choose a branch on the host tree that has the same diameter as the scion. Select a spot on it about 6 inches above the soil line and make a similar diagonal cut, ideally in April or May. This will serve as the rootstock to provide the scion the essential nutrients it needs to grow healthy fruit.
Attach the scion to the rootstock firmly so both the cuts are aligned together. The point at which they meet is known as the union. If both pieces have the same diameter, aligning them should not be a problem. But if they have varying diameters, try to make at least one side of the cambium, or the part under the bark, of both pieces meet to form a successful union and hence a successful graft.
Wrap a piece of grafting tape or electrical tape around the union to prevent it from drying and encourage both the parts to fuse and grow as a single tree. Cover any cuts or cracks between the two pieces with grafting wax to keep nutrients in and restrict water from seeping out.