Apple trees do not grow the way most people think. You just can't grow an apple tree from apple seeds and expect to get the same kind of apples. For instance, if you plant a Granny Smith apple seed, it will not produce Granny Smith apples. To grow your desired apples, you have to "graft" them on to an existing apple tree. In fact, you can graft on several varieties of apples onto one tree and therefore, grow several types of apples on the same tree. While grafting apples might seem like it would be difficult, it can be accomplished by the average gardener with the right tools and technique.
Choose a branch (scion) from a separate tree that you want to graft onto your current tree (understock). November is generally a good time to do this. Select a branch that is approximately a half inch in diameter. Cut or clip off with a as many scions as you are planning to graft. You might want to cut a couple extra if this is your first time.
Tie the scions together and place them in a container of moist peat moss or sawdust. Wrap the whole thing with plastic wrap. Leave the scions alone in a cool, moist area until spring. A garage or basement may be an ideal location.
Prepare the understock in the spring, when the buds begin to form, but before they bloom. On the tree you are adding the scion, find a branch with a matching diameter of the scion, about a half an inch. When you cut it, leave a stub that is at least a foot long.
Cut a long, straight diagonal cut that is 1 1/2 inches long on the understock. It should start on one side of the bark and end on the other side. Do the same on the scion. They should match up when you put them together. Generally, one slice with a grafting knife should do the trick.
Make a small "tongue" on each piece. Start cutting about a half inch from the bottom and make a slit straight up about an inch. This is where the two pieces will fit together.
Put the two pieces together like a jigsaw puzzle. Tie it with electrical tape to secure the area. Do not wrap it too tightly though. Remove the tape after the scion starts to grow and bud.