Grafting is an ancient method of propagating cuttings from trees that don't grow true to form from seed by attaching them to another tree that will provide the new tree with a suitable root system. Grafting can be done in a variety of ways. Sometimes the top of one tree is replaced with another tree, as is often done in the case of very young trees. In other situations, branches are grafted onto an existing tree and encouraged to grow as a new branch on the existing tree.
Trees graft most readily when they are closely related. Grafting to a plum allows a lot of variety because so many stone fruits are close family members. Graft cherries, peaches, nectarines, apricots or wild stone fruits onto plums. Sometimes unrelated fruits can be successfully grafted, such as a pear to an apple, but the graft is incompatible with the host and will eventually die.
Plums take best with a T-budded graft onto a tree no more than an inch in diameter. The best time to graft using this method is between mid-July and September. Make a T-shaped cut on a smooth spot on the tree, about 6 inches from the ground. Insert your previously cut graft into the T-shaped cut and slide it down about 1/2 an inch so that the bark of the host tree catches the graft and holds it in place. Wrap all the surfaces with budding tape being careful to leave the bud exposed.
About 10 days after the graft was performed, cut the tape off of the tree. Prick the base of the graft. If it is still green, the graft was successful. Paint the graft with some bright paint so that you can locate it the following spring. At that time, when the bud finally breaks dormancy, cut the top growth off the bud at an angle to encourage new growth. Cut off any undesired growth and keep new buds from crowding the graft.