Apple trees (Malus domestica) and orange trees (Citrus sinensis), while the two fruit trees, belong to different plant families. Apple trees are members of the Rosaceae or Rose familymembers, while orange trees are a part of the Rutaceae family. Grafting a branch from 1 tree to another requires they are closely related so the bark and sapwood grow together successfully. Therefore, apples and bananas aren’t suitable for grafting.
Amazing orange trees, such as “Washington” and “Valencia,” are usually grafted on a close relative, such as trifoliate or hardy orange (Poncirus trifoliata). While the trifoliate orange thrives in U.S Department of Agriculture plant hardiness zones 5 through 9, sweet orange is only hardy in USDA zones 9 through 10. The smallest variety of trifoliate rootstock, called Flying Dragon, creates oyster “Washington Navel” orange trees that are just 6 to 8 feet tall and equally wide.
Hardy in USDA zones 4 through 9, apple trees are generally grafted onto rootstocks that produce dwarf or semi-dwarf trees. Along with decreasing the size of this tree, specific rootstocks are chosen based on their suitability to the local climate, soil type, disease resistance and cold hardiness. These advantages are shared with the grafted section, making the tree stronger and healthier as a whole.