Apples grown from seed have unpredictable characteristics--they may be sweet or sour, mealy or crisp. This is why asexual (vegetative) propagation techniques are used to create new trees with the same genetic makeup as the parent. Cuttings may fail to root or have weak root systems, so apples are usually propagated by budding or grafting. Both of these techniques join two genetically different plants so that the roots of one variety support the trunk, branches and choice fruit of another.
In grafting, a shoot of the desired variety of apple, called the scion, is placed into a branch of the rooted tree, called the stock, so that the cambium layers are in contact. As the wound heals, the two cambiums start functioning as one. The scion grows and is supported by the stock as a normal branch would be. The entire trunk and branch system may be genetically scion wood if the graft occurs just above the roots.
While grafting is done during winter or early spring before the leaves unfold, budding is best done in late summer when the bark is loosely attached to the wood of the branch. A single bud is cut from the scion tree and inserted into a cut made in the branch of the stock so that the cambium layers are in contact. Again, as the wound heals the two become a single individual.
Both grafting and budding allow trees with complementary characteristics to be combined into one so that breeding for fruit quality can be done without worrying about whether or not the roots are disease resistant, cold tolerant or adapted to wet soil. It also allows a single apple variety to be combined with different rootstocks, giving dwarf, semi-dwarf trees or standard-sized trees.
One scion tree, a Golden Delicious for instance, can be reproduced much more quickly and easily using budding or grafting than would be possible with cuttings. It is also possible to graft three or four different varieties of apple on to one tree, allowing for cross-pollination without needing space for several trees and giving extended harvests.
In choosing the scion, disease resistance is just as important as taste if you want to minimize the maintenance of your tree. Consult your local extension service for recommended varieties.
When choosing a rootstock, decide whether dwarfing capability or tolerance to disease and wet soil are most important. Choose the best fit for your needs.
After grafting, the wound should be covered with a coating of sealing compound to prevent drying, the most common reason for graft failure. Budding joints are wrapped with grafting tape above and below the bud.
Any shoots that sprout below the graft or bud should be removed to allow the energy of the plant to be channeled into the scion wood.