To understand a discussion of grafting it is important to be familiar with the terms used: Bark Slippage—A condition which occurs during active cambium growth, when the bark separates very easily from the wood on a tree. This happens in Spring and early Summer after leaf-out, and usually again in late summer. Bench Grafting—Any grafting done using small, bare-root or potted rootstock which are carried to a table or workbench to be grafted (as opposed to grafting a tree growing in the ground). Bud (noun)—A piece of tissue on a twig from which leaf, shoot, and flower buds grow.
Buddy (Budding) Tape—A paraffin based tape that is stretchable and breathable. Buds can grow through it. Available at A.M. Leonard at www.amleo.com.
Bud (verb)—The act of grafting by attaching a single bud from one plant to the rootstock of another plant. Figure 1
Cambium—A two-cell-thick layer of tissue lying between the wood and bark, from which the wood and bark of a tree is derived. The cambium also transports carbohydrates between roots and leaves. For grafting to be successful the cambium layers of both scion and rootstock must grow together and form a union.
Compatibility—The condition which allows the cambium layers of different plants to grow together to form a union.
Compatibility usually requires the plants to be closely related, usually the same species.
Cultivar—A contraction of the term “cultivated variety.” It usually refers to a clone of a plant which is regularly propagated commercially, such as “Jonathan Apple.”
Dormant scion—The scion must be dormant at the time of grafting, otherwise it will die before the graft union has time to heal. The scion must also be of good quality, collected at the right season, and stored properly until time of grafting. Petiole—The stalk by which a leaf is attached to a twig.
Rootstock—Refers to the root system and lower part of the trunk of a grafted tree. Also refers to a tree which is used to attach a scion from another tree. Scion—A piece of tissue—usually a bud or twig—which is taken from one tree for the purpose of attaching it to another. Whatever grows from the scion is a genetic duplicate (a clone) of the tree from which the scion was taken.
Scionwood—A section of twig from which scions are prepared for grafting.
Top-working—The act of cutting the top off a tree and grafting on a new top for the purpose of converting the tree from one variety to another.
Union—The point at which a scion and rootstock are attached to each other. Also refers to the successful joining between the cambium layers of scion and rootstock.
A few basic principles must be kept in mind for successful grafting:
Compatibility—The cambium layers of the rootstock and scion must be able to grow together to form a long-term union. This requires they be closely related, usually the same species, i.e. apple grafted to apple, pear onto pear, cherry onto cherry, etc. Apples will not graft onto pears or cherries because they are not compatible. In some cases closely related species can be grafted, such as medlar onto pear. In other cases, such as with chestnut, the rootstock and scion must be even more closely related than just being the same species. Chestnuts often need to be grafted onto their own seedlings or siblings.
Proper season—The time of year must be correct for the species and technique being used. Proper technique—The technique must be correct for the species and the season. It must also be applied with an adequate level of skill.
Ambient conditions—The ambient conditions must be correct. Many species will heal a graft union only within a narrow range of temperatures. That range will vary from one species to another. The cambium layers of both scion and stock must have oxygen and moisture. This means oxygen must be allowed in without letting too much moisture out. A proper wrapping or coating is usually required for this.
Sharp tools—A sharp, thin-bladed knife (preferably a grafting or budding knife) should be used for grafting.