Unit 7. Grafting and Budding During this laboratory you will be introduced to various methods used to graft and bud horticultural crops. A. Introduction to Grafting B. Terms and Definitions C. Basic Steps in Grafting D. General Classes of Grafting Tools E. Basic Types of Grafts F. Introduction to Budding G. Budding Methods H. Laboratory Exercise Outline I. Laboratory Questions 1
A. Introduction to Grafting Grafting entails the placing of parts from two separate plants together in such a manner that they will unite and continue to grow as one plant. The top portion of the grafted plant, or the portion that is to become the top of the grafted plant is called the scion. The lower portion is referred to as the stock or rootstock. The following section will include the definition of several terms related to the topics grafting and budding that you will need to know. B. Terms and Definitions 1. Grafting - the art and science of connecting two or more pieces of living plant tissue together in such a manner that they will unite and subsequently grow and develop as one plant. 2. Budding - a type of grafting except that the scion (see below) is reduced in size to contain only one bud. 3. Scion - the short piece of detached shoot containing several dormant buds, which, when united with the stock, comprises the upper portion of the graft and from which will grow the stem or branches, or both, of the grafted plant. It should be of the desired cultivar and free of disease. 4. Stock (rootstock, understock) - the lower portion of the graft which develops into the root system of the grafted plant. It may be a seedling, a rooted cutting, or a layered plant. If grafting is done high in a tree, as in topworking (see below), the stock may consist of the roots, trunk, and scaffold branches. 5. Interstock (intermediate stock, interstem) - a piece of stem inserted by means of two graft unions (see below) between the scion and the rootstock. An interstock is used for several reasons, such as to avoid an incompatibility (see below) between the stock and scion, to make use of a winter-hardy trunk, or to take advantage of its growth-controlling properties. 6. Graft Union - the juncture at which the scion and stock of a grafted plant have successfully united. 7. Double working - a double graft involving a rootstock, interstock, and scion whether done in one or two steps. 8. Topworking (topgrafting) - the use of various grafting and budding procedures to change the scion cultivar of usually established plants. 9. Incompatibility - the inability of a grafted scion and stock to produce a successful graft union, or to have the resulting grafted plant develop unsatisfactorily. 2
10. Vascular Cambium - a thin tissue of the plant located between the bark (phloem) and the wood (xylem). Its cells are meristematic; that is, they are capable of dividing and forming new cells. For a successful graft union it is essential that the cambium of the scion be placed in close contact with the cambium of the stock. 11. Callus - a term applied to the mass of parenchyma cells that develop from and around wounded plant tissue. It occurs at the junction of a graft union, arising from the living cells of both scion and stock. The production and interlocking of these parenchyma cells (callus) constitute one of the important steps in the healing process of a successful graft. C. Basic steps in grafting The basic steps in grafting are the appropriate selection of stock and scion and the choice of time and method of making the graft. The successful execution of the graft depends upon: 1. The proper cutting and fitting of the stock and scion pieces. 2. The proper binding and protection of the graft during the healing. 3. Appropriate attention to the graft during the healing period. D. General classes of grafting tools 1. Cutting and fitting tools - knives, blades, double blades, punch outs, machines, clefting tools, saws, clippers, etc. 2. Bindings - hammer and nails, budding rubbers, raffia, waxed string, tapes, etc. 3. Protection - polyethylene bags, grafting cases, mist chambers, waxes, etc. 3
E. Basic types of grafts Grafting may be classified according to the part of the plant (rootstock) on to which the scion is placed. This would generally be a root or various locations of the canopy (stem). There are three categories: 1. Detached scion grafts - This involves removing the scion from the root system of the donor plant and removing the shoot system of the rootstock before a successful graft union formation occurs. This includes apical, side, bark and root grafts. a. Apical grafts Whip and tongue graft Splice graft Cleft graft b. Side grafts Side Veneer graft c. Bark grafts d. Root grafts Whole-root and piece-root graft Nurse-root graft 2. Approach grafts - This involves leaving the root system of the scion and the shoot system of the rootstock in place until after a successful graft union formation occurs. 3. Repair grafts - This includes grafts used to repair established trees. F. Introduction to Budding This is a type of grafting in which the scion consists of only one bud and a small section of bark, with or without wood. Most budding methods depend on the bark of the stock "slipping" (i.e., the bark easily separates from the wood), therefore with the exception of chip budding, all bud-grafting must be done when the rootstock is actively growing. As a rule budding is a simple and highly successful method of grafting. Its use is usually confined to young plants or the smaller branches of large plants. Only vegetative "buds" are used. G. Budding Methods 1. T-budding (shield budding) - Used widely for roses, fruit trees and woody ornamentals. 2. Patch budding - Primarily used for nut trees. 3. Chip-budding - Can be used when the bark is not slipping. H. Laboratory Exercise Outline - Unit 7 Today your instructor will demonstrate the cleft, whip and side veneer grafts and "T" and chip buds. Following these demonstrations you will be provided with various examples of grafting and budding wood with which to practice making the following grafts - whip and side veneer grafts, and "T" and chip buds. Upon completion of successful practices you will have an opportunity to graft and bud your own plants. 4
I. Laboratory Questions - Unit 7 1. Why were the stock and scion pieces placed carefully together? (5 points) 2. Why are grafted parts usually tied together and given some form of drying protection? (5 points) 3. How were these points attended to in the various grafting and budding operations performed during this laboratory period? (5 points) 5