Shield budding, also known as T-budding, is a technique of grafting to change varieties of fruit trees. Typically used in fruit tree propagation, it can also be used for many other kinds of nursery stock. An extremely sharp knife is necessary; specialty budding knives are on the market. A budding knife is a small knife with a type of spatula at the other end of the handle. The rootstock or stock plant may be cut off above the bud at budding, or one may wait until it is certain that the bud is growing.
Fruit tree budding is done when the bark "slips," i.e. the cambium is moist and actively growing. Rootstocks are young trees, either seedlings as Mazzard cherries for many cherry varieties, or clonal rootstocks (usually propagated by layering) when one wants highly consistent plants with well defined characteristics. The popular Malling-Merton series of rootstocks for apples was developed in England, and are used today for the majority of the commercial apple orchard trees.