Figure 1. Chip Budding is widely used in propagating woody ornamentals and fruit trees. The bud piece is cut as shown here and covered completely with poly tape. Sometimes the bud is not completely covered (Kester, et al, 2002).

Preparation of the Bud Scion Chip

Holding the budstick, make the first horizontal cut below the scion bud about 1/4 to 1/2 inch (6 to 12 millimeters) down into the wood beneath the bud at an angle of 30° to a depth of inch (3 millimeters) deep (Figure 1, C). Start the second cut about 1/2 to 1 inch (12 to 25 millimeters) above the scion bud, cutting shallowly inwards and downward behind the bud (Figure 1, D) until it intersects the first cut, thus releasing a bud chip (Figure 1, D). The propagator can reverse the order of these scion bud cuts.

Cut surfaces will dry very rapidly, especially on the scion chip bud. If the cut surface of the scion bud dries, the survival of the scion will be low. Try to have the chip bud placed on the rootstock within five to 10 seconds from the time you started to make the first cuts. Very few beginning propagators work this quickly while achieving smooth cuts. An alternative that works very well is to cut the scion bud first and immediately place it cut-side down on your tongue. Store it in your mouth while preparing the rootstock cuts. A scion bud can remain viable for hours in a propagator’s mouth. Saliva is harmless to the bud and the plant’s sap is harmless to the propagator unless a toxic pesticide has recently been applied to the plant. It might be possible to lay the precut scion bud on a damp sponge rather than placing it on the tongue. Dehydration of the cut curfaces can also be prevented by budding in a cool shaded area, early or late in the day and on a cloudy, humid day.

Remove the wood chip from the rootstock and replace it with the block-like chip with a scion bud from the budstick (Figure 1, B, D and E). Hold the chip bud carefully between your thumb and forefinger. Do not touch the cut surfaces! The bark on the rootstock is generally thicker than that of the scionwood; therefore, the chip removed for the rootstock is slightly larger than the chip removed from the scion. The cambium layers of the bud piece must be placed to coincide with that of the stock, preferably on both sides of the stem, but at least on one side.

Note: Placing the bud to one side in order to match the cambium of the stock defeats the concept of healing and completing the cylinder of cambium. Take the extra time to match the stock and scion by cutting the chip-like cuts on the stock shallower or deeper. Firmly wrap the chip bud to seal the cut edges and to hold the bud piece tightly in place. This also enhances cambial contact since there are no protective flaps of bark to prevent the bud piece from drying out as with T-budding. Polyethylene film (poly tape) or precut poly strips from plastic bags works well for this and are superior to rubber strips, parafilm, budding bands, and patches. Most propagators prefer to use white or transparent plastic tapes. Poly tape that is 1/2-inch (12 millimeters) wide, two-mill (.002 gauge) in thickness and approximately 6 to 8 inches (15 to 20 centimeters) is used to wrap the graft union. One can also improve bud takes by covering the scion bud with this poly tape. Be sure to immediately wrap all cut surfaces to prevent desiccation.

Caution: When using rapidly growing rootstocks, degradable budding bands (rubbers) that do not cover the actual bud works best. Parafilm can be placed over the budding band and bud for added protection. The poly wrap should be quite firm, stretching the tape almost to the point of breaking. The pressure or tautness of the tying strips must be snug enough to prevent the formation of large pads of undifferentiated rootstock callus (parenchyma cells), between the scion bud (bark) and the rootstock’s wood (xylem), which will hold the scion in place but does not form a successful union with the xylem and pholem vascular tissues. Always wrap from the bottom of the bud to the top so that each layer sheds rainwater from the layer below it like a shingle roof. Cover the bud completely but do not leave any of the bases of the petiole (a leaf stem) attached below the bud eye (leaf scar) uncovered. If exposed, these petioles will quickly rot and decay and may spread to the scion bud. Properly wrapping the chip bud is the most essential step in this technique to obtain success. It may prove inadvisable to wrap or tie over the actual bud of some species, i.e., cherries, walnuts and pecan, particularly when the bud is very large and prominent. Do not cover buds with grafting wax. Thinly stretched parifilm can be used as a covering over the bud of the chip, providing it is only one to two layers thick and stretched. Parafilm permits a young, healthy bud to emerge through the film.

Care of the Chip Budded Plants

Buds that are forced into growth in late summer do not have sufficient time to harden off before winter and are subject to damage by winter cold (Z5). The only thing to do is loosen the ties (later summer or fall) as the stem grows in girth (diameter) during September and October. In the spring of the next growing season, remove the top of the stock plant about 1 inch (25 millimeters) above the inserted bud (often referred to as a bud union). Although budding bands and polyethylene tape are reported to decompose and generally do not need to be removed when T-budding, studies have shown that they must be removed when chip budding because binding or girdling of fast-growing stock plants may occur within one month. When the newly inserted bud begins to grow after forcing, some pruning and training may be necessary, especially on field grown plants. This will allow a stronger union to develop; otherwise, strong winds may cause the new vegetative growth to break off at the bud union. Vigorous new scion growth may need to be staked for proper training and upright growth.

Remove any new growth arising from below the bud union on the rootstock at the point of origin. This type of new sucker or water sprout growth may in time overgrow and dominate the grafted scion bud’s growth, resulting in stunting or even loss of the desired cultivar. A successful propagator needs to know how to perform the specialized techniques of budding and grafting woody plants as well as the proper timing of such operations. However, even more important is the horticultural care given to the stock and rootstock plants one year prior through one year after performing the propagation technique (i.e., proper irrigation, fertilization, weed control and plant training and pruning). Rootstock plants grown under proper irrigation (normal rates) will bud easier, the bud union will heal more completely and these scion buds will force more successfully into new growth than plants grown under drought conditions. Use stakes to ensure that the growth from the scion buds will be straight upright growth. Straight stems/trunks are essential to the growth of high quality budded stock. To ensure top quality budded plants; it is essential to remove unwanted sprouts from below the bus union on the rootstock. To grow high quality budded plants one also needs to consider proper fertilization and weed control.

A propagator new to this technique should start on a small scale until they become familiar with what to expect, how the buds grow, how fast the shoot growth develops, and the time that is needed to properly train the new budded plants.

Budding/Grafting Supplies

Parafilm M^TM, Laboratory Film, American National Can, Neehah, WI 54956

Grafting knives, tools and supplies, A. M. Leonard Co., 241 Fox Drive, Piqua, OH 45356, 1-800-543-8955, Web: www.amleo.com, E-mail: custserv@amleo.com

Budding Supplies, Wilson Irrigation and Orchard Supply, 1104 E. Mead, Wilson, Yakima, WA 98903, Tel.: 800/232-1174 or (509) 453-9983,
Web: www.wilsonirr.com, E-mail: roger@wilsonirr.com

Chip Budding Tape, Raintree Nursery, 391 Butts Road, Morton, WA 98356, Tel.: 360-496-6400, Web: www.raintreenursery.com, E-mail: info@raintreenursery.com

References

Reference to commercial products or trade names is made with the understanding that no endorsement by University of Nebraska-Lincoln Extension is implied and no discrimination is intended of those not mentioned.