Lab III. Chip Budding
Print out Chip-Budding Flash Card for concise summary of this method.
Chip budding is used in situations where T-budding might also be appropriate, especially in the nursery production of temperate fruit trees (apple, cherry), and some ornamental shade trees (honey locust, maple, etc.). The advantage of chip budding over T-budding is that the bark need not be slipping for the operation to be performed successfully, hence it can be performed slightly later in the fall budding season. Also, chip bud union formation is faster and stronger. However, with chip budding it is necessary to be more careful to get good alignment of the stock and scion cambia. For information about the use and commercial applications of Chip Budding, including links to several Web sites which describe it in detail, go to Chip Budding under the List of Grafting and Budding Methods.
B. Chip Budding Exercise Check List
1. Rootstock preparation.
- Choose a hibiscus stock plant with a stem diameter of at least 0.5 cm, but not greater than 1.0 cm at the point at which you intend to place the scion bud.
- A chip (or T-bud) should be placed at a point on the stem of the stock plant that is more or less completely lignified, as indicated by a completely formed bark (brown), rather than a terminal soft green stem.
- The chip (or T-) bud can be placed at any height up from the base, to build a multi scion scaffolded tree.
- Inserting more than two buds (Chip and/or T-) is not recommended, to minimize competition for resources and avoid prolonged bud dormancy.
2. Cutting the stock plant
- Using pruning shears or grafting knife, remove larger leaves and flowers from the portion of the shoot where you plan to place the scion.
- Before cutting, note the shape of the internode piece you will remove from the stock plant, and the complementary bud piece you will replace it with from the scion donor plant. They should be as nearly identical as possible. Note that the "vertical" and "horizontal" cuts are made at an angle - approximately 20o from the vertical in the case of the former and approx. 45o from vertical in the case of the latter. In some cases the "vertical" cut is more or less straight, as shown in the previous image, but more typically it is curved downwards.
- Make the first cut approx. 1.5 to 2.5 cm long, at an internode, by drawing the knife through the bark and into the wood, from the top downwards (approx. 20o angle). Be careful that the lower end of this cut does not extend too far inward toward the center of the stem. It should not extend inward more that about half the diameter of the stem (i.e. to the center of the stem), to avoid accidentally breaking the stem off at that point later on.
- Begin the second cut slightly (2 to 3 mm) below the bottom end of the first cut, drawing the knife downwards at an approx. 45o angle, until it intersects the bottom of the first cut. The more or less triangular piece of bark and wood can be easily removed from the stock, to create a space for the scion bud chip. Note that the bottom "shelf" of this new space is not flat, but at an approximately 45o angle, so the new scion bud is less likely to drop out before tying.
3. Cutting and inserting the scion bud
- Scion selection: In the case of temperate fruit trees, select a well developed, vegetative or mixed (apple) bud at least several nodes down from the terminal end of the branch from the scion donor tree. For fall budding of fruit trees this bud should be should be dormant but not yet defoliated. The scion buds should be from a woody section of stem, not a green, unharded, actively growing tip. In the case of tropical hibiscus, which does not require a discrete dormant bud, choose a node where there is little if any lateral shoot growth.
- For field budding of fruit trees, bud sticks with several suitable buds are collected from scion donor plants several hours earlier (preferably in the morning). Leaves are removed, retaining a 5 to 10 mm long petiole stump. This minimizes transpirational water loss from the bud stick. They are stored under cool, dark conditions, e.g. wrapped in damp burlap, and kept in an insulated container out of the sun. In the case of hibiscus, cut and insert your bud piece immediately after removing a complementary section from the stock.
- Using the same two cuts as described above for the stock, cut a bud piece out that is as nearly identical in shape and size as possible to the piece removed from the stock. If necessary, it may be slightly smaller in diameter, but not larger.
- Using the petiole stump of the scion bud as a "handle", place it into the complementary space in the stock. If properly cut, the cut surfaces should be in full contact with each other along both cuts. If the scion bud chip is the same diameter as the internode piece removed from the stock, the cambia of stock and scion should be perfectly aligned. If the bud chip is smaller than the space it will fit into, it should not be centered, but rather placed over to one side so the cambia line up on at least one side.
4. Tying the bud
- The budding rubber is wrapped tightly (pressure) around the stock and the new scion bud, from the bottom upwards, so that the edges of the budding rubber overlap like shingles on a roof. This helps avoid accumulation and entry of rain water through the cracks. Begin tying a few millimeters below the bottom of the bud. Trap the bottom end of the budding rubber beneath the first turn by holding the end at an ascending angle with the thumb and forefinger of your left hand while simultaneously stretching and wrapping the band in a counter clockwise direction, creating an "X". Continue turning, overlapping each turn by about half the diameter of the budding rubber. Go around rather than over the bud itself, or small lateral shoot in the case of hibiscus, continuing up about 1 cm above the bud. In some cases with apple and other fruit trees, if the bud is small and hard, it may be completely covered by the budding rubber.
- Terminate the wrapping about 1 cm above the top of the new bud chip by pulling out a "loop" with the right hand, tucking the end of the rubber band through this loop, and then pulling the end through, before releasing it and trapping it in place.
- Although fruit tree chip buds are not wrapped further, in the case of hibiscus, you may wish to cover the first (rubber) wrapping with a piece of Parafilm to further minimize moisture loss. Cut a piece of Parafilm about two inches wide and 3 inches long. The paper backing is divided into two inch sections, so cut it along that line. Remove the paper backing, and fold this 2 x 3 inch piece in half long ways so it measures about 1 x 3 inches. To adhere firmly, the Parafilm should be stretched slightly before it is wrapped in place. Hold one end of the Parafilm just below the bottom end of the budding rubber wrapping, and wrap upwards, just as you did with the budding rubber, until the rubber wrapping is entirely covered. Remember to stretch the Parafilm as you wrap. At the upper end, fix the Parafilm in place, so it will not unwrap, by running your thumbnail across it, to create a crease, which tends to stick it to the layer of Parafilm below.
- For large scale field budding of fruit trees, tying is often done by a second person following directly behind the budder. A team like this can do a thousand or more buds a day.
5. Post-budding management of the Chip-budded plant
- Place the budded hibiscus under shade in the greenhouse for two to three weeks, before removing the tying materials and inspecting the graft. A thin line of whitish callus along the cut edge is a good sign that the stock and scion are beginning to form a graft union. Replace the wrapping material for several more weeks.
- If you have not grafted another scion onto the terminal end of the same shoot where one or two bud grafts have been placed, shoot growth from the new bud can be encouraged by cutting back the top of the shoot to remove apical dominance. If this is not feasible, shoot growth may be delayed for many weeks, even though the graft union is completely healed.