Cass County Extension
Grafts with similar scion and understock sizes
Whip graft, bench graft.
The whip graft works best when the stock and scion are of similar diameter, preferably between 1/4 and 1/2 inch. The stock can be either a plant growing in the field or a dormant bare root plant as in bench grafting. The stock should be smooth and straight grained. Do not graft near a point where side twigs or branches have developed.
The scion should be one-year-old wood, preferably the same size as the stock. If the stock is larger than the scion, contact can be made on only one side. The scion should never be larger than the stock. While other types of grafts depend on the bark slipping well, the whip graft does not.
Preparing the stock and scion. The cuts made in both stock and scion should match. On both parts, make a smooth sloping cut about 1 ½ to 2 inches long depending on the thickness of the material (see A and C in Figure 1). Make the first cut with a single, smooth cut with no waves or whittling. The beginner should practice by cutting extra twigs. A good quality, very sharp knife is essential .
Cutting the stock and scion. The stock may be (for a bench graft) a stem and root system of a young plant or a branch on a rootstock. Make a slanting cut about 2 inches from the butt of the young whip or leave a branch stub at least 1 foot in length. Although grafts may be made with a simple union of two slanting cuts, the strongest graft results from a whip-and-tongue system. To form the tongue hold the one-sided, slanting cut facing you, and support it with your finger. About one-third down from the tip of this cut, make a downward cut about ½ inch long as close to parallel with the grain of the wood as possible (B and D).
Fitting the stock and scion. After the cuts are made on both parts, push them together tightly enough so that the cut surfaces match as closely as possible. The cambial area (area immediately under the bark) of both pieces must be aligned for a union to develop. If the scion and stock are not the same size, match the cambiums on one side only. The lower tip of the scion should not hang over the stock. If the toe of either the stock or scion extend beyond the heel of the other, cut if off evenly.
Wrapping the graft. In most cases, it is safer and better to wrap the graft to keep it tight to prevent drying. Wrap the graft with a rubber budding strip, grafting tape, or a plastic tape such as electrical tape; then carefully cover the union and binding material with grafting compound. Start wrapping on the stock and work up onto the scion. Remove wrapping as soon as the scion has started to grow to prevent girdling of the tree.
Figure 1. The Whip Graft is usually used for grafting root stocks and scions but can also be used for grafting small branches
Grafts with small scions and large understocks
The Cleft Graft
The cleft graft is most commonly used to top work a tree; that is, to change from one variety to another. It can be used on either young or mature trees. Young trees may be cleft grafted on the trunk while older trees are grafted on branches not more than 2 ½ inches in diameter. The grafts should be within 2 to 3 feet of the trunk on main branches and preferably not more than 4 to 6 feet from ground, or the new top of tree will be too high. Branches fully exposed to sunlight and in the main stream of sap flow are more successful than those in shaded or inactive areas. Grafts on upright branches grow better than those on horizontal branches .
Preparing the stock. Branches of large trees or the trunk of a small tree, must be sawed off to provide a stock for the scions. Select a smooth, knot-free, straight-grained section. Saw the branch off at a right angle to the grain. Don't tear or split the bark. If the cut is not smooth, trim off the rough edges. The bark must be tight to form a successful graft. Using a grafting tool, or a heavy knife that may be tapped with a mallet, drive the blade into the stub to split the stock through the center so a split extends about 2 inches into the branch. In horizontal branches, the cleft should be side wise, that is, not perpendicular, to reduce breakage from birds and storms.
Preparing the scion. The scion for the cleft graft should be made from one-year-old wood about 1/4 inch in diameter. After making a sloping cut about 1/4 inch above the upper bud, cut the scion with three buds, so it can be inserted with the lowest bud just above the stock. Always note which is top and bottom of a scion stick. A scion will not grow if inserted upside down. Start below the lowest bud, and make a long, smooth cut toward the base. The cut should have a surface 1 to 1 ½ inches long. Turn the scion to the opposite side, and make a second smooth cut of the same length so one side (the side containing the lowest bud) is slightly thicker than the other side (see A and B in Figure 2). The wedge that is formed does not need a sharp point, a blunt point is preferable. If the wedge is cut to a sharp point there is danger of the bark peeling. Also a sharp scion wedge will not fit the cleft as well (C).
Inserting the scion. With a grafting chisel or a small wedge, open the crack wide enough to insert the scion easily. Insert the scion with the thicker side toward the outside (B) with the cambiums in contact. Keep in mind that the bark of the larger stock is thicker than the scion bark, so the scion should not be flush with the stock. A very slight tilt will assure a contact, at least where the cambium layers cross (D).
|Figure 2. The cleft graft is the one to use on large branches.|
The best contact point is about 1/4 inch below the shoulder of the stock. After properly positioning the scion, remove the wedge or chisel from the slit. The pressure of the stock against the scion should be greatest where the cambiums touch. When the scion is placed in the crack, the cut surface of the scion wedge should be almost entirely hidden.
Two scions are usually inserted in each slit, one at each side. This gives a better chance for getting at least one graft to grow. There is no need to tie, unless the stock is small and does not bind well. Cover the unions with grafting compound and be sure the cleft is covered its full length (E).
Caring for the graft. After the graft begins to grow, it must also be given attention. Grafts that grow vigorously may need to have the tips pinched out to stimulate branching. Very long shoots may break loose during strong winds. Cleft grafts should grow vigorously, and need only light pruning to shape their development. Never prune heavily.
After the first year, some training and branch selection may be necessary. If both scions in a cleft grow, shorten one to allow the other to develop and become dominant. Do not remove the second graft until later because it will help to cover the wound faster.
Bark graft (veneer graft)/font>
Bark grafting is similar to cleft grafting and may be performed on branches, ranging from 1 inch to several inches in diameter.
Stock preparation. The branch or trunk is cut off at a right angle in the same manner as described for cleft grafting.
The bark graft can be made only when the bark slips or
easily separates from the wood. This usually is in early spring as growth begins. Several
techniques can be used on the stock for the bark graft.
--Make a slit in the bark about 3/4 inch long
--Make two slits in the bark separated by the width of the scion.
|Stock may be prepared with a single cut (left) or a double cut.||Scion cut forming a shoulder.|
|Inserting scion for single cut (left) and double cut techniques. Note the tight fit and the nails.|
Scion preparation. The scion should be 4 to 5 inches long with two to three buds. Prepare the base of the scion by cutting inward 1 ½ to 2 inches from the base then downward, forming a shoulder and long, smooth cut. The long cut should extend about 1/3 through the twig. Keeping its base strong enough to insert but not too thick. On the side opposite the long cut, make a short cut to give the base of the scion a wedge shape for easier insertion.
Inserting the scion. A knife may be used to lift the bark at the top of the slit. Push the scion down and center it in the slit, or between both slits if the double slit method is used. Insert the scion until the shoulder rests on the stub. If the scion is large enough, one or two small nails may be used to tighten the scion to the stock. Some use electrical tape to pull the surfaces tight. If the bark does not split or tear, nailing or wrapping is not necessary.
Side graft, stub graft
The side graft is suitable for plants that are too large for a whip graft but not large enough for cleft or bark grafts. The plant or branch that will serve as the stock should be between 1 and 2 inches in diameter. The scion should be about 1/4 inch in diameter. The scion is inserted into the side of the stock, which is generally larger in diameter than the scion.
Preparing the scion. The scion should contain two to three buds and be about 3 inches long. Make a wedge at the end of the scion similar to that made for cleft grafting, but it should be shorter. Make one side slightly thicker than the other. It is not necessary to make the cuts more than 1 inch long. They must be made straight and smooth.
Preparing the understock. Select a smooth place on the branch at least a foot from the trunk. Make a downward slanting cut at a narrow angle almost to the pith (core of the branch) (see B in Figure 4).
Inserting the scion. Bend the branch slightly to open the cut. Press the scion in so the cambium layers of the stock and scion meet at one side (C). Set the scion at a slight angle to give maximum contact. When the top is released, the scion should be held in place. Tying is unnecessary if the stock binds well. Cut surfaces should then be covered with grafting compound (E). The stock should then be cut off 5 to 6 inches beyond the graft. Remove any lateral branches on the stub that might crowd the graft as it begins to grow.
Caring for the graft. In a few weeks, cut off the stock above the union (D) and cover the cut surface with grafting compound (D). If the graft has been tied, cut the binding shortly after growth starts; this will prevent girdling. In the first season, you may allow some shoot growth from below the graft, but do not permit this growth to shade the scion growth. After the first season, all growth should be cut off, except that of the graft.
Figure 4. In the side graft the cut goes across the grain to avoid splitting
Information and illustrations have been taken from Minnesota bulletin #437 and Missouri bulletins # 6971 and 6972.
|Todd Weinmann, Extension Horticulturist & Master Gardener Coordinator|
|Phone: (701) 241-5707|
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