The Cleft Graft

The cleft graft is most commonly used to top work a tree. 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. 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.

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 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.

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). .

Watch out 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 breeze. Cleft grafts should grow vigorously, and need only light pruning to shape their development. Never prune heavily.

During the first season, let all scions and the shoot growth from below the graft grow undisturbed. However, do not permit this understock growth to shade out the scions. 

The second spring, select the most suitable scion as the permanent branch and consider the others as spares. Leave the spare scions on to assist in healing over the stub, but cut them back to a few buds on each (see B).

The third spring,severely cut back the spare scions again.

In the fourth season, or when crowding is noted, cut off all of the spare scions as seems necessary (C).

 

 

 

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The Modified Cleft Graft

Instead of trying to master the whip graft or side graft, use a simple kind of cleft graft on small understock. Stock (see B) about the same size as the scion (A) may be split and a wedge-shaped scion inserted.

Should the stock be larger than the scion, be cautious to set the scion to one side instead of on center(C). In this way the cambium of stock and scion will make contact.

Wrap this graft union (D) with a good grade of rubber tape. As the graft grows the tape stretches and eventually deteriorates.

Very large trees are generally poor subjects for cleft grafting, so when grafting their large branches, a slightly different method is ordinarily used.

Cautiously saw off the branch undercutting it first to avoid tearing the bark. You may need to recut the stub to get it smooth. Saw the branch to receive the scions, instead of splitting it.

Make two saw cuts about 4 inches deep at right angles to each other across the end of the stub, making a + shape. Then fit the scions into the four places made by these cuts.

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