Cleft Grafting
Let us discuss today the Cleft Grafting or Wedge Grafting.
Introduction:
What is Cleft grafting? Cleft grafting is a grafting method which allows the union of a rootstock limb that is much larger in size than the scion piece. Cleft grafting is conducted in late winter when both the rootstock & the scion are in a dormant condition.
One of the simplest and most popular forms of grafting, Cleft grafting is a method for top working both flowering and fruiting trees in order different varieties. Cleft grafting is used to propagate varieties of camellias that are difficult to root. This type of grafting is generally done during the winter and early spring while both scion and rootstock are still dormant. Cleft grafting can be performed on the main stems or on lateral or scaffold branches. Some examples of Cleft grafting used fruit trees are apples, cherries, pears, and peaches.
The rootstock used for Cleft grafting must range from 1 to 4 inches in diameter and should be straight grained. The scion must be about 1⁄4-inch in diameter, straight, and long enough to have at least three buds. Scions that are between 6 and 8 inches long are generally the easiest to use.
Cleft Grafting tools:
The Tools used for Cleft grafting are:
Knife:
A razor-sharp knife is very essential. The knife can be as simple as a sturdy pocket knife, or a special grafting knife. Just as important is to keep steel or stone nearby to keep an edge on the blade.
Grafting wax:
This is usually a paraffin-based wax that can be softened in the palm of your hand & applied to a new graft to prevent desiccation.
Tape:
Electrical tape can be used (as long as its cut later to make sure it falls off before girdling the branch). There is a cloth-backed grafting tape that will decompose.
Budding rubbers:
Budding rubbers are elastic bands, typically 8 inches long, which do a fine job of maintaining adequate pressure.
Grafting compound:
Grafting compound is often an asphalt-based tree wound dressing that prevents moisture loss from the graft.
Pruning Saw:
It gives a nice clean cut and that the blade retracts into the handle.
Cleft Grafting steps:
The steps for cleft grafting are mainly divided into four types;
Preparing the Rootstock:
The stock must be sawed off with a clean, smooth cut perpendicular to the main axis of the stem to be grafted. Using a clefting tool wedge and a mallet, create a split or “cleft” through the center of the stock and down 2 to 3 inches. Remove the clefting tool wedge & drive the pick end of the tool into the center of the newly made cleft so that the stock can be held open while inserting the scion.
Preparing the Scion:
In Cleft grafting, one scion generally inserts at each end of the cleft, so prepare two scions for each graft. Choose scions that have three or four good buds. Using a sharp, clean grafting knife, start near the base of the lowest bud & make two opposing smooth-tapered cuts one to two inches long toward the basal end of the scion. Cut the side with the lowest bud somewhat thicker than the opposite side. Be sure the basal end of the scion regularly tapers off along both sides.
Inserting the Scion:
Include a scion on each end of the cleft, with the wider side of the wedge facing outward. The cambium of each scion must contact the cambium of the rootstock.
Waxing the cleft graft:
The cleft graft must be waxed so that all cut surfaces are covered. Cracks sometimes extend as the wax sets. Check wax after a few days & again after several weeks to ensure that all surfaces are kept covered.
Securing the Graft:
Remove the clefting device from the cleft so that the rootstock can close. Pressure from the rootstock will grip the scions in place. Thoroughly seal all cut surfaces with grafting wax or grafting paint to keep out water & prevent drying. If both scions in the cleft “take,” one will generally grow more rapidly than the other. After the first growing season, select the stronger scion and prune out the weaker.
The temperature of grafting wax is very critical. It must be hot sufficient to flow, but not so hot as to kill plant tissue. Recently, paint-like sealants have replaced wax in many areas because they are easier to use and want no heating.
Application of Cleft Grafting:
The application of Cleft grafting is generally performed several too many feet up from ground level, in an established tree. As such, it is a top working or high working system. It is used to change over an established fruit variety to a new variety, or to obtain multiple varieties on a single tree, or to insert a branch for self-incompatible trees like apple. Cleft grafting is used for grafting one or smaller diameter scions (5 to 10 mm) onto a larger stock (5 cm or greater).
The timing for Cleft Grafting:
The best Timing for Cleft grafting is performed in the early spring just as the stock plant is beginning to become active (bud swelling, etc.). On the other hand, it is preferable to utilize scion wood that more or less fully dormant (phonologically some weeks “behind” the stock). This may be able by collecting scion wood several weeks or earlier, during the winter, and storing under refrigeration, in a little moist cloth or another medium.
How to make a Cleft Grafting?
The Cleft grafting procedure is conducted in late winter when both the rootstock and the scion are in a dormant condition. The plant propagation in Cleft grafting will be done by the following procedure;
Common applications for Cleft grafting have changed the variety of an existing orchard (top working), adding a branch of an untested scion cultivar to an existing tree for observation. Repairing a tree that can have had a branch broken off by storm damage or fruit overloading.
The limb to be grafted or top worked is cut square with a pruning saw. The branch is then split in the middle longitudinally using a chisel, large knife, or a special tool that is a combination blade or wedge designed specifically for Cleft grafting. The limb is split for a distance of two to four inches, with care taken to make the split in the middle of the limb. For species which do not split evenly, the initial cut may need to be completed with a saw to prevent uneven splitting.
After the split is made, the “Cleft” is open & held open by the wedge end of the grafting tool or another suitable instrument to hold the cleft open. A three to four bud scion stick between 4 and 6 inches in length is then prepared for grafting into the cleft. The bud stick must be obtained from small limbs or water sprouts that grew vigorously during the past season of growth (1/4 to 3/8 inch in diameter) as indicated by well spaced, large plump buds. Very large diameter sprouts and ones which are small and thin with closely spaced buds must be avoided.
The lower end of the bud stick is trimmed with slowly sloping cuts made on exactly opposite sides of the stick. The slope of the cuts on the bud stick must match the angle of the cleft as closely as possible. The sloping cuts on the bud stick must exactly match the shape of the cleft in the rootstock. Furthermore, the cuts must be even in slope to allow for maximum contact between the bud stick & the rootstock for the entire length of the bud stick. If the bud stick is too blunt, the amount of contact will be very small to promote good healing of the union.
When the bud stick is inserted into the cleft, the cambia of the two pieces must be matched accurately to promote good healing. The cambium is accepted as the faint line that separates the bark from the wood. The bark of the rootstock will likely be much thicker than the bark on the bud stick, so the outer edges of the bud stick & rootstock will not be flush.
The ability to support the two partners to be grafted & maximizing the contact between the two pieces to promote rapid healing are the two principal determinants of success in cleft grafting. The natural spring in the wood must be sufficient to hold the bud sticks in place. After both bud sticks have been inserted & aligned, the wedge holding the cleft open is carefully removed. The cut ends of the bud sticks, the cut end of the rootstock, and the splits of the cleft are painted with grafting wax to stop desiccation of the wood.
The bud sticks should break buds readily during the subsequent spring development flush. If both bud sticks survive and resume growth, the less vigorous one must be cut away being careful not to dislodge the other one. A decision on which one to remove can wait a month or so to see which grows out stronger. However, under no circumstances must both bud sticks be allowed to remain for the entire growing season since complete healing of the wound will not happen with both in place.
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Good advice