>> Cleft Grafting
Application: Cleft grafting is usually performed several to many feet up from ground level, in an established tree. As such, it is a topworking or highworking technique. It is used to change over (rework) an established fruit (scion) variety to a new (more desirable) variety, or to obtain multiple varieties on a single tree, or to insert a pollinizer branch for self incompatible trees like apple. Cleft grafting is used for grafting one or more smaller diameter scions (5 to 10 mm) onto a larger stock (5 cm or greater). |
Timing: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 use scion wood that more or less fully dormant (phenologically several weeks "behind" the stock). This may be accomplished by collecting scion wood several weeks or more earlier, during the winter, and storing under refrigeration, in slightly moist cloth or other medium. This differential phenological activity between stock and scion allows vigorous callusing from the stock and later stages of graft union formation at the point of stock/scion union, but the relative dormancy of the scion delays leafing out and hence minimizes scion water stress. This is critical before vascular continuity is established, i.e. before new xylem forms across the graft union to facilitate water transport from stock to scion. |
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How to Cleft Graft: |
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Cleft grafting
is usually performed in the landscape or orchard on well established trees
(including full grown). Branches, well up in the canopy of the tree, are
cut back with a saw at a point where they are one to several inches in
diameter, for insertion of the scion(s). Often several branches on a single
tree are cleft grafted as shown. Cleft grafts are often placed several
to many feet above ground level.
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Chisel end
of the cleft grafting tool is centered and struck with a hammer to split
the stock.
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Base of scion
is cut to a V-shaped wedge for insertion into the stock
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The spreader
end of the tool is used to pry open the split in the stock while inserting
the scion. The carpentry itself generates pressure, so tying is not necessary.
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Two scions, 2 to 4 nodes long,
inserted at edges of stock (not centered) to assure cambial alignment.
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Melted grafting
wax is used to seal cuts from moisture loss and pathogen entry. Distil
ends of scions should be waxed as well. After graft union formation, the
weaker-growing of the two scions is removed (pruned back). Images 1687
and 1688 are from LH Bailey, 1928, Standard Cyclopedia of Horticulture,
Macmillin.
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Alternative
cleft grafting tool used in Kenya.
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Additional Information:
Source:
Univ. of Missouri Outreach & Extension |
Source:
Cornell Univ. Hort 400 Plant Propagation Web Page |
Source:
Texas A&M University, Research and Extension Resource/Aggie
Horticulture |
Source:
University of Minnesota Extension Service, College of Agricultural,
Food, and Environmental Sciences |
Source:
University of Minnesota Extension Service, College of Agricultural,
Food, and Environmental Sciences |