Method and apparatus for horticultural grafting

A method and apparatus are disclosed for making improved grafting joints between plant components, particularly woody plants. Selected plant materials may be grafted one upon another by cutting out two diametrically opposed longitudinal 90.degree. sectors from each end of the plant parts to be joined. The sectors are of equal length on each plant part and are joined by slipping the sectored end of one plant part into the cooperating sectored end of the other plant part so that the parts interlock. The joint is then enveloped by tape or the like to seal the joint. Tools for making uniform, repeatable grafting cuts are disclosed, including a simple gauge block with an integral cutter. The tool includes a socket bisected by a blade for making a cut of uniform depth lengthwise down the center of the plant and at least one gauging groove having a transverse cutting edge to make the transverse cut to remove the sector from the slit plant. Hand tools and semi-automatic machinery are also disclosed for sectoring plants in a single operation and include radial cutting discs arranged perpendicularly to one another and adapted to make four simultaneous 90.degree. slits lengthwise along the plant and reciprocating perpendicular cutting elements to remove the opposing slit sectors.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to horticultural grafting and is more 
particularly directed toward a new and improved method and apparatus for 
making improved graft joints between plant parts, particularly woody 
plants. 
2. Description of the Prior Art 
The grafting of a scion upon a rootstock is a common horticultural practice 
used in the propagation of woody plants. The technique is used widely in 
the propagation of fruit tree varieties, since bench grafting may be 
performed during the dormant season of the plant as opposed to field 
budding during the growing season. Grafting provides the opportunity to 
build not only the conventional rootstock/scion tree, but also allows for 
a more complex interstem tree which may have as many as four selected 
plant materials grafted in series, one upon the other. 
In order to graft successfully one plant component to another, it is 
necessary that the cambium layers of the joined components be in direct 
contact with one another and that the union be physically strong. The most 
common technique for grafting woody plant components is by way of a whip 
graft in which the end of each plant component is cut diagonally at 
approximately the same angle with a counterslit made medially and 
lengthwise through the diagonal cut to form a tongue. The components are 
then joined so that the tongues are interlocked and the joint is then 
wrapped by twine or the like. While the whip graft is relatively simple in 
principle, it requires considerable skill in preparation in order to 
insure good cambium contact. Further, the strength of the union parallel 
to the tongue slit is not consistently good and such grafts normally must 
be tightly wrapped to provide stability. 
Accordingly, it is an object of the present invention to provide 
improvements in grafting techniques. Another object of the invention is to 
provide a grafting method adapted to produce a structurally strong 
grafting joint characterized by good cambium contact. A further object of 
this invention is to provide apparatus to carry out the improved grafting 
methods on a uniform, highly-repeatable basis. 
SUMMARY OF THE INVENTION 
This invention features the method of grafting a plant component to another 
plant component of substantially corresponding diameter, comprising the 
steps of removing a pair of longitudinal, diametrically opposed, 
90.degree. sectors from the end of each part to be joined, joining the 
sectored ends and then wrapping the ends. 
Apparatus for cutting out the sectors for the grafting operation includes a 
combination cutting tool and gauge block formed with a socket bisected by 
a cutting element by means of which a plant end may be inserted in the 
socket against the cutter up against the back wall of the socket to form a 
longitudinal, diametrical slit, first at one angle and then a second slit 
at a 90.degree. angle thereto. The branch end is then removed and laid in 
a groove formed in one wall of the block and having a cutting edge 
extending into the groove to sever opposing slit sectors from the branch. 
In another embodiment of the invention four radially arrayed cutting 
wheels are positioned at 90.degree. angles and have their cutting edges 
joining a common point whereby a branch stem pressed between the wheels 
will be slit longitudinally in one stroke. Reciprocating trimming blades 
are then brought to bear at opposite sides of the branch to trim away the 
opposing sectors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings and to FIGS. 1 through 5 in particular, there 
are illustrated the steps of preparing and grafting one plant component to 
another according to the invention. For purposes of discussion, the 
process will be described in connection with the grafting of a scion 10 to 
a rootstock 12 for a woody plant such as a fruit tree or the like, 
although obviously the technique is applicable to other grafting 
situations. Initially a scion 10 is trimmed evenly at one end which is to 
be grafted to the opposing end of the rootstock 12, which is similarly 
prepared. Since the operations carried on in preparing the rootstock are 
identical to the preparations carried on in connection with the scion, 
only one procedure will be described. As shown in FIGS. 1 and 2, the scion 
10, after the end has been trimmed straight across at a right angle, a 
pair of mutually perpendicular longitudinal slits are made along the 
trimmed end to form four equal longitudinal sectors. A pair of 
diametrically opposite sectors 14 and 16 are then severed at their 
respective bases and removed from the end of the scion. These sectors are 
of equal length and have a length which should be sufficient to form a 
good cambium contact and structural strength with the similarly prepared 
end of the rootstock 12. For small trees having a diameter of perhaps 1/4 
inch, for example, a sector length on the order of 3/4 inch has proven to 
produce satisfactory results. For larger diameter specimens, the sectors 
may be made longer. In practice, the sectors may be removed by forming 
longitudinal diametrical slits along the centerline of the scion, each 
slit being made at a 90.degree. angle with respect to the other. Once the 
two slits have been made, a cut is made at the end of the slit 
approximately 3/4 inch back from the trimmed end of the scion, one cut at 
each side. The cut is made radially inward and is pie-shaped in order to 
remove only the segment without cutting into the remaining portion of the 
plant. This operation is repeated on the rootstock 12 so that both ends 
are formed with similar sectored cuts allowing the two sections to be 
joined together in end-to-end interlocking relation as shown in FIGS. 3 
and 4. 
In practice, the scion and the root stock 12 should be of substantially 
equal diameter to insure proper fit and proper grafting results. Once the 
ends are joined together they should be bound in order to seal the joint 
and to add to the structural stability of the plant until such time as the 
two parts have grown together. In practice, satisfactory results have been 
achieved using a pressure sensitive adhesive tape 18, preferably a black 
plastic tape, which yields a strong joint in all directions, but is not 
subject to the girdling which can result from the use of a hard cord wrap, 
such as is commonly used in whip grafting operations. The tape is wrapped 
helically about the joint, fully enclosing it in the manner suggested in 
FIG. 4. In lieu of the use of pressure sensitive adhesive tape, the joint 
may also be secured by means of heat-shrinkable plastic tubing slipped 
over the joint and selected in a size that the tubing initially will be 
larger than the diameter of the plant sections and will, under the 
application of heat, shrink onto the joined sections to form a tight 
sealed joint. 
Referring now to FIGS. 6 through 9, there is illustrated a simple, 
inexpensive combination gauge block and cutting tool for use in performing 
the grafting operations of FIGS. 1 through 5. The tool is generally 
indicated by the reference character 20, and in the illustrated embodiment 
is in the form of a block 22 small enough to be held in the hand and, by 
way of example, may have a height of perhaps 2-1/4 inches and a width and 
thickness each of perhaps 1-1/4 inches. Obviously, these dimensions are 
only by way of example and may be altered according to the average 
diameter of the plants involved. The block 22 may be made of a variety of 
material, such as metal, plastic or the like, and may be made by various 
techniques such as injection molding, casting, machining or the like. In 
any event, the block 22, which may be of one-piece construction or may be 
assembled from different parts, includes a socket 24 formed 
perpendicularly through the block, originating at a block face 26 and 
terminating at a window 28 in an opposite face 30 of the block 22. If the 
block is to be of one-piece construction, preferably it is made of a clear 
plastic material which allows the worker to view the end of a branch or 
rootstock which is inserted in the socket 24 for reasons that will 
presently appear. If the block is to be assembled from several different 
components then the wall defining the face 30 at least should be of a 
clear transparent material, such as acrylic plastic or the like. In any 
event, the window 28 is located at the inner end of the socket 24 and 
preferably the socket 24 should be a tilted square in cross-section. 
Although the particular shape is not critical, the V-groove formed in the 
socket aids in centering a branch in the socket. 
Mounted within the block 22 and extending diagonally and vertically across 
the socket 24 is a slitter 32 in the form of a thin cutting blade whose 
leading cutting edge faces the open end of the socket 24 but is recessed 
from the face 26. The rear edge of the slitter 32 bears against the window 
28 at the rear of the socket while triangular ends 42 and 44 of the 
slitter project upwardly and downwardly, respectively, into channels 34 
and 36 formed respectively in the top and bottom faces 38 and 40 of the 
block 22. Typically, the depth of the slitter is on the order of 3/4 inch 
with a length of perhaps 2 inches along its leading cutting edge. The 
socket 24 typically has a maximum width of perhaps 3/4 inch at its widest 
point. 
The channels 34 and 36 are arranged parallel to one another and 
perpendicular to the length of the socket 24 so that the angular corners 
42 and 44 of the slitter 32 will be oriented transversely to the length of 
the channels. Each channel is open at one end and closed by means of a 
wall 46 and 48 at the other end. These walls form a part of a face of the 
block and serve as a stop and gauge for a branch laid into the channel. 
The distance between each blade corner 42 and 44 and its respective wall 
46 and 48 substantially corresponds with the distance between the cutting 
edge of the slitter 32 and the back wall of the socket 24, namely 3/4 
inch, in the illustrated embodiment. 
The tool of FIGS. 6 through 9 is used to produce the grafting operations of 
FIGS. 1 through 5 in the following manner. First of all, the worker 
selects the components which are to be grafted to one another, first 
making certain that the components are of substantially corresponding 
diameter. Once the components are selected, the facing ends are prepared 
by making a smooth perpendicular cut. Next, taking one component at a 
time, the cut end of a component is placed in the socket 24 positioned in 
the bottom of the internal V-groove defined by the socket. The component 
is then pressed forward against the slitter 32 until the end comes up 
against the inner face of the window 28. This operation will produce a 
diametrical slit approximately 3/4 inch lengthwise through the end of the 
component. The slit component is then withdrawn, rotated 90.degree. and 
again placed in the socket and pushed in against the slitter to produce a 
second diametrical lengthwise slit oriented 90.degree. with respect to the 
first slit and of the same depth. The transparent window 28 at this point 
is useful since it allows the worker to sight through the transparent 
window, which also serves as a stop and a gauge and allows him to verify 
the angular position of the work. 
Once the second slit has been made, the component is withdrawn from the 
socket and placed in one of the channels 34 or 36. The component is placed 
in the channel so that the component end is butt against either wall 46 or 
48 and aligned with the V-channel defined by the bottom of each channel. 
Using a rocking motion, the worker presses the component down against the 
blade 42 or 44 so as to sever and remove one sector 14 or 16. The worker 
then rotates the component 180.degree. and repeats the step so as to 
remove the diametrically opposite sector 14 or 16. 
The trimming, slitting and severing operations are then repeated for the 
other component of a plant so that both ends are sectored in the same 
manner. The component ends are then joined, as suggested in FIGS. 3 and 4, 
interlocked and sealed by tape, heat-shrinkable tubing, or the like. It 
will thus be appreciated that the blade 32 is so positioned with respect 
to the block that all cuts are made to the same dimension to insure 
uniformity in the sectoring of components to be joined. 
Referring now to FIGS. 10 and 11, there is illustrated a modification of 
the invention, and in this embodiment there is shown an apparatus for 
producing the slitting and sectored cutting in a single operation. The 
apparatus includes a fixed support 50 having a flat, vertical front face 
52, which serves as a stop and a gauge for a component applied against it. 
Extending forwardly from the support 50 are arms 54 and 56, each carrying 
a pair of slitting discs 58, 60, 62 and 64. The discs 58 through 62 are 
arrayed at right angles to one another with their cutting edges 
substantially contacting one another along a center line perpendicular to 
the face 52 as best shown in FIG. 11. The slitting discs are carried by 
bearings 64 mounted to the respective fingers 54 and 56 and freely 
rotatable. The point of contact of the slitting discs is located along the 
center line and spaced from the face 52 by a distance corresponding to the 
depth of the slit to be made in the component. In this fashion a 
component, once its end has been prepared by making a perpendicular cut, 
is fed along the center line and into the bite of the slitting disc toward 
the face 52 of the support 50. When the component is fed into the bite of 
the discs, four slits will be made automatically, lengthwise in the end of 
the component to a desired, repeatable depth, the component being pressed 
up against the face 52 to insure that all slits are made to the same 
depth. 
In the illustrated embodiment of FIG. 10, a microswitch 56 is provided 
along the center line in the face 52 and at the end of the path of travel 
of the component being fed between the slitters. When the component 
contacts the switch 66 the switch will close, completing a circuit through 
a lead 68 to actuators 70 and 72, causing the trimming blades 74 and 76 to 
reciprocate toward one another in directions perpendicular to the length 
of the component and parallel to the face 52. The trimming blades are 
located diametrically opposite one another, as shown in FIG. 11, and in a 
plane passing through the point of contact for the slitting discs. The 
blades 74 and 76 are formed with right angular cutting tips which move in 
against the component cutting away the opposing slit sectors 14 and 16. 
The component is then withdrawn and the sectors 14 and 16 drop away. The 
operation is repeated for the other component and the parts are joined as 
before. 
Referring now more particularly to FIG. 12, there is illustrated a 
hand-operated tool 78 embodying the features of the FIGS. 10 and 11 
apparatus and comprised of a handle 80, on one end of which is mounted a 
cage 82 formed by an annulus 84 spaced from the flat face 86 on the 
forward end of the handle 80. The annulus is supported to the handle by 
means of frame members 88 and 90 which also carry four slitting discs 92, 
94, 96 and 98 arrayed perpendicular to one another in the same manner as 
in FIGS. 10 and 11 embodiment and spaced from the face 86 in similar 
fashion. Trimming blades 100 and 102 are located in the same relative 
position with respect to the discs, as in the FIGS. 10 and 11 embodiment, 
but in this instance are carried by lever arms 104 and 106, the forward 
ends of which are pivoted by hinges 108 and 110 on the annulus 84. The 
lever arms extend rearwardly, generally parallel with the handle 80, with 
the rear ends thereof turned into the handle, the rear of which is hollow 
to accommodate a spring 112 serving to keep the lever handles 104 and 106 
and their cutting blades 100 and 102 in the open or extended position. 
The tool is used in the manner similar to the FIGS. 10 and 11 embodiment, 
with the component being fed axially into the bite of the slitting discs 
to butt against the face 86 of the handle. Once in this position, the 
lever arms 104 and 106 are squeezed, causing the blades 100 and 102 to cut 
into the component trimming away the slit sectors, and the component is 
then withdrawn. 
In FIG. 13 there is illustrated a tool 20' similar to the tool 20 of FIGS. 
6 through 9, with the exception that in place of a transparent window at 
the end of the socket 24', the face 30' is formed with an opening 28' 
smaller than the socket 24' and defining a shoulder stop 114 at the inner 
end of the socket. 
While the invention has been described with particular reference to the 
illustrated embodiment, numerous modifications thereto appear to those 
skilled in the art.