by Kenny Popp

Tools for grafting

Knives

For propagation work, a well built sturdy knife of high carbon steel is essential. The knife must be kept razor sharp.

Grafting wax

Grafting wax has two chief purposes: (a) It seals over the graft union, thereby preventing the loss of moisture and death of the tender, exposed cells of the cut surfaces of the scion and stock. (b) It prevents the entrance of various decaying organisms that may lead to wood rotting.

An ideal grafting wax should adhere well to the plant surfaces, not be washed off by rains, not be so brittle as to crack and chip during cold weather, or so soft that it will melt and run off during hot days, but still be pliable enough to allow for swelling of the scion and growth enlargement of the stock without cracking.

For small scale operations, grafting waxes are available in aerosol applicator cans. Several repeated applications of this type of wax are generally needed.

Tying and wrapping materials

Some of the grafting methods, particularly the whip graft, require the graft union be held together by tying until the parts unite. Tying can be done in several ways-the simplest would be merely tying with ordinary string and covering with grafting wax. Waxed string is convenient because it will adhere to itself and to the plant parts without tying. It should be strong enough to hold the grafted parts together yet weak enough to be broken by hand.

A special nurseryman's adhesive tape is manufactured that is similar to surgical adhesive tape but lighter in weight and not sterilized. It is more convenient to use than waxed cloth tape. When using any kind of tape or string for wrapping grafts, it is important not to use too many layers or the material may eventually girdle the plant unless it is cut. It is best to observe such wrappings carefully and cut them after the graft has healed.

Plastic polyethylene, PVC, and masking tape are also satisfactory wrapping materials.

Approach Grafting

The distinguishing feature of approach grafting is that two independent, self-sustaining plants are grafted together. After a union has occurred, the top of the stock plant is removed above the graft and the base of the scion plant is removed below the graft. Sometimes it is necessary to sever these parts gradually rather than all at once. Approach grafting provides a means of establishing a graft union between certain plants in which successful graft unions are difficult to obtain. Approach grafting is usually performed with one or both of the plants to be grafted growing in a container.

This type of grafting should be done at times of the year when growth is active and rapid healing of the graft union will take place. As in the other methods of grafting, the cut surfaces should be securely fastened together then covered with grafting wax to prevent drying of the tissues.

Spliced approach graft

In the spliced approach graft the two stems should be approximately the same size. At the point where the union is to occur a slice of bark and wood 1 to 2 inches long is cut from both stems. This cut should be the same size on so that identical cambium patterns will be made. The cuts must be perfectly smooth and as nearly flat as possible so that when they are pressed together there will be close contact of the cambium layers. The two cut surfaces are then bound tightly together string, raffia, or nurseryman's tape. The whole union should be covered with grafting wax. After the parts are well united, which may require considerable time in some cases, the stock above the union and the scion below the union are cut, and the graft is then completed. It may be necessary to reduce the leaf area of the scion if it is more than the root system of the stock can sustain.

Tongued approach graft

The tongued approach graft is the same as the spliced approach graft except that after the first cut is made in each stem to be joined, a second cut- downward on the stock and upward on the scion –is made, thus providing a thin tongue on each piece. By interlocking these tongues a very tight, closely fitting graft union can be obtained.

Inlay approach graft

The inlay approach graft may be used if the bark on the stock plant is considerably thicker than that of the scion plant. A narrow slot 3 to 4 inches long is made in the bark of the stock plant by making two parallel knife cuts and removing the strip of bark between. This can be done only when the stock plant is actively growing and the bark slipping. The slot should be exactly as wide as the scion to be inserted. The stem of the scion plant, at the point of union, should be given a long, shallow cut along one side, of the same length as the slot in the stock plant and deep enough to go through the bark slightly into the wood. This cut surface of the scion branch should be laid into the slot cut into the stock plant and held there by nailing with 2 or more small, flat headed wire nails. The entire union must be thoroughly covered with grafting wax. After the union has healed, the stock can be cut off above the graft and the scion below the graft.

See figure 1

Inarching

Inarching is similar to approach grafting in that both stock and scion plants are on their own roots at the time of the grafting: it differs in that the top of the new rootstock plant usually does not extend above the point of the graft union as it does in approach grafting. Inarching is generally considered to be a form of "repair grafting," used to repair roots damaged by cultivation implements, rodents, or disease. It can be used to very good advantage in saving a valuable tree or improving a root system.

Seedlings planted beside the older, damaged tree, are grafted into the trunk of the tree to provide a new root system to supplant the damaged roots. A satisfactory procedure for inarching is to plant seedlings of a compatible species around the tree during the dormant season. Then the grafting operation can be done as active growth commences in early spring.

A long slot is made on the trunk of the older tree by removing a piece of bark the exact width of the seedling and just as long as the cut surface made on the seedling. A small flap of bark is left at the upper end of the slot, under which the wedge end of the seedling is inserted. Then the seedling is nailed into the slot with four or five small, flat headed wire nails. The nail at the top of the slot should go through the flap of bark and through the end of the seedling. If any of the bark of the tree along the sides of the seedling should accidentally be pulled loose, it is necessary to nail it back in place. After nailing, the entire area of the graft union should be thoroughly waxed.

Most of the above information applies to commercial operations, but the techniques can be adapted to enhance our Bonsai.

I have seen in a Bonsai article some years ago where a limb may be allowed to grow very long and bent around to be inserted in a hole drilled through the trunk to come out the other side in a desired future limb position. The cambium must be removed and the limb fit to the hole very snug. This type of graft will most likely leave the most natural appearance. I have not tried this yet. The article was about this procedure on an American Hornbeam. You will need to taper the cambium on the limb so as not to remove it all as you pull it through the hole. Hopefully it will grow back. It may need to be waxed. Deciduous trees should take faster. I would think it would be the best approach as the limb angle would be your choice. As with anything you are not familiar with, you should try this on a tree that is in your yard or in a wooded area.

I have successfully completed 2 Inarch grafts on a Western White Pine (Pinus monticola) by removing the cambium on both the limb and the trunk, and bending the limb up against the trunk. The sap from the pine closed the wound. I wrapped the limb to the trunk with electrical tape and copper wire. I then monitored the growth. In one season I loosened the wire, but kept it on for another year to protect the limb from birds breaking it off. I made the graft in the spring and kept it out of the full sun. I did remove the tape late in the season as it seemed to get too tight.

In this case the limbs were not cut off, which is what allowed the trunk to heal and taper quickly. See photos.

If this were done with the limb base to be removed, as in a more distant limb location, I think I would cut off parts of the limb over time, maybe 3 to 6 months, or 1/2 each season. Deciduous trees will need a grafting wax, over the tape.

Remember, Patience and not being afraid to learn something new can be very rewarding.

Ref:
Plant propagation Principles and Practices Hartmann and Kester
Bonsai Its at Science, and Philosophy Deborah Koreshoff
Bonsai techniques John Naka