Plant Propogation and Nursery Management

Approach Grafting

The characteristic features of approach grafting are that two independent, self-sustaining plants are grafted together. After the formation of union, the top of rootstock plant is removed above the graft union and the base of the scion plant is removed below the graft union.
Generally, it is performed with one or both of the plants to be grafted, which are growing in a container. Rootstock plants in containers may also be placed adjoining to an established plant, which is to furnish the scion part of the new grafted plant.
It must be performed in the season when plants are in active growth because under such conditions, rapid healing of the graft-union will take place. The important methods are:

Spliced approach grafting:

• In this method both scion and stock should be of same thickness. A splice of 4-5cm bark and wood is removed both from stock and scion (Fig.7.3).
• The cut on both the partners should be of the same size and should be smooth too. The cut surfaces of stock and scion are bound together with some suitable tying material and waxed properly.
• The stock above the union and scion below the union are cut after sometime, when proper union has taken place. It may be necessary to reduce the leaf area of the scion if it is more than the root system of the rootstock.

Fig.7.3: Spliced Approach Grafting

Tongue approach grafting:

• The tongue approach grafting is the same as the spliced approach grafting, 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, by providing a thin tongue on each piece(Fig.7.4).
• By interlocking these tongues tightly, a closely fitted graft union can be obtained.

Fig.7.4: Tongue approach

Approach grafting:

• The inlay approach grafting may be used if the base of the rootstock plant is considerably thicker than that of the scion plant. The various steps involved are shown in Fig.7.5.
• A narrow slot, 7.5 to 10 cm long is made in the bark of the rootstock plant by making two parallel cuts and removing the strip of bark between. This can be done only when the rootstock plant is actively growing and their bark slipping easily.
• 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 rootstock plant and deep enough to go through the bark and slightly into the wood.

Fig.7.5: Approach grafting

• This cut surface of the scion branch should be laid into the slot cut in the rootstock plant and held there by nailing with two or more small, flat headed wire nails. The entire union must then be thoroughly covered with grafting wax.
• After the union has healed, the rootstock can be cut off above the graft and the scion below the graft.

Inarching:

• Inarching is similar to approach grafting as rootstock and scion plants are on their own roots at the time of 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 used to replace roots damaged by cultivation equipments, rodents or diseases.
• It is very advantageous in saving a valuable tree or improving its root system (Fig.7.6 and Fig.7.7).
• In this method seedlings (or rooted cuttings) planted beside the damaged tree, or suckers arising near its base are grafted into the trunk of the tree to provide a new system to supplement the damaged roots.
• The seedlings to be inarched into the tree should be spaced about 10-15 cm apart around the circumference of the tree if the damage is extensive.
• The seeding of compatible species is planted around the tree during dormant season and grafted when active growth commences in them during early spring. Inarching will enhance growth of uninjured older trees.

Fig.7.6: Inarching technique

• A thin slice of bark (6-10 cm in length) at about 20 cm above the ground level is removed from the stock with a sharp knife. A similar cut is made in the scion. Thus, the cambium layers of both stock and scion are exposed. These cut are brought together and tied firmly with the help of a polythene strip.

Fig.7.7. Inarching Technique

• After the successful union, stock above and scion below the graft union are lopped off gradually. In low rainfall areas, it should be done with the onset of rains, while in regions of heavy rainfall; it should be done soon after the rainy season is over, provided temperature does not fall below 15⁰C.