Plant Propagation and Nursery Management (1+1)

Detached Scion Grafting

A. Apical grafting

Splice or whip grafting:

• In this method, it is essential that both the stock and scion should be of equal diameter. The various steps involved in splice grafting are shown in Plate 7.1.
• For this, about one-year-old rootstock is headed back at a height of 20-25 cm from the soil and a splice (diagonal) cut of 2.5 to 6 cm long is made at the distal end of the rootstock with the help of a sharp knife.


Plate 7.1: Splice or whip grafting

• A similar slanting cut is made on the proximal end of the scion. The cuts should be smooth and the cut surface of both the rootstock and scion are bound together and tied firmly with polythene strip.
• After the union has taken place, the rootstock above the union is lopped off gradually. Sprouts arising below the grafting union must be removed at regular intervals to divert flow of metabolites for the growth of scion only.
Whip and tongue grafting:
• It is modified form of whip grafting. It differs from whip grafting that a reverse cut is made downward at a point about 1/3rd of the distance from the tip and should be about ½ the length of first cut.
• The various steps involved in splice grafting are shown in Plate 7.2. To obtain a smooth-fitting graft, the cut should not split.
• The rootstock and scion is then inserted into each other, with the tongues interlocking. It is important that vascular cambium layer match along at least one side, preferably along both sides.

Plate 7.2: Steps involved in tongue grafting

• The lower tip of the scion should not overhang the stock as there is a likely hood of the formation of large callus knots.
• The use of scions larger than root stock should be avoided. After the scion and rootstock are fitted together, they should be securely held by tying with budding/grafting tape or polythene.
• This method gives better success than splice grafting because of better cambial contact between stock and scion due to formation of tongue.
• Regular de-shooting of sprouts on stock is required to obtain better growth of scion.
Cleft grafting:

• It is one of the oldest methods of field grafting. It is used to top work trees, either in the trunk of a small tree or in the scaffold branches of a bigger tree.
• The various steps are shown in Plate 7.3. In making the cleft-graft, a heavy knife is used to make a vertical split for a distance of 5 to 8 cm down the center of the stub to be grafted. This split is made by pounding the knife in with a hammer.
• The branch is sawed off in such a way that the end of the stub is smooth and free from knots for at least 15 cm.


Plate 7.3: Steps involved in cleft grafting

• In this method, two scions are inserted, one at each side of the stock where the vascular cambium layer is located. The scions should be 8 to 10 cm long and 10-15 mm in thickness and should have two or three buds.
• The side of the wedge, which is to go to the outer side of the rootstock should be slightly wider than the inside edge. When the knife is removed, a hard wooden wedge is inserted to keep it open for the subsequent insertion of the scion.
• The graft should be wrapped with a polyethylene strip properly to prevent wilting of the scion. The scion starts growing after 2 to 3 months of grafting. The right time for cleft grafting is the later part of the dormant season or just before the start of active growth.
• Pear, walnut, hazelnut, pecan nut and grapes are propagated by this method.
Wedge grafting (saw-kerf grafting):

• It is performed in late winter or early spring before the bark begins to slip. A sharp, heavy, short bladed knife is used for making a V-wedge in the side of the stub or stock about 5cm long.
• Two cuts are made, coming together at bottom and as far apart at the top as the width of the scion (Fig.7.2). These cuts extend about 2 cm deep into the side of the stub.
• The base of the scion is trimmed and a wedge shape cut exactly the same size and shape as the opening. With the two vascular cambium layers matching the scion is tapped downward firmly into place and slanting outward slightly at the top so that the vascular cambium layers cross.
• After all scions are firmly tapped into place, all cut surfaces including the tips of the scion, should be waxed thoroughly. It is called saw-kerf grafting because the cuts in the side of the rootstock can be made with a saw rather than the sharp knife.


Fig.7.2: Wedge grafting

Saddle grafting:

• The saddle grafting can be bench grafted by hand or machine. The rootstock and scion should be of the same size. The scion is prepared by cutting upward through the bark and into the wood opposite sides of the scion.
• The knife should penetrate more deeply into the wood as the cuts are lengthened. Before the scion piece, and the saddle shape is gradually formed by removing pieces of the wood.
• The rootstock is cut transversely and then two upward cuts are made on either side. The apex of the rootstock is carved to fit the saddle so that vascular cambia of both stock and scion match.
• The graft is tied and cut surfaces are sealed by polythene until the graft-union is formed.
• t is used for the propagation of grape and rhododendron cultivars.
B. Side grafting methods

Side veneer grafting:

• This method is used for grafting small potted plants such as seedling of deciduous trees, shrubs and fruit crops. A shallow downward and inward cut from 2.5-3.5 cm long is made.
• At the base of this cut, a second short inward and downward cut is made, inserting the first cut, so as to remove the piece of wood and bark.
• The scion is prepared with a long cut along one side and very short one at the base of the scion on the opposite side.
• These scion cuts should be of the same length and width as those made in the rootstock so that the vascular cambium layers can be matched as closely as possible. After inserting the scion, the graft is tightly wrapped with polythene strips.
• After the union has healed, the rootstock can be cut back above the scion in gradual steps. This method is commercially used for raising mango and walnut plants.
Side-tongue grafting:

• In this method, the cut is made at the base of the scion, like the cut made in whip-and tongue graft. Then, a thin piece of bark and wood from stock and scion is completely removed.
• Then a reverse cut is made downward in the cut on the rootstock starting 1/3rd of the distance from the top of the cut. This second cut in the rootstock should be of the same length as the reverse cut in the scion.
• The scion is then inserted into the cut of the rootstock, the two tongues interlocking, and the vascular cambium matching. The graft is wrapped tightly, to avoid desiccation.
• The top of the graft union is left intact for several weeks until the graft union is healed and may be cut afterwards above the scion gradually so that the buds on the scion are forced into active growth.
C. Detached scion grafting methods

Bark Grafting (Rind grafting):

• It is very simple method of propagation and some nurserymen prefer it, because it can be done without splitting the stub, which prevents the entry of pathogens.
• It can be done in branches, which are 25 to 30 cm long. It should be done in spring when the bark of the stock slips easily.
• It is important to note that the scion used in bark grafting should be dormant. The rootstock is first sawed off at a point, where bark is smooth. If the stock is thick many scions can be inserted.
• For each scion, bark is split downward, about 5 cm from the top of the stub. Scions of 10-12cm length containing 2-3 buds are prepared by giving a slanting cut (5cm) downward along one side of the base.
• On the other side, a small cut is made. The scion is then inserted in the centre of split between the bark and wood of the rootstock. The longer cut of the scion is placed against the wood.
• The scion is held firmly by using adhesive tape. Afterwards, all the exposed portions of the stub and scion should be tied with polyethylene strip tightly. The scions will start sprouting after 6-8 weeks in case of successful grafts.
D. Root grafting (Whole root and Piece-root grafting):

• In this method, the seedling rootstock, rooted cuttings or layered plant is dug up and the roots are used as the rootstock for the graft.
• The entire root system may be used (whole-root graft) or the roots may be cut into small pieces and each piece is used as a rootstock (piece-root graft). As the roots used are relatively small (0.5-1.5 cm) in diameter, the whip and tongue graft is generally used. Root grating is usually bench grafted indoor during the late winter or early spring.
• In preparation of root-grafts, the root-pieces should be 7.5 to 15.0 cm long and the scions of about the same length containing two to four buds are used.
• After the grafts are made and tied properly, they are bundled together in groups of 50 to 100 and stored for callusing in damp sand, peat moss or other packing material.