Implications of Grafting

Grafting involves uniting living parts of plants so that they form a permanent union. One plant supplies the root system only and is called the ‘stock’. A small part of the plant of the variety required is joined to the stock and is known as the ‘scion’.

This eventually produces the shoots and branches. lt is essential that the stock and scion should be compatible. This indicates that they need to unite or grow together. ln most cases they are of the same genus. Sometimes plants of different genera can be grafted, like amelanchier on to sorbus aucuparia.

The selection of stocks involves careful consideration. Varieties of holly can be grafted on to the common holly; crab apples on to the common crab or apple stocks; ornamental peaches, plums and almonds on to common mussel plum stock; ornamental cherries on to Pnmux avium, the Gean or wild cherry; rhododendrons on to R. panticum; amelanchier and varieties of mountain ash on to sorbus aucuparia; crataegus varieties on to the common quickthorn and labumums on to vulgare.

You will notice that most plant varieties are grafted on to their common counterparts. Preparation of stocks requires buying them from a nurseryman and planted in rich, well-prepared soil during October or November. They are then left to grow until the following March when grafting can take place. During this time it pays to rub off all buds on the stems 9 to 12 inches from the ground. Selecting the scions is also important.

The one year old shoots for grafting are best as these are not too thick. They can be cut from the parent plant in February, tied in bundles and heeled in under a north wall until they are required in March. Just before use they must be washed free of soil. Whip and tongue grafting are popular methods used for many trees and shrubs. For this, and any other type of grafting, always use a really sharp knife. First, the stock is cut down to within 3 or 4 inches off the ground. Then a slanting upward cut about an inch long is made at the top of the stock.

This should remove about half the thickness of the stock. Then a small downward cut is made in the cut surface near the top. This forms a `tongue’. To prepare the scion the selected shoots are cut so that each piece contains three or four buds. Do not use the soft tips of the shoots. The base of the scion is prepared by making a slanting downward cut similar to the one on the stock. Then a tongue is cut so that it corresponds with the one on the stock.

The tongue of the scion is fitted into the one on the stock. lf the cut surfaces are perfectly smooth they will fit closely together. The graft is then bound very tightly and then covered with grafting wax to render it airtight and watertight. lf the widths of stock and scion differ, then it is essential that one side of each should meet perfectly. This is to allow the cambium layers that are seen immediately under the bark of stock and scion to unite. Unless the cambium layers meet somewhere a union will not occur. Once the scion is growing vigorously, the shoots or buds which appear on the stock should be rubbed out regularly.