depends on providing suitable conditions for the tissues to develop and grow to form a successful union. In effect, this means that water loss must be prevented and warmth must be provided round the grafted parts by carefully covering them until they have joined together.
Traditionally, the grafted parts have been covered and tied together with raffia, but most grafts are now enclosed by ¿in wide clear polythene strip. This has the advantage of completely surrounding and sealing the cut areas, so reducing water loss to a minimum. The graft union on indoor grafted plants is taped with rubberized strip before being placed in a humid atmosphere to develop.
Once the grafted parts have successfully united, the development of the new plant depends on preventing any further competition from the rootstock. Therefore, always remove all subsequent growths from anywhere on the rootstock.
Although it is theoretically possible to graft at almost any time of the year, the best season for most grafting is in the spring.
Shield-budding, however, must normally wait until midsummer when the bark lifts easily from the wood on the rootstock.
Whip-and-tongue grafting is commonly used to propagate fruit trees, although the technique can be employed successfully for trees and shrubs with tissues that will also readily unite at relatively low temperatures.
Select a plant that will be suitable as root-stock and plant it outdoors. Label it and leave it to establish for one growing season.
In mid-winter, select a plant that is suitable as scion material. From it take some hardwood stems with all their previous season's growth. Bundle these scions together and heel them in 6 in of soil in a well-drained cool position. Firm back the soil and label them. When the scions are eventually grafted in spring, they will be less developed than the growth on the rootstock.
Prepare the rootstock once its sap has started to rise; this is usually just before the leaf-buds break. Trim to make a single stem with no branches.
7 Make a 1j in basal cut at the same angle as the rootstock cut. End it just below the bottom bud.
8 Make a shallow, single ^in slice into the rootstock from one-third down the sloping cut.
9 Make a shallow, single ^in slice into the scion from one-third up the scion sloping cut.
Fruit trees (especially apples) are grafted at 9-10 in above soil level to avoid problems such as collar rot. Ornamental plants, on the other hand, are grafted as close to the ground as feasible, to avoid unsightly bulges that may occur with certain rootstock/scion combinations.
Cut back the rootstock to the appropriate height with a pair of sharp secateurs. Then make a in sloping cut across the top, using a sharp knife.
Lift the scions from the ground. Select one that has a similar diameter at its base to that of the rootstock top. Take a sharp knife and make a top cut close above a bud about four to five buds from the scion base. Then make a sloping 1^in cut across the base of the scion, ending it just below a bud; ensure the cut is at the same angle as the rootstock cut.
This is a splice or whip graft. To provide rigidity, add a tongue to the cuts.
The tongue is made from single cuts on both the scion and rootstock. From one-third of the way down the sloping cut on top of the rootstock, make a shallow, single j in slice down into the rootstock.
Make the scion tongue by c utting for \ in from one-third of the way up the scion sloping cut, keeping the knife blade at the same angle as the tongue on the rootstoc k.
Slip the scion into the rootstock so they interlock. If the rootstock is thicker than the scion, move it to one side until there is good contact between the two cambial layers. Bind with clear polythene grafting tape to hold the join firmly. Seal the top of the scion with tree paint and label.
For a wide range of trees and shrubs, including apple and pear trees, the grafted parts can then be left to unite. Cherry trees, however, should have their scion and grafted area covered with a polythene bag, which is then tied just below the union—the increased temperature hastening development.
Remove the grafting tape and polythene bag as soon as the cut surfaces start callusing, which means the two grafted parts are beginning to join.
Cut off any growth that the rootstock may produce and, if required, reduce the scion shoots to just one to promote a single-stemmed tree or shrub.
11 Bind the join firmly with clear polythene tape. Dab the top of the scion with tree paint. Label.
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