Grafting is a technique of joining two parts of different plants together in such a way that they will unite and continue their growth as one plant.
One part, called the scion, is usually a stem from the plant to be propagated. This is grafted on to a root system from another plant, which is called the rootstock (also, the stock or understock). All the various techniques of joining plants are called grafting, although, when buds only are joined to the rootstock, it is sometimes called budding.
There are two basic grafting positions: apical grafting, in which the top of the root-stock is removed and is replaced with the scion; and side grafting, in which the scion is grafted on to the side of the rootstock and the rootstock above the graft is not removed until after a union is achieved.
Because time-consuming preparation work is necessary before two plants can be joined, grafting is superficially a less attractive technique than other relatively easy methods of vegetative propagation, such as taking stem
THE ADVANTAGES POSSESSED BY VARIOUS ROOTSTOCKS
East Mailing series (EM) Mailing Merton series (MM)
Colt, F12/1 East Mailing quince Brompton, Pixie, St Julien A Rhododendron 'Cunningham's White' Rosa chinensis 'Manetti'
Resists woolly aphids and controls vigour
Tolerates up to pH7
Tolerates soil moisture and salt concentration
Does not produce suckers, has few thorns and has long hypocotyl
1 Select a plant that will be suitable as rootstock. Plant it outdoors. Label and leave for a growing season.
2 Select a plant that is suitable as scion material. Cut off some vigorous hardwood stems for scions.
3 Bundle these scions together. Heel them into the ground in a well-drained, cool place. Label.
cuttings or layering. However, some plants such as witch-hazel are not easily propagated by any other vegetative method if selected forms are required, and so they are grafted on to rootstocks.
Perhaps the most useful reason for grafting is to transfer the benefits of a particular rootstock on to another plant. Various fruit-tree rootstocks, for example, have been developed to control both the size and fruiting vigour of other varieties of fruit tree. Other advantages that a rootstock might possess are resistance to pests and diseases; toleration of high soil-moisture levels and salt concentrations; and toleration of high alkalinity levels in the soil. The more rootstock incorporated into a new plant, the more influence the rootstock will have.
Another advantage of grafting is that more than one scion can be joined on to a plant. This is particularly useful with fruit trees as a suitable pollinator variety can be grafted into a tree or bush already grafted with another variety, or it may allow a decorative stem to be grafted on and then be top worked with another variety.
There are a number of problems associated with grafting. The main one is ensuring two plants are compatible. This limitation determines which variety and species of plants can be grafted on to which rootstocks; in general, it is normal to graft varieties on to their own species or very closely related ones.
To graft successfully, it is vitally important to position the various tissues of the stem correctly so that the stem can make a quick and continuous union. The cambium is the actively growing part of the stem that lies just under the bark. This cambium layer on both the scion and the rootstock must be positioned so they are absolutely adjacent to each other, or at least in as much contact as possible.
The successful formation of a graft also depends on making and matching cuts quickly and cleanly: the cut surfaces must be placed in contact with the minimum of delay. Should the surfaces dry out, the tissues will die and so make an effective barrier to the development of a successful union.
The making of a graft union is only partly due to successful carpentry. Much also
4 Trim the bottom 12-15 in on the rootstock of all branches just before the leaf-buds break.
5 Cut back the rootstock to where the scion is to be grafted. Make a 1j in sloping cut at the top.
6 Lift the scions from the ground. Make a top cut just above a bud about four buds from the base.
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