Gardening Techniques Part 4

A graft is the union between two plants, the roots and lower stem of one plant (which is known as the 'stock' or 'root stock') uniting with the shoot of another plant (the scion), so they grow together as one. The principle role of grafting in horticulture is the propagation of trees and shrubs where one or more of the following difficulties prevent easier means of manufacturing planting material.

Varieties which root slowly or not at all from cuttings or by layering.
Varieties which do not seed.
Varieties which don?t breed true from seed.
Varieties that are unsatisfactory when grown on their very own roots.

A mystique has grown up about grafting, but the principle is very simple. The stock and the scion have to be related, as a general rule the chance of a successful union increases in direct proportion to the closeness of the relationship. Next, there must be physical close contact, it is a thin living layer below the bark which has to knit together. Timing is vital, the plants should be just starting to grow after their winter set, and the union, or joint, has to be protected. This involves binding with raffia, plastic tape or an elastic tie and then covering the whole area with grafting wax. It will prevent both drying out and infection from air-borne spores.

Although the principle is simple, a large amount of systems have evolved over the centuries, saddle grafting, rind grafting, approach grafting, splice grafting and so on. The most well-liked method is whip and tongue grafting. The stock and scion should be approximately the same thickness, remove the binding material once the graft has taken and new growth has appeared.

Cacti are the easiest group of plants to graft. All you need to do is cut the base of the scion in the form of a V. Cut a corresponding V at the top of your stock and push the two grafts together. Push a few pins or thorns through the union and leave the remainder to nature.

Commercial Roses are generally propagated by budding, a type of grafting which is done in midsummer as opposed to early spring. A bud or 'eye' of the selected variety is inserted into a T-shaped cut made in the stem of your rootstock, close to the ground for a bush or some distance up the stem for a standard.

Hardening off:
Plants raised indoors or in a greenhouse have tender tissues, suddenly moving them indoors in spring means a transition period to colder conditions and drying winds for which they aren?t prepared for. The results of this shock is either a severe check to growth or death of the specimen, depending on the tenderness of your variety.

To avoid this problem there must be a gradual acclimatisation to the harsher conditions to be faced outdoors, a process generally known as hardening off. Begin by increasing the ventilation during the day in the greenhouse, after which the plants should be moved to a cold frame. Keep the windows closed at night for several days, then slowly increase the ventilation until the plants are continuously exposed to the outside air for a few days before planting out.

Watch the plants during hardening off. If the leaves turn blue or blotchy and growth stops you will need to decelerate the process.

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