What is grafting?

Grafting is the act of joining two plants together. The upper part of the graft (the scion) becomes the top of the plant; the lower portion becomes the root system or part of the trunk. Although grafting usually refers to joining only two plants, it may be a combination of several. A third plant added between two others becomes the trunk or a portion of it. This is called an interstem. Multiple grafts may produce an apple tree with several varieties or a rose-of-Sharon shrub with several different colors of flowers. 

Why Graft?

But why should gardeners graft?  Some cultivars (varieties) of plants do not come true from seeds. Others are difficult or impossible to reproduce from cuttings or other propagation techniques. Grafting is a way to change a large tree from an old to a new variety. It is also a method of using a root system better adapted to soil or climate than that produced naturally by an ungrafted plant. By using special understocks or interstems, grafting is a way to produce dwarf plants.

Which plants can be grafted?

Not all plants can be grafted. Generally, only plants closely related botanically form a good graft union. Grafting is not a means of developing new varieties. The stock and scion must be compatible. Incompatible grafts may not form a union, or the union may be weak. A poor union results in plants that grow poorly, break off or eventually die. The compatibility of plants has been determined through many years of trial. There is no other way to determine whether or not two plants will produce a good graft union. This publication will help you make a decision about the possibility.

Most varieties of a particular fruit or flowering species are interchangeable and can be grafted. Because of differences in vigor, some are better able to support others as understocks. For example, although a union is possible, sour cherry is not a good understock for sweet cherry. Sweet cherry is more commonly grafted onto Mazzard (Prunus avium) or Mahaleb (P. mahaleb) seedlings.

Plants of the same botanical genus and species can usually be grafted even though they are a different variety. Plants with the same genus but of a different species often can be grafted. But the result may be weak or short-lived, or they may not unite at all.

Plants of different genera are less successfully grafted, although there are some cases where this is possible. For example, quince, genus Cydonia, may be used as a dwarfing rootstock for pear, genus Pyrus.

Plants of different families cannot be grafted successfully. Although it has been reported that relatively short-lived grafts of herbaceous plants of different families have been made, there is no successful practice for commercial or home grafting of woody plants of different families.

It is sometimes believed that two plants can be made into a genetically different plant by the process of grafting. However, there is no basis for this idea. Although there are cases where a different type of shoot develops from the graft union, this is the result of a chimera, a type of mutation. This is not a true intermingling of the genetic structure of two different plants as occurs in seed-produced hybrids.

When is the best time to graft?

Most grafting is done in late winter or early spring before new growth begins. The best time is after the chance of severe cold has passed but well before hot weather arrives. Scion wood may be collected during the winter. Store it in a cold, moist place at temperatures close to 34 degrees Fahrenheit. At home, a few scions could be stored in a plastic bag in the refrigerator with moist paper towels, or they could be dipped in paraffin so they retain moisture.

Two main grafting techniques

Grafting techniques can be divided into two basic types, which are largely determined by the size of the understock. In some cases, a graft may be made to join a scion and understock of nearly equal size. The other type attaches a small scion to a much larger understock. In this case, several scions may be attached to the understock as in cleft or bark grafting.
 

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