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Grafting 101

© Jojo Sigurgeirson

WHY ARE PLANTS GRAFTED?
Plants are grafted for many reasons. In fruit trees, different varieties are grafted onto each other so that multiple varieties can be grown on a single tree. Fruit trees are also grafted for the creation of a dwarf variety. Ornamental plants such as roses and tree peonies are often grafted for quality and hardiness.

Nearly all woody plants of "named" varieties ('Newton' Apple, 'Sexy Rexy' Rose) are propagated in this way, not by seeds. Of course it is also possible to propagate a named variety by taking cuttings and inducing them to root, but with fruit trees this is a lengthy process, and even then the percentage of successes is not high. They lose the advantage that the rootstock gave them, such as disease resistance, ability to tolerate certain adverse soil conditions, or ability to cause the resulting grafted tree to be smaller when mature ("dwarfing rootstock").

I had heard stories of people grafting herbaceous plants, even annuals, and decided to try this a few years ago. The resulting tomato was an interesting specimen, but hardly worth repeating. Marijuana growers occasionally graft highly-bred, intoxicating varieties onto seed plants with strong roots for mass hydroponic production. On the whole though, most grafting is done on woody plants.

WHAT ARE THE COMPONENTS OF A GRAFTED PLANT?
In grafted plants, there is the root stock and the top stock. This top stock is called a "scion". Sometimes a plant is grafted for root stock, stem qualities and top stock. This is fairly common in ornamental weeping trees, such as cherries, mulberries and birch. This way, the resulting plant can have hardy roots, interesting bark, and excellent weeping branches and flowers. So there is rootstock, interstem and scion.

As an example, an apple rootstock is simply another variety of apple tree, each variety usually indicated by a code like M-26 or P-22, which originally grew from a seed somewhere, was found to have something desirable as far as its roots were concerned, and is now itself propagated by a specialized nursery in one non-seed way or another ("clonal rootstock"). This tree is entirely capable of living on its own; if nothing were ever grafted onto it, it would grow into an apple tree, bloom, and bear apples, although the apples would not likely be of very good quality.

Thus we want the rootstock only for what its roots can do, and the scion only for the fruit that its branches and leaves will produce. When the two are joined, we will have a tree more desirable for our needs.