INTRO TO ROOTSTOCKS
In grafting a rootstock refers to a plant, sometimes just a stump, which already has an established, healthy root system onto which a cutting or a bud from another plant is grafted.
The rootstock may be a different species from the scion, but as a rule it should be closely related, for example, many commercial pears are grown on quince rootstock. When it is difficult to match a plant to the soil in a certain field or orchard, growers may graft a scion onto a rootstock that is compatible with the soil.
It may then be convenient to plant a range of ungrafted rootstocks to see which suit the growing conditions best; the fruiting characteristics of the scion may be considered later, once the most successful rootstock has been identified.
CHOOSING A VARIETY
For a graft to be successful there must be compatibility between the rootstock and the scion. Different rootstock have different effects on the growth of the scion. Average total tree size, vigor, early bearing, volume of fruit, and soil tolerances are only some of the features of rootstocks. Depending on your soil, environment, and goals different rootstocks may be better suited than others. It is important to choose the right rootstock for you area.