As noted earlier, propagation research is ongoing. The uses of grafting will no doubt increase as more is learned about the reasons for its current limitations. Some of the widely accepted information about grafting can be summarized as follows:
• Grafting can increase the winter hardiness of certain plants by providing them with a root system that is more tolerant of low temperatures.
• Replacing the root system with that of a more resistant species can permit the growth of plants normally susceptible to soil-borne pathogens.
• Trees girdled by animals, lawn mowers, or vandals can often be saved by bridge-grafting.
• A pistillate dioecious plant can have a scion from a staminate counterpart grafted to one of its branches to ensure the pollination needed for fruiting.
• Multiple cultivars can be grown on one established tree assuming all are compatible with it. Thus, it is possible to have rose bushes with several different-colored blooms on one plant, apple trees that bear four or five different kinds of apples, and the same with citrus fruits.
• Some hybrid plants grow more vigorously if removed from their own root system as seedlings and grafted onto another rootstock.
• The rootstock can greatly influence the subsequent growth of the scion after graft union. The effect may be one of dwarfing or acceleration, altered growth habit, increased or reduced flowering and fruiting, pest resistance, or hardiness.
•Not all plants graft and unite as easily as others. It is not a problem of incompatibility but of species variation. Also, some species graft more successfully by one technique than by another.
• Not all plants can be grafted. Generally, the closer the botanical relationship between the plants involved, the greater the probability of a successful graft. For example, grafting among members of the same clone is predictably successful; among different species of the same genus, some will graft and some will not; among different genera, grafting is highly improbable.