The term "root stock" refers to the plant that provides the roots for another plant (called the scion) that is grafted onto it. Root stock is used to propagate plants that are difficult to grow from cuttings or seeds, such as some pines and dwarf cultivars. Root stock can also influence the growth rate, disease resistance, and hardiness of the scion. For bonsai purposes, root stock should be grafted as low as possible to avoid unsightly unions and mismatches in bark characteristics. Ideally, the graft should be buried at the soil line to create the illusion of a single plant.