Dictionary of botanic terminology - index of names

Own-Roots versus Grafts: 
There is an endless debate about "own-root" versus "grafted/budded" plants. Depending on which book you read, or who you talk to. Own-roots plants are plants that are not grafted whose rootstock (the roots system) is the same type as the top of the plant. They are one variety from the top flower bud down to the last root. While a grafted plant, is a plant where the desired plant is grafted or budded onto a rootstock of a different type. The point where the desired variety and the rootstock meet is called the graft union (or bud union).
Don't confuse own-root plants with bare-root plants, the terms refer to different things. Plants are usually sold either bare-root (no soil around the roots) or potted in containers. Bare-root plants can be either own-root or grafted.
Grafting a small piece of stem or bud from the desired plant onto a vigorous other variety rootstock is a fast way to produce the desired variety. There are some good reasons to graft plants for some varieties. A vigorous rootstock can make a weaker variety grow well. Own root plants are usually smaller than grafted one in the beginning while grafts grow very rapidly. Some rare cacti for example are very difficult or extremely slow to grow from their own roots and only a few expert cactus enthusiasts attempt to cultivate them on their own root.. Many plant are sold as grafted plants, since it is more economical than selling own-root, but most of them are vigorous enough to grow well without grafting.
Unfortunately, there are some disadvantages to grafting, too. The graft will potentially be a weak spot for the lifetime of the plant, own-root plants have (usually) a much longer life than grafted ones. After some years, some grafted plants tends to form a knot at the graft union and the plant loses its vigour and must cease to grow. This is not a problem for own-root plants, since they lack the knobby graft union of grafted ones. Own root plants are also much truer to type than grafted ones.

Sometimes shoots will emerge from the rootstock. If the plant is grafted this shoot or sucker will be the same type of the rootstock, not the desired plant. When this happens with own-root plants, the shoot will be of the desired variety. With own-root plant you never have to bother with removing unwanted shoots of the rootstock variety. De-suckering is very important for grafted plants as without it the vigorous rootstock can take over and replace the original plant