A stolon is a specialized type of plant stem which the plant uses to propagate itself. Stolons are capable of budding to produce clones of the parent plant, thereby allowing the plant to colonize an area of ground with its young. One of the most classic examples of a stolon can be found on the strawberry, a plant which utilizes this method of propagation very effectively. Many grasses also colonize regions in this way, as do some aquatic plants.

Stolons look slightly different than regular stems, and they typically have distinctive nodes at which new growth can develop. They usually run horizontally, and they may be located above or below ground, depending on the species of plant involved. In some cases, stolons grow upright and later bend over or droop down to allow the nodes to come into contact with the ground so that the plant can bud and produce an offspring.

Initially, the developing clone on the stolon relies on the parent plant for nutrition. Over time, the plant will root itself and become independent, so that it no longer requires nutrition from the stolon. It may also put out stolons of its own, thereby increasing the size of the plant colony. The network of specialized stems can quickly cover the ground, creating a dense mat of young plants and eliminating competition from other plants.

These unique stems are sometimes referred to as “runners,” because they run along the ground. In some cases, the development of a stolon is desirable, and gardeners may be pleased to see them appear. In other instances, however, these growths may be a problem, especially in the case of invasive plants, because stolons make it very difficult to totally eradicate a plant from the garden. Leaving even a single specimen in place will allow the plant to propagate with stolons, covering the ground all over again.

One disadvantage of relying on stolons for plant propagation is that because the plants are clones of the original plant, they are all susceptible to the same problems. If the parent plant is susceptible to a particular disease or infection, for example, all of the plants produced by stolons will be as well, which means that the plant can be quickly wiped out. For this reason, it's a good idea to grow several different parent plants, and to periodically introduce new plants, to keep genetic diversity high and prevent the loss of a desired crop or ornamental plant.