In biology, stolons (from Latin stolō "branch") are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external skeletons.
In botany, stolons are stems which grow at the soil surface or just below ground that form adventitious roots at the nodes, and new plants from the buds. Stolons are often called runners. Rhizomes, in contrast, are root-like stems that may either grow horizontally at the soil surface or in other orientations underground. Thus, not all horizontal stems are called stolons. Plants with stolons are called stoloniferous.
A stolon is a plant propagation strategy and the complex of individuals formed by a mother plant and all its clones produced from stolons form a single genetic individual, a genet.
Stolons may or may not have long internodes. The leaves along the stolon are usually very small, but in a few cases such as Stachys sylvatica are normal in size.
Stolons arise from the base of the plant. In strawberries the base is above the soil surface; in many bulb-forming species and plants with rhizomes, the stolons remain underground and form shoots that rise to the surface at the ends or from the nodes. The nodes of the stolons produce roots, often all around the node and hormones produced by the roots cause the stolon to initiate shoots with normal leaves. Typically after the formation of the new plant the stolon dies away in a year or two, while rhizomes persist normally for many years or for the life of the plant, adding more length each year to the ends with active growth. The horizontal growth of stolons results from the interplay of different hormones produced at the growing point and hormones from the main plant, with some studies showing that stolon and rhizome growth are affected by the amount of shady light the plant receives with increased production and branching from plants exposed to mixed shade and sun, while plants in all day sun or all shade produce fewer stolons.