What is the term for stems that run horizontally above ground?

The term for stems that run horizontally above ground is stolons. Stolons are specialized structures that allow a plant to propagate vegetatively by extending a stem along the soil surface. These stems can produce new plants at various nodes, which can root and grow into independent individuals, effectively allowing the plant to spread and establish new colonies.

In contrast, bulbs refer to underground storage organs that consist of a short stem surrounded by fleshy scales or leaves. Rhizomes, on the other hand, are similar to stolons but grow horizontally underground, acting as a means for a plant to spread nutrition and produce new shoots from below the soil surface. Corms are also underground storage organs, like bulbs, but are solid and typically do not have the same vegetative propagation capability as stolons do. Thus, when identifying stems that run horizontally above ground specifically, stolons is the most accurate term.