CLONAL DISTANCE. “Tillers, corms, bulbs, rhizomes, and tubers are usually produced relatively close to the parent plant. In contrast, stolons, runners, and bulbils usually result in ramets located at further distances from the parent plant. This variation gives rise to different levels of clonal aggregation within populations and has led to the identification of two contrasting clonal strategies that differ in the degree of intermingling of clones.”
http://www.pnas.org/content/112/29/8859.full