Eleocharis equisetoides, with common names including horsetail spike-rush, jointed spike-rush, spikesedge, and knotted spike-rush, is a plant species native to the United States and Ontario, usually in freshwater wetland areas. It is known primarily from the Atlantic coastal plain from Texas to Massachusetts, and the Great Lakes region, with scattered populations elsewhere.Flora of North America v 23 p 120Biota of North America Program 2013 county distribution mapKew World Checklist of Selected Plant Families
Eleocharis equisetoides and the related E. interstincta have hollow stems with complete transverse septa. This gives them a jointed appearance superficially resembling the stems of some species of Equisetum. The two species can be distinguished by the length of the perianth bristles subtending the achenes.Torrey, John. Annals of the Lyceum of Natural History of New York 3: 296. 1836.Elliott, Stephen. Sketch of the Botany of South-Carolina and Georgia 1(1): 79. 1816.
References