''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 The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

and

Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...

, usually in freshwater wetland areas. It is known primarily from the Atlantic coastal plain from

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

Massachusetts Massachusetts ( ; ), officially the Commonwealth of Massachusetts, is a U.S. state, state in the New England region of the Northeastern United States. It borders the Atlantic Ocean and the Gulf of Maine to its east, Connecticut and Rhode ...

, and the Great Lakes region, with scattered populations elsewhere.Flora of North America v 23 p 120
/ref> ''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 ''Equisetum'' (; horsetail) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. ''Equisetum'' is a "living fossil", the only living genus of the entire subclass Equisetidae, which ...

''. The two species can be distinguished by the length of the

perianth The perianth (perigonium, perigon or perigone in monocots) is the non-reproductive part of the flower. It is a structure that forms an envelope surrounding the sexual organs, consisting of the calyx (sepals) and the corolla (petals) or tepal ...

bristles A bristle is a stiff hair or feather (natural or artificial), either on an animal, such as a pig, a plant, or on a tool such as a brush or broom. Synthetic types Synthetic materials such as nylon are also used to make bristles in items such as b ...

subtending the

achenes An achene (; ), also sometimes called akene and occasionally achenium or achenocarp, is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate (formed from one carpel) and indehiscent (they do not open ...

.Elliott, Stephen. Sketch of the Botany of South-Carolina and Georgia 1(1): 79. 1816.

References

equisetoides Flora of the United States Flora of Ontario Plants described in 1816 Flora without expected TNC conservation status {{Cyperaceae-stub