Distribution
Afghanistan, Albania, Algeria, Austria, Belarus, Belgium, Bolivia, Bulgaria, Burundi, Cambodia, Colombia, Costa Rica, Cyprus, Denmark, Ecuador, El Salvador, Finland, France, Georgia, Germany, Greece, Guatemala, Haiti, Honduras, Hungary, Iceland, India, Iran, Iraq, Ireland, Italy, Kenya, Morocco, Netherlands, Norway, Peru, Poland, Portugal, Romania, Rwanda, Spain, Sweden, Switzerland, Taiwan, Tanzania, Tunisia, Turkey, Uganda, Ukraine, Venezuela

Native to: Afghanistan, Alabama, Alaska, Albania, Algeria, Altay, Arizona, Arkansas, Austria, Azores, Baleares, Baltic States, Belarus, Belgium, Bolivia, British Columbia, Bulgaria, Burundi, California, Cambodia, Canary Is., Central European Rus, China North-Central, China South-Central, China Southeast, Colombia, Connecticut, Corse, Costa Rica, Cyprus, Czechoslovakia, Delaware, Denmark, District of Columbia, East Aegean Is., East European Russia, East Himalaya, Ecuador, El Salvador, Finland, Florida, France, Free State, Føroyar, Georgia, Germany, Great Britain, Greece, Guatemala, Haiti, Honduras, Hungary, Iceland, Idaho, Illinois, India, Indiana, Iowa, Iran, Iraq, Ireland, Italy, Kansas, Kentucky, Kenya, Krasnoyarsk, Kriti, Krym, Leeward Is., Louisiana, Madeira, Maine, Manchuria, Manitoba, Maryland, Masachusettes, Mexican Pacific Is., Mexico Central, Mexico Gulf, Mexico Northeast, Mexico Northwest, Mexico Southeast, Mexico Southwest, Michigan, Minnesota, Mississippi, Missouri, Montana, Morocco, Nebraska, Netherlands, New Brunswick, New Hampshire, New Jersey, New York, Newfoundland, North Carolina, North Caucasus, North European Russi, Northern Provinces, Northwest European R, Norway, Nova Scotia, Ohio, Oklahoma, Ontario, Oregon, Palestine, Pennsylvania, Peru, Poland, Portugal, Prince Edward I., Québec, Rhode I., Romania, Rwanda, Sardegna, Sicilia, South Carolina, South European Russi, Spain, Svalbard, Sweden, Switzerland, Taiwan, Tanzania, Tennessee, Texas, Tibet, Transcaucasus, Tunisia, Turkey, Turkey-in-Europe, Uganda, Ukraine, Venezuela, Vermont, Virginia, Washington, West Himalaya, West Siberia, West Virginia, Wisconsin, Yugoslavia, Zaïre, Zimbabwe.

Introduced into: Amsterdam-St.Paul Is, Cape Provinces, Colorado, Falkland Is., Hawaii, Irkutsk, Madagascar, Marion-Prince Edward, Mauritius, New South Wales, New Zealand North, New Zealand South, St.Helena, Tristan da Cunha, Victoria.

Herbs, perennial, 4-13 dm. Rhizomes short -branched, forming distinct, often large clumps. Culms erect, terete, 1-2.5 mm diam. at top of sheaths. Cataphylls several. Leaves: blade absent. Inflorescences lateral, compound dichasia, many flowered; primary bract erect, terete, extending well beyond dichasium. Flowers: tepals tan or darker, usually with greenish midstripe, lanceolate, 1.9-3.5 mm; inner slightly shorter; stamens 3, filaments 0.5-0.8 mm, anthers 0.5-0.8 mm; style 0.2 mm. Capsules greenish tan or darker, 3-locular, broadly ellipsoid to oblate, 1.5-3.2 mm. Seeds amber, (0.3-)0.4-0.5 mm. 2n = 40, 42.
Flowering summer, fruiting summer-fall. Swamps and their edges, marshes, moist meadows, and moist or saturated soils, often conspicuous in pasture meadows where it is shunned by grazing animals.