Aquatic and Wetland Vascular Plants of the Northern Great Plains
1. Equisetaceae, the Horsetail Family
1. Equisetum L. -- Horsetail, scouring rush2. Equisetum fluviatile L. -- Water horsetail
Stems alike, annual, erect, to 1 m tall, shallowly 9- to 25-ridged, the ridges smooth; central cavity ca. 4/5 the stem diameter, the stem wall thin; small outermost cavities opposite the ridges of the stem, i.e., on the same radius; main stem sheaths 6-10 mm long, the teeth free, dark brown to black, 2-2.5 mm long. Branches none to many, rather regular when present, simple, ascending, 4- to 6-angled. Cones terminal on the main stem or occasionally on upper branches, blunt, long-stalked, deciduous, appearing Jun--Aug. Marginal or emergent in swamps, bogs and spring-fed marshes where water is fresh; frequent in n ND, otherwise uncommon; (Circumboreal, in N.Amer. s to PA, MN, NE and OR).
Previous Species -- Equisetum arvense L. -- Common horsetail
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