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Equisetum hyemale (rough horsetail [2]) is an evergreen perennial herbaceous pteridophyte in the horsetail family Equisetaceae native to Eurasia and Greenland. It was formerly widely treated in a broader sense including a subspecies (subsp. affine ) in North America, but this is now treated as a separate species, Equisetum praealtum .
Equisetum (/ ˌ ɛ k w ɪ ˈ s iː t əm /; horsetail) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. [2]Equisetum is a "living fossil", the only living genus of the entire subclass Equisetidae, which for over 100 million years was much more diverse and dominated the understorey of late Paleozoic forests.
The plant is well identifiable from the 3-6 reddish brown leaf sheaths or "teeth". [1] [3] The fertile stems are shorter than the others; on these develop the cones that bear the spore casings or strobili. [1] The leaves develop on the fertile stems and the stems lengthen; then the cones open to release their spores. The cones then drop off.
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Equisetum arvense, the field horsetail or common horsetail, is an herbaceous perennial plant in the Equisetidae (horsetails) sub-class, native throughout the arctic and temperate regions of the Northern Hemisphere. It has separate sterile non-reproductive and fertile spore-bearing stems growing from a perennial underground rhizomatous stem system.
The green stems grow 50–150 cm tall and 2–8 mm thick. The leaf sheaths are narrow, with 15-20 black-tipped teeth. [2] Many, but not all, stems also have whorls of short ascending and spreading branches 1–5 cm long, with the longest branches on the lower middle of the stem.
Equisetum praealtum, [1] the scouringrush horsetail, [2] is a species of Equisetum (horsetail) native to North America and northeastern Asia. [1] It was formerly widely treated as a subspecies or variety of the European and west Asian species Equisetum hyemale (rough horsetail), and still is by some authorities.
Equisetum telmateia, the great horsetail, is a species of Equisetum (horsetail) native to Europe, western Asia and northwest Africa. [ 2 ] [ 3 ] It was formerly widely treated in a broader sense including a subspecies (subsp. braunii ) in western North America, but this is now treated as a separate species, Equisetum braunii .