Horsetail

Horsetail and scouring rush are the common names of approximately 35 living species and hybrids and numerous fossil species of the plant genus Equiselum. They belong to the order Equisetales, family Equisetaceae. Horsetails grow primarily in swampy places worldwide except in Australia and New Zealand. The hollow, rigged stem in distinctly jointed and rich in silica, giving it a gritty texture. The leaves are reduced to small sheaths clasping each joints. Horsetails are perennial and reproduce by abundant rhizomes and by spores.

E. arvense, the common horsetail, grows to 60 cm (12 in) and is one of the most widely distributed species along stream banks and meadows of North America and Eurosia. The stem of E. hyemale, the common  scouring rush , of Europe and North America, grow to 1.5 m (5 ft) and contain so much silica that are used by Europe and cabinetmakers to polish furniture and wooden floors. The largest horsetails are E. myriochaelum and E. giganteum, found from Mexico to South America. They commonly grow to 5 m (16 ft), but specimens up to 10 m (32 ft) have been reported.

Fossil speciment of Equisetum have been found dating from Jurassic Period. Horsetails are closely related to Calamitales, large, treellike giant horsetail of the coal bearing Carboniferous Period. Some horsetail species are use as food like asparagus or pickled, or the whole plant is ground and made into mush. Horsetails are also used as fodder for livestock, but poisoning can occur.