horsetail

or scouring rush

Any of the 15 species of rushlike (see rush), conspicuously segmented, perennial herbaceous plants that make up the genus Equisetum. They grow in moist, rich soils everywhere except Australasia. Some are evergreen; others send up new shoots every year. The stems contain abundant silicate minerals and other minerals. The leaves are merely sheaths that encircle the shoots. An ancient plant, the horsetail's relatives date to the Carboniferous Period. The common horsetail (E. arvense) is widespread along streambanks and in meadows in North America and Eurasia. Though poisonous to livestock, horsetails are used in folk medicines. Because of their abrasive stems, some species have been used in polishing tools.

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