Equisetum hyemale, commonly known as rough horsetail, scouring rush, scouringrush horsetail and in South Africa as snake grass, is a perennial herb in the fern Division Pteridophyta. It is a native plant throughout the Holarctic Kingdom, found in North America, Europe, and northern Asia.
In nature Equisetum hyemale grows in mesic (reliably moist) habitats, often in sandy or gravelly areas. It grows from between sea level to 2,530 metres (8,300 ft) in elevation.
It is primarily found in wetlands, and in riparian zones of rivers and streams where it can withstand seasonal flooding. It is also found around springs and seeps, and can indicate their presence when not flowing. Other habitats include moist forest and woodland openings, lake and pond shores, ditches, and marshes and swamps.
Equisetum hyemale has vertical jointed reed-like stalks of medium to dark green. The hollow stems are up to 3 feet (0.91 m) in height. The stems are not branched. The stems themselves have conspicuous ridges, which are impregnated with silica. This makes the ridges feel rough and harsh.
The tiny leaves are joined together around the stem, forming a narrow black-green band or sheath at each joint. Like other ferns and their relatives, the plant reproduces by spores and does not produce flowers or seeds.
The stems are generally deciduous in cold climates, and remain during winter in warmer climates. It forms dense spreading colonies, in full to partial sun.
Equisetum hyemale subsp. affine — endemic to North America.