|Photosynthetic summer foliage|
Equisetum arvense, the Field Horsetail or Common Horsetail, is a herbaceous perennial plant, 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 fertile stems are produced in early spring and are non-photosynthetic, while the green sterile stems start to grow after the fertile stems have wilted, and persist through the summer until the first autumn frosts.
The sterile stems are 10–90 cm tall and 3–5 mm diameter, with jointed segments around 2–5 cm long with whorls of side shoots at the segment joints; the side shoots have a diameter of about 1 mm. Some stems can have as many as 20 segments. The fertile stems are succulent-textured, off-white, 10–25 cm tall and 3–5 mm diameter, with 4–8 whorls of brown scale leaves, and an apical brown spore cone 10–40 mm long and 4–9 mm broad.
The specific name arvense is derived from the Latin arvensis, meaning "from the meadow, field or grassland."
The plant contains several substances which can be used medicinally. It is rich in the minerals silicon (10%), potassium, and calcium. The buds are eaten as a vegetable in Japan and Korea in spring time. All other Equisetum species are toxic.
In polluted conditions, it may synthesize nicotine. Externally it was traditionally used for chilblains and wounds. It was also once used to polish pewter and wood (gaining the name pewterwort) and to strengthen fingernails. It is also an abrasive. It was used by Hurdy-Gurdy players to dress the wheels of their instruments by removing resin build up.
It is used in biodynamic farming to make the "silica" soil preparation.[clarification needed] (BD 508) Equisetum in particular is used because silicon reduces the effects of excessive water around plants that would lead to fungus. It is the high percentage of silica in the plant that works on lowering the impact of moisture.
Invasive species 
Equisetum arvense was introduced into New Zealand in the 1920s and has been classed as an invasive species since the mid-1990s. It is listed on the National Pest Plant Accord preventing its sale, spread and cultivation.
- Hyde, H. A., Wade, A. E., & Harrison, S. G. (1978). Welsh Ferns. National Museum of Wales ISBN 0-7200-0210-9.
- Flora of North America: Equisetum arvense
- Bebbington, A. "Toxicity of Equisetum to Horses". omafra.gov. Retrieved 1 December 2010.
- Howard, Michael. Traditional Folk Remedies (Century, 1987); p.159-160
- La Vielleuse Habile, Jean-Francois Bouin, 1761, page 19.
- Kearny, Peter. "Bio Dynamic Prep 508". Bio Dynamic Prep 208. City Food Growers. Retrieved June 2011.
- Howell, Clayson (May 2008). Consolidated list of environmental weeds in New Zealand. DRDS292. Wellington: Department of Conservation. ISBN 978-0-478-14413-0. Retrieved 2009-05-06.
|Wikimedia Commons has media related to: Equisetum arvense|
- E. arvense at Germplasm Resources Information Network (GRIN)
- Une entreprise en procès pour avoir commercialisé de la prêle (French)
- Horsetail at Medline
- Field Horsetail at Biosecurity New Zealand
- Washington Native Plant Society