Equisetum fluviatile
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Equisetum fluviatile, the water horsetail or swamp horsetail, is a vascular plant in the horsetail family Equisetaceae. It is a perennial herbaceous pteridophyte that reproduces using spores.
DescriptionEdit
The green stems grow 50–150 cm tall and 2–8 mm thick. The leaf sheaths are narrow, with 15-20 black-tipped teeth.<ref name="Piirainen">Template:Cite book</ref> 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. The side branches are slender, dark green, and have 1–8 nodes with a whorl of five scale leaves at each node.Template:Citation needed
The water horsetail has one of the largest central hollows of the horsetails, with 80% of the stem diameter typically being hollow.<ref name="web.archive.org">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The stems readily pull apart at the joints, and both fertile and sterile stems look alike.Template:Citation needed
The water horsetail is most often confused with the marsh horsetail E. palustre, which has rougher stems with fewer (4–8) stem ridges with a smaller hollow in the stem centre, and longer spore cones 2–4 cm long.Template:Citation needed
ReproductionEdit
The water horsetail reproduces both by spores and vegetatively by rhizomes. It primarily reproduces by vegetative means, with the majority of shoots arising from rhizomes. Spores are produced in sporangia in blunt-tipped cones at the tips of some stems.<ref name="Piirainen" /><ref name="web.archive.org" /> The spore cones are yellowish-green, 2,5 cm long.<ref name="web.archive.org" />
Distribution and habitatEdit
The water horsetail ranges throughout the temperate Northern Hemisphere, from Eurasia south to central Spain, Italy, the Caucasus, China, Korea and Japan, and in North America from the Aleutian Islands to Newfoundland, south to Oregon, Idaho, northwest Montana, northeast Wyoming, West Virginia and Virginia.Template:Citation needed
It commonly grows in dense colonies along freshwater shorelines or in shallow water in ponds, swamps, ditches, and other sluggish or still waters with mud bottoms.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
This horsetail is sometimes seen as an invasive species because it is very hardy and tends to overwhelm other garden plants unless it is contained. When planting, it is best to plant them with the rhizome in a container.Template:Citation needed
UsesEdit
DomesticEdit
The water horsetail has historically been used by both Europeans and Native Americans for scouring, sanding, and filing because of the high silica content in the stems.Template:Citation needed
Early spring shoots were eaten. Poorer Roman classes at times ate them as a vegetable, despite not being very palatable or nutritious.<ref name="web.archive.org" />
Medical and agriculturalEdit
Medically it was used by the ancient Greeks and Romans to stop bleeding and treat kidney ailments, ulcers, and tuberculosis, and by the ancient Chinese to treat superficial visual obstructions. Template:Citation needed
According to Carl Linnaeus, reindeer, which refuse ordinary hay, will eat this horsetail, which is juicy, and that it is cut as fodder in the north of Sweden for cows, with a view to increasing their milk yield, but that horses will not touch it.<ref name="web.archive.org" /> It has also been used as a feed for livestock in Finland and is considered valuable, even better than many cultivated hays.<ref name="Piirainen" />
Horsetails absorb heavy metals from the soil, and are often used in bioassays for metals.Template:Citation needed
TaxonomyEdit
Linnaeus was the first to describe water horsetail with the binomial Equisetum sylvaticum in his Species Plantarum of 1753. In the same work, he also described the unbranched form of the plant as a separate species, E. limosum.<ref>Template:Cite book</ref>