Equisetum palustre, the marsh horsetail,^[2] is a perennial herbaceous pteridophyte belonging to the division of horsetails (Equisetopsida). It is widespread in cooler regions of North America and Eurasia.^[3][4]

Quick Facts Marsh horsetail, Conservation status ...

Marsh horsetail
Equisetum palustre
Conservation status
Secure  (NatureServe)
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Division:	Polypodiophyta
Class:	Polypodiopsida
Subclass:	Equisetidae
Order:	Equisetales
Family:	Equisetaceae
Genus:	Equisetum
Subgenus:	E. subg. Equisetum
Species:	E. palustre
Binomial name
Equisetum palustre L.
Synonyms[1]
Equisetum majus Garsault Equisetum braunii J.Milde

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Equisetum palustre has stems growing between 20-40 centimeters. The upright stems are usually scarcely branched with loose green leaf sheaths that have 5-10 narrow, dark teeth. The teeth are light at the edges. The lowest internode of the upright branches are much shorter than the leaf sheath of the stem.^[5]

The rough, furrowed stem is one to three mm in diameter with usually eight to ten ribs, in rare cases, four to 12. It contains whorled branches.^{[citation needed]}

The spores are spread by the wind (anemochory) and have four long ribbon-like structures attached to them. The spores sit on strobili which are rounded on the top. Marsh horsetails often form runners, with which they also can proliferate vegetatively.^[5]

Linnaeus was the first to describe marsh horsetail with the binomial Equisetum palustre in his Species Plantarum of 1753.^[6]

Equisetum palustre is green from spring to autumn and grows spores from June to September. It grows primarily in nutrient-rich wet meadows. It is found in Europe and the circumpolar region up to mountainous heights. Its distribution is declining.^{[citation needed]}

In Finland, it has benefited from human action and grows often in road and track sides, ditches and especially peat based fields and pastures.^[5]

A specific plant association in which E. palustre is found is the Juncus subnodulosus-Cirsium palustre fen-meadow.^[7]

Equisetum palustre is poisonous to mammals, most often reported as potentially fatal to horses, as it contains alkaloids palustrine and palustridiene, which destroy vitamin B₁. According to Wink, Equisetum Palustre also contains thiaminase enzymes. It's also known to contain lesser amounts of nicotine. Many thiaminases, however, are denatured by heat, and some sources refer Equisetum palustre safe to eat in moderate amounts when properly cooked.^{[8][9][10][11]} In Finland, it used to lower the production of dairy when cows would eat them in place of other preferable fodder.^[5]

• Marsh horsetail in Kythira