Swamp Horsetail, Water horsetail

Equisetum fluviatile

Physical Characteristics

Equisetum fluviatile is a PERENNIAL growing to 1.2 m (4ft). See above for USDA hardiness. It is hardy to UK zone 2. The seeds ripen from June to July. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist or wet soil and can grow in water.

Distribution

Arctic and temperate regions of Europe, including Britain, N. America and Asia.

Habitats

Pond; Bog Garden;

Edible Uses

Edible Parts: Root Shoots Stem Edible Uses: Strobil (the fertile shoots in spring) - cooked[2, 4, 85]. Used as an asparagus substitute, though it is neither palatable nor nutritious[4]. Caution is advised, see the notes above on toxicity. Roots - cooked[4, 85, 105]. The roots contain a nutritious starch[2]. Caution is advised, see the notes above on toxicity.

Medicinal Uses

Styptic Horsetails have an unusual chemistry compared to most other plants[238]. They are rich in silica, contain several alkaloids (including nicotine) and various minerals[238]. The plant is styptic[61]. The barren stems are used, they are most active when fresh but can also be dried and sometimes the ashes of the plant are used[4]. A decoction applied externally will stop the bleeding of wounds and promote healing[4].

Known Hazards

Large quantities of the plant can be toxic. This is because it contains the enzyme thiaminase[172], a substance that can rob the body of the vitamin B complex[65]. In small quantities this enzyme will do no harm to people eating an adequate diet that is rich in vitamin B, though large quantities can cause severe health problems. The enzyme is destroyed by heat or thorough drying, so cooking the plant will remove the thiaminase[172]. The plant also contains equisetic acid - see the notes on medicinal uses for more information[213].