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.

Description

The green stems grow tall and 2–8 mm thick. The leaf sheaths are narrow, with 15–20 black-tipped teeth. Many, but not all, stems also have whorls of short ascending and spreading branches 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.

The water horsetail has one of the largest central hollows of the horsetails, with 80% of the stem diameter typically being hollow.

thumb|240px|none|Equisetum fluviatile – a broken stem with the central hollow exposed

The stems readily pull apart at the joints, and both fertile and sterile stems look alike.

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 long.

Reproduction

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.

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.

Uses

Domestic

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.

Early spring shoots were eaten. Poorer Roman classes at times ate them as a vegetable, despite not being very palatable or nutritious.

References

  • Equisetum fluviatile Water Horsetail at Boundary Waters Canoe Area Wilderness
  • Equisetum fluviatile at World of Equisetum
  • Equisetetum fluviatilis