Equisetum (horsetail)

Equisetum

Horsetail

Kingdom	Plantae	Plants, but not fungi, lichens, or algae
Subkingdom	Tracheobionta	Vascular plants—plants with a “circulatory system” for delivering water and nutrients
Division	Equisetophyta	Horsetails, which date back to the Devonian era
Class	Equisetopsida	Horsetails, spore-bearing plants related to ferns
Order	Equisetales	Living horsetails (most are extinct)
Family	Equisetaceae	Living horsetails
Genus	Equisetum	From equus, horse; and seta, bristle

About plant names...

Horsetails are an ancient group of plants, little changed over 300 million years. The genus Equisetum means “horse bristles,” and refers to the plant’s unusually high levels of silica, which make it abrasive enough to serve for scouring, sanding, or polishing. Although Equisetum includes all the now-living relatives of these plants, extinct relatives reached 100' (30 m) in height as far back as the Carboniferous era.

Identification: For excellent comparison photos, see sophy.u-3mrs.fr.

Here are comparisons among the horsetails we have so far:

horsetail (Equisetum) · Equisetum variegatum, variegated horsetail. · 8/21/2003 · Chandos Lake, Ontario, Canada · By Janet Novak

	*Equisetum arvense*	*Equisetum fluviatile*	*Equisetum hyemale*
Common Name	field horsetail	water horsetail	rough horsetail
Leaves	Photo by Enrico Blasutto.	Tiny black scale leaves surround each segment of the stem. Cropped from a photo by Luc Viatour.
Stem	Fertile stems, which have no branches, are up to 12" (30 cm) high; sterile stems up to 24" (60 cm), multiply branched, with upward-pointing needle-like branches.	12-48" (30-121 cm) high, stems hollow, easily squeezed, usu. about ¼" (6.3 mm) in diameter. Smoother and hollower than other horsetails.
Fruit	Fertile stems have cones 1-1½" (2.5-3.8 cm) long in the spring. Photo by Kristian Peters.	Cone about 1" (2.5 cm) long, yellowish-green. Photo by joelpk@flickr.
Range/ Zones			USDA Zones: 4-9
Habitats	Fields, woods, marshes, roadsides, especially damp areas in partial shade	Ponds, marshes, slow-moving water
Type	Wild	Wild	Wild
Occurrence		Common, sometimes considered invasive

Equisetum description by Thomas H. Kent, last updated 16 Sep 2020.

(Equisetum) · 5/2/2010 · Nashua River Rail Trail, Groton Center, Groton, MA
≈ 10 × 14" (26 × 35 cm) Species not yet identified