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Equisetum laevigatum

Smooth horsetail

KingdomPlantaePlants, but not fungi, lichens, or algae
SubkingdomTracheobiontaVascular plants—plants with a “circulatory system” for delivering water and nutrients
DivisionEquisetophytaHorsetails, which date back to the Devonian era
ClassEquisetopsidaHorsetails, spore-bearing plants related to ferns
OrderEquisetalesLiving horsetails (most are extinct)
FamilyEquisetaceaeLiving horsetails
GenusEquisetumFrom equus, horse; and seta, bristle

About plant names...

Like all horsetails, smooth scouring rush prefers moist soil. It favors sandy or gravelly soils, such as sandy shores, roadsides, meadows, and prairies; with partial or full sunlight.

Plants: Plants are 8-60" (20-152 cm) tall, with smooth stems, rarely evergreen. Stems are about ¼" (6.3 mm) in diameter at the base, with 10-32 ridges parallel to the stem. Sterile stems are usually unbranched, but occasion­ally have stubby branches. In cross section, the stem has a central hollow area about ¾ the width of the stem. Fertile and sterile stems look very similar, except that fertile stems are tipped by a blunt-tipped “cone” that is ½-1" (1.3-2.5 cm) long.

See Equisetum for a comparison chart.

Leaves: Leaves are tiny and non-photosynthetic, occuring in sheaths around the stems, with 10-32 sharp black teeth around the top of each sheath. Sheaths are about ¼" (8.5 mm) long, usually green, sometimes turning brown. The teeth don’t persist for very long, leaving a thin dark ring around the top of the sheath.

Fruits: “Cones” (strobili) are ⅜-⅞" (1-2.5 cm) long, ellipsoid, and ¼-⅜" (7-10 mm) in diameter. They are blunt-tipped, sometimes with a tiny point.

Edibility: Poisonous. Skull & Crossbones Harmless in small quantities, but in larger amounts, it destroys vitamin B1.

Medical: Although used as herbal remedies for a wide variety of ailments over time, horsetails contain thiaminase, which breaks down thimaine (vitamin B1), causing a vareity of toxic symptoms in animals.

Online References:

Equisetum laevigatum on Wildflowers, Ferns & Trees of Colorado, New Mexico, Arizona, and Utah

Equisetum laevigatum at Minnesota Wildflowers

Equisetum laevigatum on inside.ewu.edu (great photos)

Equisetum laevigatum on michiganflora.net

Equisetum laevigatum on Wildflowers of the United States

Equisetum laevigatum on www.deltacountyindependent.com

Equisetum laevigatum on ferns.brit.org


Equisetum laevigatum description by Thomas H. Kent, last updated 30 Nov 2020.

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Equisetum laevigatum (smooth horsetail)

5/25/2008 · Memphis, Ten­nes­see · By Tim Chandler