Equisetum laevigatum A. Braun

Smooth horsetail

Like all horsetails, smooth scouring rush prefers moist soil.

Identification:

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.

Habitats: Moist sandy or gravelly soils, such as sandy shores, roadsides, meadows, and prairies; with partial or full sunlight.

Edibility: Poisonous. 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:

Older scientific or horticultural names

Equisetum laevigatum description by Thomas H. Kent, not updated.

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