Equisetum hyemale L.

Common Scouring Rush

© DETenaglia

Family - Equisetaceae

Habit - Rhizomatous perennial forb, with sporangia aggregated into dense strobili.

Stems - Monomorphic, erect, to 1.6 m, persistent for more than 1 year, green, hollow, roughened, 14-50-ridged, jointed at nodes, unbranched or sometimes irregularly branched at some nodes.

	Stems and nodes.
© DETenaglia

	Stem, lateral section near node.
© SRTurner

Leaves - Whorled, highly reduced, fused for part of their length to form a collarlike sheath around the stem. Sheath with a broad dark band near the base, usually also with a white band in the middle and a thin, dark band at the tip, with small teeth along the tip of the sheath, these sometimes persistent at maturity, narrowly triangular, attenuate, black.

Sporangia - Saclike, in whorls on the underside of highly modified leaves (sporangiophores), these peltate, hexagonal in surface view, and aggregated in dense whorls into conelike strobili occurring at the stem or branch tips. Strobili 1.0-2.5 cm long, the tips rounded to an abrupt, sharp point.

	Strobili.
© DETenaglia

	Strobilus.
© SRTurner

Spores - Globose, 35-70 μm in diameter, green, each with 4 spirally curled, white filaments (elaters) that uncurl and spread apart upon drying, aiding in dispersal. Gametophytes green, growing at or near the soil surface, disk- to cushion-shaped, irregularly lobed.

	Plant shedding spores.
© SRTurner

Flowering - March - August.

Habitat - Ditches, roadsides, moist to wet ground, railroad embankments.

Origin - Native to the U.S.

Lookalikes - E. laevigatum.

Other info. - This interesting species is common throughout Missouri and occurs from coast to coast across the continental U.S. Of the three species of Equisetum in Missouri, this one is by far the most common. It is easily recognized by general appearance, although the less common E. laevigatum can appear similar. That species has stems which are smooth and leaf sheaths with only a thin dark band near the top. Under favorable conditions, E. hyemale is an aggressive species and can form large, dense colonies.

The common moniker "scouring rush" referred to the historical use of the stems to scrub and polish dishes and silverware. The stems are still used by musicians to polish the reeds of woodwind instruments. The abrasive quality of the stems is due to their content of silica (silicon dioxide, the substance of which sand is composed).

The genus name Equisetum refers to another common name, "horsetail," which is most commonly applied to other members of the genus having whorled leaves with a bushy appearance. The species name hyemale means "winter." Equisetum is the only surviving genus in an ancient class of plants which flourished on the earth over 200 million years ago, contemporaneous with dinosaurs and prior to the emergence of flowering plants.

Photographs taken in Gainesville, FL., 7-21-02 (DETenaglia); also along the Katy Trail southeast of Dutzow, Warren County, MO, 6-21-2010, 6-30-2019, and 4-3-2022 (SRTurner).