Aerial stems lasting less than a year, occasionally overwintering in the southwestern United States, usually unbranched, 20--150 cm; lines of stomates single; ridges 10--32. Sheaths green, elongate, 7--15 × 3--9 mm; teeth 10--32, articulate and usually shed early, leaving dark rim on sheath. Cone apex rounded to apiculate with blunt tip; spores green, spheric. 2 n =216. Cones maturing in spring--early summer. Moist prairies, riverbanks, roadsides; 1530--3500 m; Alta., B.C., Man., Ont., Que., Sask.; Ariz., Ark., Calif., Colo., Idaho, Ill., Ind., Iowa, Kans., Mich., Minn., Mo., Mont., Nebr., Nev., N.Mex., N.Dak., Ohio, Okla., Oreg., S.Dak., Tex., Utah, Wash., Wis., Wyo.; n Mexico including Baja California. Schaffner named this species Equisetum kansanum because he applied the name E . laevigatum to what we now know is the hybrid E . × ferrissii . The coarser-stemmed, occasionally persistent forms in the southwestern United States have been called Equisetum funstonii .
General: Perennial rhizomatous with slender aerial stems, often flexuous to 75 cm tall, simple or verticillately branched at base, basal branches sterile. Leaves: No real leaves, stems annual, 20-30-ridged, ridges have transverse, sharply projecting bands of silica, hollow internodes with toothed sheaths narrowly funnelform to campanulate, green or with dark basal ring, teeth horny, blackish, incurved, especially with age. Sporangia: Strobili small, 1-2 cm long, obtuse or acute but not markedly apiculate at apex; greenish sporangia born in terminal cones. Ecology: Found in damp seeps, along streams and at the bottom of canyons from 3,000-8,000 ft (914-2438 m). Notes: Fairly common horsetail along streams in Arizona. Ethnobotany: Many medicinal uses, including: hair wash, contraceptive, for bladder ailments, for hemmoroids, high blood pressure, backaches, for lightning infections, lumbago, colds, to stimulate the kidneys, and as a wash for those parts of the body affected by poison ivy. Etymology: Equisetum is from equus, horse and seta, bristle, while laevigatum means smooth or slippery. Sources: Yatskievych and Windham 2008