Smooth Horsetail

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 .

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.

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.

Cones maturing in spring--early summer. Moist prairies, riverbanks, roadsides; 1530--3500m.

Equisetum funstonii A.A. Eaton, E. kansanum J.H. Schaffner

Equisetum laevigatum is a rush-like perennial that rises from an underground rootstock structure. Normally the plant dies back over the winter, but some populations in the southwestern USA have individuals that can overwinter. The plant manifests jointed rough stems which are closed at the joints. The stem roughness are a result of inclusions of silica. Each stem exhibits longitudinal grooves that run vertically. Each joint has a sheath which is a minute pointed leaf-like structure. The species usually occurs along moist drainages in sandy and gravelly substrates.

The narrow green stems can attain heights ranging from 30 to 150 centimeters. The stems are generally unbranched and are capped with rounded cone-shaped sporangia. Stomata occur in single lines; moreover, the spherical spores of this species are green.

The appearance of this taxon is very similar to E. hyemale; moreover, The geometric arrangement of silica-tuberles at the shoot surface may be the best means to differentiate these two species.

Equisetum laevigatum is broadly distributed across North America in including the entire western USA and Great Plains. The southeastern USA and New England are excluded from the range. In Canada, the taxon is widely found in the entirety of the southern half of Canada.

Equisetum laevigatum is a species of horsetail in the family Equisetaceae. It is known by the common names smooth horsetail and smooth scouring rush. This plant is native to much of North America except for northern Canada and southern Mexico. It is usually found in moist areas in sandy and gravelly substrates. It may be annual or perennial. It grows narrow green stems sometimes reaching heights exceeding 1.5 meters. The leaves at the nodes are small, scale-like brownish sheaths and there are occasionally small, spindly branches. The stems are topped with rounded cone-shaped sporangia.