Nuttall, J. Acad. Nat. Sci. Philadelphia. 7: 32. 1834.
(A. Gray) Kuntze;
(A. Nelson) Lunell;
(M. Martens) Lunell;
(A. Gray) Lunell;
; S. glaberrima
(A. Gray) Lunell;
(E. S. Steele) E. J. Palmer & Steyermark;
; S. hapemaniana
(M. Martens) Rosendahl & Cronquist;
(Wooton & Standley) C. E. S. Taylor & R. J. Taylor
(A. Gray) Cronquist
; S. moritura
E. S. Steele;
Wooton & Standley;
(10—)30—80 cm; rhizomes short to long.
1—50+, erect, glabrous or sometimes sparsely strigose in arrays; fascicles of small lateral branch leaves often present in axils.
proximal cauline tapering to long, winged petioles, blades oblanceolate to linear-oblanceolate, 50—100(—200) (including petiole) × (5—)10—20(—30) mm, margins entire to serrulate, usually 3-nerved (2 larger lateral nerves), apices acute, mucronate to acuminate and somewhat spinulose, glabrous; mid to distal cauline sessile, blades lanceolate to linear, 40—60 × (2—)4—14 mm, rapidly reduced distally, margins entire, ciliate, faces glabrous.
10—210 in paniculiform arrays, broadly secund-pyramidal or more rhombic to transversely rhombic, (1.5—)3—12(—20) × (1.5—)3—12 cm; branches glabrous with secund heads spreading and arching, sometimes ascending with non-secund heads.
1.4—5 mm, glabrous or sparsely strigose; bracteoles 0—3+ , linear to lanceolate.
narrowly to broadly campanulate, 2.5—4.5 mm.
in 3—4 series, strongly unequal, margins ciliate-fimbriate, especially apically; outer ovate to lanceolate, acute to rounded, inner linear-ovate to oblong or linear-lanceolate, obtuse to rounded.
5—14; laminae 1.5—2(—4) × 0.2—0.5(—0.75) mm.
(6—)8—20; corollas (2—)3—4 mm, lobes 0.4—1 mm.
(obconic) 1—2 mm, glabrous or sparsely strigose;
= 18, 36.
Flowering (Jul—)Aug—Oct. Open sandy and rocky soils, clay soils, prairies, grasslands, pastures, open conifers forests in foothills and proximal elevations of mountains, sandstone ledges, limestone glades, disturbed soils, roadsides; 200—2200+ m; Alta., B.C., Man., Ont., Sask.; Ariz., Ark., Colo., Idaho, Ill., Ind., Kans., Ky., Mich., Minn., Mo., Mont., Nebr., Nev., N.Mex., N.Dak., Okla., Oreg., S.Dak., Tenn., Tex., Utah, Wash., Wyo.; Mexico (Coahuila).
was often introduced along railroad lines farther east. It is a highly variable species. In the east, it can be similar to
and is not always easily distinguished where ranges overlap. In the west, it can similar to smaller plants of
. It is distinguished from the related species by its usually 3-nerved proximal leaves and the usually thin, elongate rhizomes. Across the prairies the species is known to be diploid only (2
= 18). In the Rocky Mountains, tetraploids (2
= 36) are common, the diploids infrequent.
A number of varieties have been described. Shorter, often larger-headed plants (tetraploids when known) from the Rocky Mountains have been treated as var.
). Taller, more leafy-stemmed plants, mostly from the eastern half of the range, but occasionally west to Washington, have been treated as var.
. Plants from Arizona, Colorado, and New Mexico with long, linear leaves have been treated as var.
. Larger-headed plants with narrow bracts from prairies west of the Cascades in Oregon and Washington have been treated as var.
. A. Cronquist (1994) opted not to recognize varieties, noting that all appeared to grade continuously into each other. A detailed study of the species is needed.