Silphium laciniatum

Plants scapiform, (40-)100-300 cm; taprooted. Stems terete, hirsute, hispid, or scabrous. Leaves: basal persistent, petiolate or sessile; cauline petiolate or sessile; blades lanceolate, linear, ovate, or rhombic, 4-60 × 1-30 cm, usually (proximal) 1-2-pinnately lobed, bases attenuate to truncate, ultimate margins unevenly toothed or entire, apices acute, faces hirsute, hispid, or scabrous. Phyllaries 25-45 in 2-3 series, outer reflexed or appressed, apices acuminate to caudate, abaxial faces hispid to scabrous, ± stipitate-glandular. Ray florets 27-38; corollas yellow. Disc florets 100-275; corollas yellow. Cypselae 10-18 × 6-12 mm; pappi 1-3 mm. 2n = 14. Flowering summer-early fall. Prairies, open, disturbed sites; 50-600 m; Ont.; Ala., Ark., Ill., Ind., Iowa, Kans., Ky., La., Mich., Minn., Miss., Mo., Nebr., N.Mex., N.Y., Ohio, Okla., Pa., S.Dak., Tenn., Tex., Wis.

Coarse, taprooted, rough-hairy, 1-3 m; lvs alternate, deeply pinnatifid or bipinnatifid, the lower very large, to 5 dm, progressively reduced upwards, the uppermost entire and well under 1 dm; heads in a narrow, sometimes racemiform infl, large, the disk 2-3 cm wide; invol 2-4 cm, exceeding the disk, its bracts ovate, acuminate, squarrose, not much imbricate; rays (13-)17-25(-34), 2-5 cm; 2n=14. Prairies; O. to Minn. and S.D., s. to Ala. and Tex.; locally intr. e. along railroads to N.Y. July-Sept. The basal lvs tend to align themselves in a north-south direction.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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