Plants 50-100 cm (weakly rhizomatous). Stems angulate. Basal leaves: blades broadly elliptic, to 17 cm, margins entire or sinuate. Cauline leaves: proximal (and mid) petiolate, elliptic (bases rounded), margins entire or serrulate; distal petiolate or sessile, smaller (narrower). Involucres (9.5-)10-12(-14) mm. Phyllaries (pale green) ovate, midvein wings uniform or highest at apices. Corollas white or greenish, 8-10(-11.5) mm. Cypselae fusiform or clavate, 4-5 mm (dark brown, 12-15-ribbed); pappi (6-)7-8(-9) mm. 2n = 54.
Flowering May (south)-Aug (north). Wet prairies and pastures, usually in boggy areas in north; 0-600 m; Ont.; Ala., Ark., Ill., Ind., Iowa, Kans., Ky., La., Mich., Minn., Miss., Mo., Nebr., Ohio, Okla., S.Dak., Tenn., Tex., Wis.
This is a local species found only in marly springy places. Where it is found, it is usually a common plant. Its absence in the northeastern part of the state is of interest. If it occurs there, it is rare, because I have collected intensively in these counties without finding it.
Stout, glabrous perennial 6-18 dm from a short, tuberous-thickened base and fleshy-fibrous roots; stem striate-angled; lvs thick and firm, entire or nearly so, with several prominent longitudinal nerves converging toward the summit; basal and lowermost cauline lvs conspicuously long-petioled, the blade 6-20 × 2-10 cm, commonly elliptic and tapering to the base, or deltoid-ovate and subtruncate in robust specimens; cauline lvs few, conspicuously reduced upwards, becoming sessile or subsessile; otherwise as in no. 2 [Cacalia muehlenbergii (Sch. Bip.) Fernald]; 2n=54. Wet prairies and marshy or boggy places; O. and s. Ont. to Minn. and e. S.D., s. to Ala. and Tex. June-Aug. (C. tuberosa; Mesadenia t.)
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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