Plants 100-300 cm (rhizomatous). Stems smooth to weakly striate (glaucous). Basal leaves: blades usually ovate or ovate-cordate, to 21 cm (bases truncate or subcordate), margins shallowly lobed or dentate (sinuses smooth). Cauline leaves: (abaxial faces pale green, glaucous) proximal petiolate, ± deltate, margins coarsely dentate; distal petiolate or sessile, smaller. Involucres (7.5-)8-10(-10.5) mm. Phyllaries (pale green) oblong, midveins not winged (tips obtuse to acute, sparsely papillate). Corollas white, usually with green, sometimes purple, 8-9.5(-13) mm. Cypselae fusiform or ellipsoid, 4-5 mm (brown or purplish, 8-10-ribbed); pappi 5-6(-7) mm (readily falling). 2n = 50, 52, 56.
Much like no. 2 [Cacalia muehlenbergii (Sch. Bip.) Fernald], and hybridizing with it; stem glaucous, terete or slightly striate; lvs pale and glaucous beneath, averaging smaller, proportionately longer, and more pointed (the lower triangular-ovate), with fewer and larger teeth, or merely shallowly lobed, the sinuses smooth; 2n=50-56. Woods and moist or rather dry open places; N.J. and Pa. to s. Minn., s. to Ga., w. Fla., and Okla. (Mesadenia a.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.