Senecio atriplicifolius (Linnaeus) Hooker var. reniformis Hooker, Fl. Bor.-Amer. 1: 332. 1834, based on Cacalia reniformis Muhlenberg ex Willdenow, Sp. Pl. 3: 1735. 1803, not Lamarck 1778; Conophora reniformis (Hooker) Nieuwland; Mesadenia reniformis (Hooker) Rafinesque; S. reniformis (Hooker) MacMillan

Plants 100–300 cm. Stems ridged to angulate (usually glabrous, rarely sparsely puberulent distally, not glaucous). Basal leaves: (petioles to 30 cm) blades (with 3–5 main veins) reniform or ovate-cordate, to 40+ cm, margins lobed or dentate. Cauline leaves: proximal petiolate, blades ovate, margins entire, serrate, or dentate; distal petiolate or sessile, smaller (rarely hairy). Involucres (8–)10–13(–14) mm. Phyllaries pale green, narrowly ovate, midveins not winged (tips obtuse). Corollas white or greenish, 8–9(–10.5) mm. Cypselae fusiform or clavate, 4–5 mm (dark brown or purple, 4–5-ribbed); pappi 6–8 mm. 2n = 50.

Flowering mid May–early Sep. Open woods; 10–500 m; Ala., Ark., Del., Ga., Ill., Ind., Iowa, Ky., Md., Minn., Miss., Mo., N.J., N.C., Ohio, Okla., Pa., Tenn., Va., W.Va., Wis.

Arnoglossum muehlenbergii of H. Robinson, Cacalia muhlenbergii of Fernald, and Mesadenia muhlenbergii of Rydberg were based on Senecio muehlenbergii Schultz-Bipontinus, a superfluous name based on Cacalia reniformis Muhlenberg ex Willdenow.