5. Arnoglossum ovatum (Walter) H. Robinson, Phytologia. 28: 294. 1974.
Cacalia ovata Walter, Fl. Carol., 196. 1788; Arnoglossum ovatum var. lanceolatum (Nuttall) D. B. Ward; C. elliottii (R. M. Harper) Shinners; C. lanceolata Nuttall; C. lanceolata var. elliottii (R. M. Harper) Kral & R. K. Godfrey; Conophora ovata (Walter) Nieuwland; Mesadenia angustifolia Rydberg; M. dentata Rafinesque; M. elliottii R. M. Harper; M. lanceolata (Nuttall) Rafinesque; M. lanceolata var. virescens R. M. Harper; M. maxima R. M. Harper; M. ovata (Walter) Rafinesque; Senecio boscianus Schultz-Bipontinus; S. walteri Schultz-Bipontinus
Plants 50–300 cm (weakly rhizomatous). Stems round. Basal leaves: blades ovate to narrowly lanceolate or lance-linear, to 30+ cm, margins usually entire. Cauline leaves: proximal petiolate, ovate to narrowly lanceolate or lance-linear, margins usually entire; distal sessile, smaller. Involucres 8–10 mm. Phyllaries (± purple-tinged) lance-ovate, midveins not winged (tips acute to acuminate, papillate). Corollas usually white or greenish, rarely purplish, 8–9(–10) mm. Cypselae fusiform or clavate, 4–5 mm (dark brown, 7–8-ribbed); pappi (5–)6–7.5 mm. 2n = 50, 52, 56.
Flowering (May–)Aug–Oct(–Dec). Wet, sandy woods, lowlands, savannas, roadsides; 0–300 m; Ala., Fla., Ga., La., Miss., N.C., S.C., Tex.
Arnoglossum ovatum is the most variable species in the genus (as implied by synonymy). Extreme forms (very narrow-leaved, e.g., Cacalia lanceolata form, and broadly ovate-leaved forms) look very distinctive; intergradations occur. Differences could be because of dysploid chromosome races, variances in habitat, or some unknown factors.