Cacalia diversifolia Torrey & A. Gray, Fl. N. Amer. 2: 435. 1843; Conophora diversifolia (Torrey & A. Gray) Nieuwland; Mesadenia difformis Small; M. diversifolia (Torrey & A. Gray) Greene; Senecio floridanus Schultz-Bipontinus

Plants 100–200(–300) cm. Stems proximally ribbed (and purplish), distally angular (and greenish). Basal leaves: (petioles with brownish hairs) blades ovate to cordate-ovate, to 10 cm (bases truncate), margins denticulate. Cauline leaves: proximal petiolate, deltate-hastate, margins dentate (faces glabrous); distal petiolate or sessile, smaller (faces finely puberulent). Involucres (7.5–)9–11 mm. Phyllaries lance-ovate, midvein wings uniform or highest at apices. Corollas white or purplish, 8.5–9.5(–10.5) mm. Cypselae fusiform, 3 mm; pappi (6–)7–8 mm. 2n = 50.

Flowering mid May–early Jul (Aug–Sep, peninsular Florida). Wet or mucky soils, along streams, swamps, woodlands; of conservation concern; 0–100 m; Ala., Fla., Ga.

Arnoglossum diversifolium grows primarily in the Florida panhandle and adjacent Alabama and Georgia, and in Putnam and Levy counties, Florida.