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.