Easily distinguished from the other Sunflowers by its narrow, linear leaves and yellow heads with purplish disks. Perennial by slender root-stocks; stem rough, 2 to 7 feet high; slender and branched above, usually somewhat hairy below. Leaves firm and tough, slightly rough, linear, entire and sessile, 2 to 7 inches long, one-sixth to one-third of an inch wide, the margins becoming revolute with age or in drying. Lower leaves opposite, the upper ones alternate. Heads with twelve to twenty yellow ray flowers and a purplish disk, the entire head 2 to 3 inches broad. Bracts of the involucres linear-lanceolate and pubescent, their tips scarcely spreading. Chaff of the receptacle entire or three-toothed. Pappus usually two short awns.
Memoir 15 N. Y. State Museum
A. Narrow-Leaved Or Swamp Sunflower - Helianthus augustifolius