American feverfew

Parthenium integrifolium L. (Asteraceae) is an erect perennial herb of eastern North American prairies, glades, and open woods, growing 0.4–1.2 m tall from a thick, woody, aromatic taproot. Stems are stout, ridged, and roughly pubescent. Basal leaves are long-petiolate, broadly ovate to lanceolate, 10–25 cm long, with coarsely toothed or crenate margins and rough, sandpapery surfaces; cauline leaves become smaller, sessile, and clasping upward. The inflorescence is a flat-topped corymb of numerous small heads about 5–8 mm wide, each with five short, white, three-lobed ray florets and a center of cream-white disk florets. Achenes are flattened, obovate, and crowned by two small awns. Flowering occurs from late spring through summer. The species is native from New York and Wisconsin south to Georgia and Texas.