American burnweed

Annuals, (50–)100–200 cm (glabrous or unevenly coarse-tomentose, sometimes ± succulent). Taproots with tufts of fibrous roots. Stems 1(–2+), erect. Leaves evenly distributed (proximal often withering before flowering); indistinctly petiolate or subsessile; blades ovate-lanceolate to lanceolate, (3–)6–20 × (1–)2–8 cm, margins subentire to serrate or weakly lobed (distal leaves clasping, bractlike). Heads 2–20(–40) in ± corymbiform arrays. Involucres urceolate or obconic, 10–17 mm. Phyllaries usually 21. Receptacles (disclike, conspicuously expanded when fresh) 5–12 mm diam. Cypselae 2.3–3 or 4–5 mm, nerves 10–12 or 16–20, faces puberulent between nerves or glabrous.