Annual herb 10–75(–200) cm high, erect or procumbent, much branched, the branches opposite and decussate, green or red to pinkish, pilose or more often glabrous. Leaves green or yellowgreen, narrowly elliptic to oblanceolate, 1–7.5 cm long, 0.3–2 cm wide, base narrowed into a pseudopetiole but the very base widening and connate with the opposite leaf, margins serrulate to serrate, 3-veined from base, glabrous or puberulous. Capitula many in congested axillary and terminal cymes or glomerules; individual capitula oblong, heterogamous, some with a single female floret, some with 1 female and 1 bisexual floret, some with 2–4 bisexual florets only; involucre 4–5 mm long; phyllaries few, 2-seriate, 4–5 mm long. Female florets with ray yellow, suborbicular, 0.5–1 mm long, the tube green and ± 1 mm long; disc florets yellow with green base, 2–2.5 mm long, with pilose base. Achenes black, narrowly obovoid, 1.7–2.6 mm long, glabrous; pappus absent. Fig. 149 (page 724).