Erect or occasionally ascending annual, up to 3 m in some cultivated forms but much less in the wild, not infrequently ± reddish-tinted in part or throughout. Stems stout, simple to much-branched, glabrous or increasingly furnished upwards with long multicellular hairs. Petioles up to 15 cm long but scarcely longer than the 3–19(–30) x 1.5–8(–12) cm, broadly lanceolate to rhomboid or ovate blade, obtuse to subacute, glabrous or thinly pilose on the lower surface of the margins and primary venation. Flowers in axillary and terminal “spikes” of cymose clusters which become increasingly congested above, the terminal inflorescence of a single spike or a broad, much-branched panicle up to c. 45 x 25 cm with the terminal spike often somewhat nodding, male and female flowers intermixed. Tepals of female flowers 5, 1.5–3.5 mm, lanceolate-oblong, acute-aristate to blunt and mucronulate. Stigmas (2–)3. Capsule subglobose to ovoid-urceolate, 2–3 mm with a small and smooth to inflated or wrinkled beak, circumscissile. Seeds faintly reticulate, lenticular.