Erect annual, mostly up to 90(–150) cm, similar in habit to A. spinosus and with similar leaf-size and shape, but often less coarse. Paired axillary spines absent. Lower flower clusters axillary, female, 4–10 mm in diam.; upper clusters leafless, forming simple or (the terminal at least) branched spikes 3–15(–25) cm long and 6–8(–10) cm wide, the spikes male for up to c. the apical 1 cm. Tepals of female flowers (4–)5, 1.5–2.75 mm, oblong or spathulate-oblong, obtuse or sometimes (especially towards the male flowers) acute, mucronulate, usually with a greenish dorsal vitta above. Stigmas 3. Capsule ovoid-urceolate, c. 1.5–1.75 mm, with a short inflated beak below the style-base, circumscissile, the lid strongly rugulose. Seeds faintly reticulate, lenticular.