Annual or biennial, dioecious herb, 20-60 cm tall, erect, light green, glabrous. Leaves ovate to triangular-hastate, entire or dentate, lower long-petiolate, usually entire, Staminate flowers in interrupted spiciform panicles, with 4 (-5) perianth segments and stamens; pistillate flowers in dense axillary sessile clusters, each separated and falling so in fruit; bracteoles in fruit orbicular-obovate, usually broader than long, free, with (f. spinosa) or without (f. glabra) divergent spines at the apex.