Eudicots (unranked): Core eudicots Order: Caryophyllales Family: Amaranthaceae Subfamily: Amaranthoideae Genus: Amaranthus L. Species See text. Amaranthus , collectively known as amaranth , is a cosmopolitan genus of annual or short-lived perennial plants . Catkin -like cymes of densely packed flowers are borne in summer or autumn. [ 1 ] Approximately