Introduced annual forb to 1m tall, the base of the stem and the roots red. Bracts below the flowers with spiny tips. Leaves alternating up the stems, 4-7cm long, hairy, with pointed tips. Flowers small (less than 3mm across), greenish, in short cylindrical groups at the bases of the upper leaves and forming dense bristly panicles at the tops of the stems.
Description and photo in G.M. Cunningham, WE Mulham, PL Milthorpe and J H Leigh (1981 and later printings) Plants of Western New South Wales page 284
PlantNET description with line drawing: http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Amaranthus~retroflexus