Annual grass to 1m tall. Leaves with a hairless sheath at the base. Leaves 9-40cm long, 4-14mm wide, flat, hairless. Ligule absent. Spikelets 4-6mm long. Seeds with 0 bristles. Mature seed groups spreading. Endangered SA.
PlantNET description with line drawings: http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Echinochloa~lacunaria
ausgrass2 description with photo: http://ausgrass2.myspecies.info/content/echinochloa-lacunaria