Common Spike -rush
Perennial rush to 90cm tall. Leaves reduced to membranous sheaths at the base of the plant. Flower stem cylindrical, usually ribbed, triangular under the spikelet. Spikelet 10-30mm long, 3-7mm wide, straw coloured to brown, with 0 petals, of many florets, a single oval to cylindrical spikelet at the top of the stem. Grows in shallow water.
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 164
PlantNET description with line drawings and photo: http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Eleocharis~acuta