Tufted annual. Culms ascending to erect, to 60 cm high. Leaves mostly glabrous; blade flat to folded, to 15 cm long and 8 mm wide; sheath keeled; ligule 1–1.5 mm long. Inflorescence a spike or spike-like raceme, sometimes interrupted, 3–8 cm long, the axis flattened and flexuose; involucre (burr) 5–9 mm long, lacking a basal series of bristles, retrorsely barbed apically, spines all flat, the longest to 4 mm long; spines numbering 20–35 in total; body of burr shortly hairy. Spikelets 1–3 per burr, 3.5–5.5 mm long; lower glume 1-nerved, acute, 1–3 mm long; upper glume 5-nerved, acute, 3–5 mm long; lower floret male, its lemma equal to or slightly longer than upper glume, palea subequal to lemma; fertile lemma as long as spikelet, 5-nerved, ovate, acuminate, papery; palea subequal to lemma. Flowers Jan. (1 record)
LoM, MuF. Known in Victoria from a single 1986 collection from Barmah Forest near the Murray River. Possibly more widespread and likely to be mistaken for the very similar C. longispinus. Native to North America; naturalised in all mainland states.
