Cyperus erythrorhizos Muhlenberg. Redrooted Flatsedge. Phen: Jul-Dec. Hab: Marshes, ditches, shores, mud flats. Dist: MA west to ND and WA, south to n. FL, LA, TX, AZ, CA, and Mexico (BCN, TAB, TAM).
ID notes: This species is frequently confused with C. odoratus, with which it is often closely associated. The neatly quadrangular spikelets with tiny (≤ 1.5 mm), closely imbricate scales (vs. terete, jointed spikelets with > 2 mm, loosely spaced scales) easily distinguish even depauperate plants of C. erythrorhizos at a glance.
Origin/Endemic status: Native
Syn: = Ar, C, ETx1, F, FNA23, G, GrPl, GW1, Il, K1, K3, K4, Mex, Mi, Mo1, NcTx, NE, NY, Pa, RAB, Tn, Tx, Va, W, WH3, WV; > Cyperus erythrorhizos Muhl. – S; > Cyperus halei Torr. ex Britton – S