This cosmopolitan weed originates from southwestern U.S.A. to South America (Cr; FNA 21). It has been reported from JEFF (K), MCRA (R. Athey catalog), and NELS (Greenwell 1935), but no confirmed colls. have been seen (M). G. parviflora (2n = 16) has often been confused with quadriradiata (2n = 32, 48, 64). Reported diagnostic characters are diverse, and published keys have significant differences (e.g. compare W with FNA 21).