This cosmopolitan annual weed is a highly variable tetraploid (2n = 72), and most colls. need rechecking for other species: especially semidecandrum, brachypetalum or pumilum, but also vulgare (see notes under that name). Both glomeratum and vulgare became common during early settlement (Short 1928-29), especially in overgrazed bluegrass pastures (Gm). C. viscosum L. is an ambiguous name proposed for rejection (FNA 5).