This cosmopolitan weed from Europe is mostly octoploid (2n = 144 but varies from 122 to 152); it is often combined as a subspecies with C. fontanum Baumg. (sensu stricto), which occurs only in cooler regions of Europe. C. vulgatum L. is an ambiguous name proposed for rejection (FNA 5). Altough vulgare is often described as a mat-forming perennial, that character is not obvious in most colls., and biennial or annual behavior may also occur. The species can usually be distinguished from glomeratum (Cr, FNA 5) by its larger larger petals and sepals (ca. 5-7 mm versus ca. 3-5 mm), sepals that lack long distal hairs, inflorescences largely eglandular (versus glandular), with longer pedicels when completely mature (up to 5-12 mm versus 1-5 mm), and larger capsules (mostly 8-10 x 2-3 mm versus 6-8 x 1.5-2 mm), Distinction from the clearly perennial arvense-velutinum complex can be difficult, but F offered the following distinguishing characters for vulgare (as "vulgatum"): basal leafy branches or offshoots herbaceous (versus dry and marcescant), with few or no axillary tufts (versus bearing conspicuous axillary fascicles or leafy tufts), their leaves hirsute and oblong (versus mostly linear to oblong, not hirsute); petals about equalling or slightly exceeding sepals (versus 2-3x sepals), narrow and cleft to middle (versus with broad lobes spreadsing dring anthesis), the claw [constriicted base] ciliate (versus glabrous).