This is a widespread weed in warmer regions of the Americas. In Ky. it has been casually confused with subglabrata, but differs in its annual (versus rhizomatous) habit; its more coarsely dentate largest leaves (versus sinuate-dentate); and its smaller fresh flowers (ca. 4-10 x 6-15 mm versus 11-17 x 15-25 mm), which lack purple maculations. Some colls. may be referable to the rather poorly defined, southern or western var. pendula (Rydb.) Waterfall, but this is not confirmed. BA reported the closely related Ozarkian taxon, P. missouriensis Mack. & Bush, but no colls. have been verified.