This annual is widespread in central states, with disjunctions or extensions to east, west and south. In Ky. it is most common along drying muddy shores of old sloughs and ponds on broader river bottoms. Colls. from CALD (R. Athey; check EKY), CAMP (KNK) and elsewhere have been named forma depauperatus (Engelm.) Fern. (in Lophotocarpus). However, such plants are often mixed with typical plants and do not appear worth distinguishing (see also B). Compared to congeners in Ky., calycina is annual (versus perennial), and it often has relatively broad leaves with relatively narrow sinus at base and relatively thick inflated petioles. But more research is needed to distinguish species from leaves alone.