In the genus Nymphoides (floating-heart), at least six native and naturalized species are known to occur in the USA. Among the native species is Nymphoides humboldtiana, a species recently confirmed to reach its northern range limit in southern Texas. Plants similar in appearance to N. humboldtiana have been reported from Florida, where both white- and yellow-petaled variants have been identified as Nymphoides indica, a paleotropical species. We examined specimens using molecular (DNA) and morphological data to ascertain correct species identifications for the Florida plants. Sequence data from nuclear internal transcribed spacer and plastid trnK/matK regions indicated that Florida plants are not conspecific with N. humboldtiana, and that the white and yellow floral color variants attributed to N. indica actually represent separate species. We identified the white-petaled plants as N. indica, a likely escapee from the water garden trade in which the species is commonly grown. The yellow-petaled plants were identified by molecular data as Nymphoides grayana, and their identification was confirmed subsequently by morphological data. Nymphoides grayana is native to the Caribbean but was unknown previously in the USA. Because of the proximity of native N. grayana populations and the absence of this species in the water garden trade, we conclude that the Florida specimens arrived via a natural range expansion.