About 15 species; see text
Richardia (Mexican-clover) is a small genus of about 15 species of flowering plants in the family Rubiaceae, native to tropical to warm temperate regions of the Americas, with one species also native to Fiji in the Pacific Ocean. They are mostly annual plants, a few species being herbaceous perennial plants.
Richardia brasiliensis. Guyana and Brazil south to northern Argentina.
Richardia grandiflora. Brazil.
Richardia scabra. Southeastern United States south to Peru.
Richardia tricocco. Southern Louisiana and Texas south to central Mexico.
Richardia Kunth non L. is a synonym of the genus Zantedeschia in the family Araceae.
Germplasm Resources Information Network: Richardia