Ranunculus platensis Sprengel, an immigrant weedy annual species from South America, was collected first within the United States in Terrebonne Parish, Louisiana, in 1917. Since then, it has spread to six states (Alabama, Florida, Georgia, Mississippi, North Carolina, and Texas) and at least 39 counties and parishes. Based on its biology, the species may be expected to spread generally within the southeastern United States during the next half century.