This robust pantropical annual is widespread,(and variable) from South America to warmer regions of southeastern states. It usually grows on damp to seasonally dry shores and uplands, often with sandy or gravelly soils. Height is ranges from ca. 5 to 50 cm; 2n = 30. It is known as far north as c. Mo., s. Ill. and s. Ind. (FNA 23, K, Y). The only Ky. record is a coll. from Mantle Rock in LIVI, made by M. Medley (#15533-86 for WKY; now at APSC). There may also be old obscure colls. of C.W. Short (e.g. at Copenhagen) without locality (M).