This is a variable widespread species, extending from eastern U.S.A. to South America. But in most of its northern range only var. nictitans has generally been recognized by recent authors (e.g. Y, W). Included here is var. leiocarpa Fern., which was reportedly collected in BELL (B). It differs from fasciculata as follows (Isely 1990, W): corolla 0.8-1.0 cm in diameter (versus 2.5-3.5 cm), the larger petals 4-8 mm long (versus 15-20 mm); functional stamens 5-8 (versus 10); pedicels, including the two bracteoles, 1.5-4 mm long from leaf stem (versus 10-15 mm). legumes mostly 2-4 cm long (versus 3-5.5 cm).