This variable perennial (from a small rounded corm) has a somewhat fragmented southeastern range from N.Car. and Ga. to Mo. and Tex. (W). There are no clear differences in habitat from the other species of Ptliimnium, but it is generally less common and more concentrated in more natural wetlands. It usuallty flowers and fruits later (Jul-Oct versus Apr-Aug). It is potentially the tallest species, up to 1.5 m (about double the others); mid-stem leaves have 8-16 nodes (versus 2-10), and more crowded verticillate leaf segments (usually 3-6 versus 1-3 per node). It also tends fo have longer styles (1.5-3 mm versus 0.2-1.5 mm), and larger fruits (2.2-4 mm versus 1-4.2 mm); 2n = 22 or 32 (versus 14 or 28).