Erect, sparsely hirsute, taprooted annual 3-8 dm; lvs ovate or deltoid-ovate, 4-10 cm, scabrellate, decurrent on the long petiole; spikes secund, mostly solitary at the end of the branches, eventually 8-15 cm; cor blue, 3-4 mm wide; fr 2.5-4 mm, divergently 2-lobed to about the middle, each lobe composed of 2 united (but separable) nutlets, each nutlet sharply ridged longitudinally on the back, tapering to the summit, with an abaxial fertile chamber and a swollen, adaxial empty one. A pantropical weed, supposed to be native to Brazil, extending n. to Va., s. Ind., and Mo., and rarely farther as a waif. May-Oct. (Tiaridium i.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.