Taprooted annual 2-7 dm, branched when well developed; stem swollen at the nodes, hispid-setose (notably on the angles) with long, spreading or slightly reflexed hairs, and often also with shorter but still prominent, gland-tipped hairs, especially just beneath the upper nodes; lvs petiolate, with rhombic-elliptic to ±ovate, coarsely blunt-serrate, basally rounded or cuneate, ±strigose or hirsute blade 3-10 נ1-5 cm; verticils dense, generally several, the lower often remote; cal ca 1 cm at anthesis, somewhat larger in fr, the erect spinescent lobes about equaling the tube, elongating to 5-10 mm; cor white or pink or variegated, commonly with 2 yellow or white spots; 2n=32. Native of Eurasia, intr. and often appearing as a native in our range, especially northward. June-Sept. Var. tetrahit has the cor mostly 15-23 mm, the middle lobe of the lower lip nearly square, not emarginate. Var. bifida (Boenn.) Lej. & Courtois has smaller fls, seldom over 15 mm, the central lobe of the lower lip emarginate or cleft. (G. bifida)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.