In very sandy soil in woodland in the southwestern part of Posey County. I have specimens from three woods of this area. [A variation with linear to linear-oblong leaflets has been called forma angustifolia.] My only specimen is from very sandy soil (Princeton Fine Sand) on a wooded ridge about 2 miles north of Decker, Knox County. The northeastern limit of the range of several species of the southwest occurs on this ridge. The distribution of this form is not well known
Stems erect, simple or virgately branched above, to 1(-1.5) m, softly spreading-hairy; lvs spreading, short-petioled; lfls ovate-oblong to elliptic or obovate, spreading-hairy beneath, ascending-hairy above, those of the main stem 1.5-3.5 cm; apetalous fls numerous in sessile axillary clusters; petaliferous fls purple, 6-8 mm, in dense racemes in the upper axils, on peduncles shorter than the subtending lvs; cal-lobes 1.7-3.5 mm, the 2 uppermost connate less than half their length; fr densely villous; 2n=20. Dry upland woods and barrens; Mass. to n. Fla., w. to Tex., and n. inland to s. Ind., Mo., and Kans. Aug., Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.