Perennial; stems 1.5-6 dm, smooth, or hairy at and below the nodes; lvs in 4's, lanceolate or lance-ovate, 3-6 cm, 3-4 times as long as wide, acute or acuminate, 3- nerved, hairy on the veins and margins; infls 1-4 from each of the upper 1-3 nodes, divaricately branched; cor purple; fr smooth or granular, 3-4 mm; often only one carpel fully developed, the other maturing into a small elaiosome. Dry woods in the mts.; Pa. to Va. and Ky., s. to Ga. and Ala. June, July. Hairy-stemmed plants have been called var. hispidum Small, in contrast to the smooth-stemmed var. latifolium.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.