Stem erect, 4-8 dm, bearded at the nodes and usually sparsely spreading- bristly on the angles; lvs subsessile, narrowly oblong, 3-7 cm, acute or acuminate, sharply serrate, usually acute at base, glabrous; bracts ovate or lance-ovate, denticulate and sparsely ciliate; cal-tube 3-4 mm, glabrous or commonly sparsely villous, the lobes glabrous, deltoid, 2.3-3.4 mm, more than half as wide. Moist soil; Pa. to Io., s. to Ga. and Mo. July-Sept. (S. hyssopifolia var. ambigua; S. ambigua (A. Gray) Britton, not Sm.; S. grayana)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.