Much like A. quinquefolia, and not sharply distinct, averaging a little larger, mostly 1.5-3 dm; lfls of the involucre rhombic-ovate to elliptic, usually 3.5-7 cm, the lateral ones coarsely toothed nearly to the rounded base along the outer margin, rarely incised, the central lfl broadest at or below the middle and serrate to below the middle. Rich mt. woods; s. Pa. to Ga. Apr., May. (A. trifolia of auth., misapplied) Perhaps better treated as A. quinquefolia var. lancifolia (Pursh) Fosberg. Very small (merely depauperate?) plants from the southern Appalachians, smaller in all dimensions than A. quinquefolia and A. lancifolia, are rarely observed and have been described as A. minima DC. Their proper status remains to be determined.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.