Aster sagittifolius Willd.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Plants with a branched caudex or short rhizome; stems 4-12 dm, ± glabrous below the infl, or the upper part occasionally villous-puberulent in lines; lvs rather thick, shallowly toothed, glabrous or scabrous above, glabrous or ± villous-hirsute with flattened hairs beneath, the lowest ones ovate or more often lance-ovate, acuminate, cordate, 6-15 × 2-6 cm, long-petiolate, those above progressively less cordate or merely abruptly narrowed to the shorter, often broadly winged petiole, or the upper tapering and sessile; infl paniculiform, elongate, with ± strongly ascending, narrowly bracteate branches, the heads often very numerous, on narrowly bracteate peduncles rarely over 1 cm and usually under 5 mm, thus appearing crowded; invol 4-6 mm, its imbricate bracts glabrous except for the sometimes ciliolate margins, very slender and long-pointed, with elongate, narrow green tip, often minutely purple-tipped under a lens; rays 8-20, usually pale blue or lilac, sometimes white, 4-8 mm; achenes glabrous; 2n=16, ?18, ?36, 48. Streambanks, woods, and less often in open places, often in more mesic habitats than no. 32 [Aster drummondii Lindl.], with which it hybridizes extensively; sw. Vt. to Minn., s. to Ga., w. Fla., Miss., and Mo. (A. hirtellus; A. urophyllus) My interpretation of the name A. sagittifolius is based on examination of the type material at Berlin.