Plants (60-)100-120(-240) cm. Leaves: basal and proximal cauline 20-30(-40) cm, proximal cauline blades hastate to deltate or lanceolate. Involucres campanulate to obconic, 11-14 mm. Phyllaries (10-)12-14(-17). Florets 18-55; corollas ochroleucous or white (rarely pinkish), 8-9(-10.5) mm; anthers 2-2.5 mm. Cypselae pale green to light brown, 5-7(-9) mm; pappi 6-7 mm. 2n = 40. Flowering late summer-fall. Rich woods, shaded, wet areas bordering streams; 10-300+ m; Conn., Ill., Ind., Iowa, Ky., Md., Mass., Minn., Mo., N.J., N.Y., N.C., Ohio, Pa., R.I., Tenn., Va., W.Va., Wis. Hasteola suaveolens is now less common or absent in the northeastern part of its historic range.
From Flora of Indiana (1940) by Charles C. Deam
Local near the dunes about Lake Michigan, and then very local until the southern part of the state is reached, where it is very local to infrequent. In addition to my records it has been reported from Hamilton, Lake, La Porte, and Tippecanoe Counties. It is always found in moist or wet grounds, usually near a stream, and it spreads rapidly by underground stems. I planted this and the next two species in alluvial soil in bottomland, and the other two lived only a few years, while Cacalia suaveolens has spread about a foot each year through an adjacent bluegrass sod.
Perennial 1-2.5 m with long, fleshy-fibrous roots, glabrous or nearly so; stem striate or grooved, simple to the infl, leafy; middle and lower lvs triangular-hastate, 5-20 cm, nearly or quite as wide, sharply toothed, conspicuously petioled; upper lvs progressively less hastate and with shorter, more winged petioles; heads in a flat-topped infl, commonly 20-40-fld, the disk 7-11 mm wide; invol 1 cm, its principal bracts 10-15, commonly with some reduced but conspicuous, loose, subulate outer ones; receptacle flat, deeply pitted; 2n=40. Riverbanks and moist low ground; R.I. and Conn., w. to se. Minn., s. to Md., Ky., Tenn., Ill., and in the mts. to Ga. July-Oct. (Synosma s.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.