Perennials, 50-150+ cm (with crown buds, rhizomes absent or poorly developed). Stems erect, usually ± hairy. Leaves mostly cauline; opposite or alternate; sessile or subsessile; blades (3-nerved near bases) narrowly lanceolate to linear, 8-15 × 0.15-0.5(-1) cm, bases cuneate , margins entire (revolute, abaxial face sometimes obscured by rolled margins), abaxial faces strigose to hispid or hirsute, sometimes (adaxial not) gland-dotted. Heads 3-16. Peduncles 5-15 cm. Involucres shallowly hemispheric, 10-20 mm diam. Phyllaries 25-32 (loose), lanceolate, 4-9 × 1-2 mm, apices acute to slightly acuminate, abaxial faces usually scabrous, rarely glabrous, usually gland-dotted. Paleae (oblanceolate) 5.5-6.5 mm, entire or ± 3-toothed (apices purplish, mucronate, gland-dotted). Ray florets 10-20; laminae 10-20 mm (abaxial faces gland-dotted). Disc florets 75+; corollas 4-4.5 mm, lobes yellow; anthers dark brown or black, appendages dark (style branches usually yellow). Cypselae 2-3 mm, glabrate; pappi of 2 aristate scales 1.5-2.1 mm. 2n = 34. Flowering late summer-fall. Open to shaded, usually moist places; 10-700 m; Ala., Ark., Fla., Ga., Ind., Iowa, Ky., La., Md., Miss., Mo., N.J., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Va., W.Va. The distal parts of Helianthus angustifolius are identical in appearance to those of H. simulans; plants of the latter are taller (200+ cm) and more robust. The leaves are not only narrower in H. angustifolius but also tend to be more strongly revolute (abaxial faces sometimes scarcely visible).
From Flora of Indiana (1940) by Charles C. Deam
In 1931 in Pike County I found this species rather common over an area of about three acres in a large creek-bottom pasture field. I noted that the cattle did not eat it. I found it also in a low pasture field in Jefferson County. Doubtless it has been introduced although the field in Pike County is far removed from a railroad and it is the second field back from a little used road. No doubt it came in through grass seed. I introduced it in our garden which has neutral soil. It gradually died out in four years. Doubtless it requires a slightly acid soil, the kind in which I found it.
Fibrous-rooted perennial with crown-buds, nearly or quite without rhizomes; stem solitary, 0.5-1.5(-2) m, ±hairy, especially below; lvs numerous, sessile or nearly so, commonly alternate except near the base, linear or nearly so and revolute-margined, mostly 5-15(-20) cm נ2-10(-15) mm and 10-30 times as long as wide, dark green and scabrous above, pale beneath with fine, loose, sometimes deciduous hairs, and often also atomiferous-glandular; petiolate basal lvs with broader blade sometimes present; disk red-purple (yellow), (1-)1.5-2 cm wide; invol bracts narrow, at least the inner with loose, narrow tip seldom surpassing the disk; rays (8-)10-15(-21), 1.5-3 cm; 2n=34. Swamps and moist places; L.I. to Fla. and Tex., chiefly near the coast in our range, but inland to s. O., s. Ind., and s. Mo. Aug.-Oct.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.