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).
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.