Perennials, 30-100 cm. Stems usually 1, usually branched distally, strongly winged, glabrous or sparsely hairy proximally, sparsely to moderately hairy distally. Leaves glabrous or sparsely to moderately hairy; basal blades oblanceolate to obovate or spatulate, entire or serrate; proximal and mid blades oblanceolate to lanceolate, entire or toothed; distal blades lanceolate to lance-linear, entire. Heads (1-)5-50(-80+) per plant, in paniculiform arrays. Peduncles 3-10 cm, sparsely to moderately hairy. Involucres globoid to usually ovoid, 8-17 × 9-17 mm. Phyllaries (connate proximally) moderately to densely hairy. Ray florets usually 8-13, neuter, sometimes 0; corollas yellow to reddish brown to red to purple, 10-20 × 5-10 mm. Disc florets 250-500(-700+); corollas yellow proximally and purple distally or purple throughout, 2.3-3.7 mm, lobes 4(-5). Cypselae 1-1.2 mm, moderately hairy; pappi of 5-6 entire, aristate scales 0.6-1(-1.7) mm. 2n = 28. Flowering (Apr-)May-Jul(-Oct). Ditches, fields, washes, along streams; 10-900 m; N.S., Ont., Que.; Ala., Ark., Fla., Ga., Ill., Ind., Ky., La., Md., Mass., Mich., Miss., Mo., N.J., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Va., W.Va., Wis. It has been suggested that Helenium flexuosum may be of hybrid origin from H. campestre (perennial, 2n = 28) and some member of Helenium sect. Tetrodus (H. F. L. Rock 1957). The only member of sect. Tetrodus that has a chromosome number of 2n = 28 is H. linifolium, an annual from southern Texas.
From Flora of Indiana (1940) by Charles C. Deam
Apparently restricted to the southern part of the state, although Peattie cites specimens found in Lake County near Miller. It is a weed and is likely to appear almost anywhere. Most of my specimens were found in moist, hard, white clay soil in pastures, where it often covered acres. It seems to prefer a slightly acid soil. I have a specimen collected in Posey County in 1878 by Schneck which, to my knowledge, is the oldest record of it in the state. It is reputed to be very poisonous to stock. I add the following note which I made August 19, 1933: "Today I traveled over U. S. Road 50 through Lawrence, Martin, and Knox Counties, and I found this species to be a common weed in the western part of Lawrence County, in Martin County, and in the eastern part of Knox County. I noted it in many fields where it formed almost complete stands over 3-5 acres. I saw hogs and cattle in some of the fields but apparently they did not eat it."
Fibrous-rooted perennial 2-10 dm, ±puberulent or villous- puberulent at least on the stem, the lower part of the stem generally spreading-villous; lvs decurrent but smaller, fewer, and more erect than in no. 1 [Helenium autumnale L.], entire or subentire, the lowermost ones oblanceolate, commonly deciduous, the others oblong or lanceolate to lance-linear, sessile, generally not much reduced upwards, 3-12 נ0.5-2 cm; heads in well developed plants numerous in an open, corymbiform, leafy-bracteate infl, the disk subglobose or ovoid-globose, 6-15 mm wide, red-brown or purplish; rays ca 8 to ca 13, neutral, sometimes purplish at base, (0.5-)1-2 cm (rarely wanting); disk-fls predominantly 4-merous; pappus- scales 5(-8), ovate or lanceolate, shortly awn-tipped, ca (0.5-)1 mm overall; 2n=28. Moist ground and waste places; Mass. and N.H. to Fla., w. to Wis., Ill., Mo. and Tex., apparently only intr. northward. June-Oct. (H. nudiflorum; H. polyphyllum)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.