Perennials, 100-200 cm (rhizomatous). Stems erect, glabrous or glabrate. Leaves cauline; mostly opposite, sometimes alternate (distal); petioles 1-3 cm; blades (light to dark green, 3-nerved distal to bases) lanceolate to lance-ovate or ovate, 7-18 × 2-10 cm, bases subcordate to ± cuneate, margins entire to ± serrate, abaxial faces glabrous or tomentulose, usually densely gland-dotted. Heads 3-15. Peduncles 1-9 cm. Involucres cylindric to hemispheric, 8-20 mm diam. Phyllaries 18-25 (erect, loose, or squarrose), lanceolate, 5.5-10 × 1.5-3 mm (equaling or slightly surpassing discs), (margins usually ciliate) apices acute to acuminate, abaxial faces glabrous or hispidulous, usually not gland-dotted. Paleae 5.3-6.5 mm, 3-toothed. Ray florets 10-20; laminae ca. 12-20(-30) mm. Disc florets 35+; corollas 5.5-6.5 mm, lobes yellow; anthers dark, appendages dark or reddish brown. Cypselae 4-5.5 mm, glabrate; Pappus of 2 aristate scales (1-)2-2.5 mm. 2n = 68, 102. Flowering late summer-fall. Woods , roadsides, prairies; 0-1500 m; Ont., Que.; Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Vt., Va., W.Va., Wis. Helianthus strumosus is variable, particularly for leaf shape and indument; sufficient study has not been undertaken to evaluate whether regional forms deserve taxonomic recognition. Hybridization with other polyploids, including H. decapetalus, H. hirsutus, and H. tuberosus, further complicates the situation. It differs from H. tuberosus in having glabrous (or glabrate) stems and in lacking tubers.

Rhizomatous perennial; stems 1-2 m, glabrous below the infl or with a few long hairs, often glaucous; lvs opposite or the uppermost alternate, relatively thick and firm, scabrous-hispid above, green and moderately short-hairy to more often glaucous and subglabrous beneath, mostly broadly lanceolate to ovate and 8-20 נ2.5-10 cm (sometimes narrower), long-acuminate, shallowly toothed or subentire, commonly decurrent onto the 0.5-3 cm petiole; disk yellow, 1.2-2.5 cm wide; invol bracts subequal, lanceolate, somewhat loose, especially the long-acuminate tips, which commonly equal or slightly surpass the disk; rays 8-15, 1.5-4 cm; 2n=68, 102. Woods and open places; Me. to Fla., w. to Minn., e. Kans., and e. Tex. July-Sept.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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