Plants 50–100(–200) cm. Leaves: basal blades ± elliptic, mostly 15–40 cm × 100–200+ mm (bases decurrent onto strongly ribbed petioles, margins callose-denticulate, otherwise entire, abaxial faces velvety-woolly, adaxial thinly hairy); cauline blades ovate or elliptic to lanceolate, 10–30 cm × 45–120 mm, bases cordate, clasping, margins serrate. Involucres (20–)30–40 mm diam. Outer phyllaries ovate, oblong, or ± deltate to lanceolate, 12–20(–25+) × 6–8(–20+) mm (abaxially velvety-hairy); inner phyllaries progressively narrower, less hairy, more scarious. Ray florets (15–)50–100+; corolla laminae (10–)20–30+ mm. Disc corollas 9–11 mm. Cypselae 3–4 mm, glabrous; pappi of (40–)50–60 basally connate, barbellate bristles or setiform scales 6–10 mm. 2n = 20.

Flowering mid–late summer. Roadsides, waste places, streamsides; 0–300(–600+) m; introduced; B.C., Man., N.B., N.S., Ont., P.E.I., Que.; Calif., Conn., Del., Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Mo., N.H., N.J., N.Y., N.C., Ohio, Oreg., Pa., R.I., Tenn., Utah, Vt., Va., Wash., Wis.; Europe; introduced, Asia and beyond.

Inula helenium is widespread in the Old World.