Plants to 10 dm. Stems branching, ribbed. Leaves to 35 cm; petiole 2-10 cm; blade deeply 5-9-lobed; margins irregularly dentate or crenate, rarely laciniate. Inflorescences: peduncle 2-10 cm. Flowers: pedicels 5-35 mm; sepals to 1 cm; petals bright yellow, obovate to oblong, to 2 cm wide; style ca. 1 mm. Capsules linear to narrowly oblong, 2-5 cm, glabrous. Seeds black, reticulate-pitted. Flowering spring-summer. Moist to dry woods, thickets, fields, hedgerows and fences, roadsides, railroads, and waste ground; 0-1000 m; introduced; B.C., N.B., N.S., Ont., P.E.I., Que.; Conn., Del., Ill., Ind., Iowa, Maine, Md., Mass., Mich., Minn., Mo., Mont., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., Utah, Vt., Va., Wash., W.Va., Wis.; Eurasia. The irritating sap of Chelidonium has been used to treat warts. In the vegetative state, this weedy introduction from Eurasia is difficult to distinguish from the native Stylophorum diphyllum .
Branched, 3-8 dm; cauline lvs several, alternate, much like those of Stylophorum diphyllum; sep glabrous; pet 1 cm; fr 3-5 cm; 2n=12. Eurasian sp., well established in moist soil from Que. to Io., s. to Ga. and Mo. Apr.-Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.