This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Biennial. Propagates by seeds. Time of bloom: April to August.
Seed-time: June to September.
Range: Maine to Ontario, southward to Virginia. Habitat: Farmyards, roadsides, waste places, borders of woods.
Chelidon means a swallow, and it is said that the swallows come with the first opening flower of this plant and go as the last bloom fades. When bruised, the weed exudes an orange-colored juice with a disagreeable odor, bitter and acrid, once considered a sure cure for warts, corns, pimples, boils, and "tetters" of every kind, even to the painful felon. It still has good standing in the United States Pharmacopoeia, and the drug market pays collectors six to eight cents a pound for the herb, pulled entire when in full flower and carefully dried.
Stems one to two feet high, weak, brittle, sparsely hairy, and swollen at the joints. Leaves large, thin, gray-green, once or twice pinnatifid, the segments deeply cut and scallop-toothed; petioles dilated at base and clasping the stem. Flowers in axillary umbellate clusters, the peduncles about as long as the leaves, the pedicels of unequal length; stamens many; style extremely short with two-lobed stigma; sepals two; petals four, bright yellow, arranged crosswise, each blossom about a half-inch broad. Pods smooth, one to two inches long, two-valved, opening at the base; seeds smooth, shining, dark brown, bearing on the side a white crest like a cock's comb. (Fig. 116.)
Destroy first-year leaf-tufts by hoe-cutting; prevent seed production in the second year by cutting the flowering stalks while in early bloom.