This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Perennial. Propagates by seeds. Time of bloom: July to August. Seed-time: August to September.
Range: Locally from Ontario to southern New York and Connecticut. Habitat: Fields, meadows, and waste places.
A showy plant, often cultivated in gardens for its beauty and becoming wild as an "escape." Stem often six feet or more long, smooth, angled, and broadly winged between the joints; the leaves also have winged petioles. Leaflets a single pair, broadly elliptic in shape, rather thick, strongly nerved, one to three inches long and a half-inch to an inch wide; tendrils short, with angled stalks, usually triple-branched; stipules large, lance-shaped, auricled at the base on the outer side. Flowers densely bunched or clustered at the end of a stiff, angled peduncle rising from the axils; they are about the size of Sweet Peas or even larger, but without fragrance, usually rosy pink in color but may be either purple or white. Pods one to three inches long, smooth, and many-seeded. These seeds, like those of the Meadow Pea, contain an alkaloid which makes them most unwholesome food for animals if eaten uncooked, causing a disease called Lathyrism, affecting the nervous and muscular systems and ending in paralysis.
Small areas should be grubbed out when first observed. Rankly infested ground should be put under cultivation of the most thorough kind. Seeding should be prevented by close cutting before the first flowers have matured, as the seeds have long vitality when in the soil.