Time of bloom: June to August.
Seed-time: July to September.
Range: New Brunswick, Maine, Massachusetts, New York, and Ontario.
Habitat: Locally in fields and waste places.
This plant is accounted a worthless and troublesome weed throughout Europe and Russian Asia, and, since the areas where it has established itself in this country are as yet few and small, it would be well to keep it from wider dissemination, or even to stamp it out in as many of these restricted localities as possible. Like other plants of the genus Lathyrus, it is poisonous to grazing animals when eaten in any considerable quantity, especially when seeding; and persons who have eaten the seeds have suffered with violent headache and nausea.
Stems one to three feet long, weak, slender, angled and branching. The pinnate leaves consist of two bright green, narrowly lance-shaped leaflets, smooth and pointed at both ends, a long, curling tendril extending between them; stipules large, long-pointed, and leaf-like, auricled at the base on the outer side. Racemes axillary, on peduncles much longer than the leaves, bearing four to nine bright yellow blossoms about a half-inch long with broadly obovate standard and wings nearly equaling it in length. Pods a little more than an inch long, slender, thin, and smooth, containing many small, dark, globular seeds.
Prevent development of seed by cutting repeatedly during the growing season, which will also starve the perennial roots. Small areas should be hand-pulled or grubbed out. Ground too rankly infested to be cleansed by land-labor should be put to some crop requiring very close cultivation.