This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Annual or winter annual. Propagates by seeds.
Time of bloom: June to August.
Seed-time: July to September.
Range: Eastern Canada and New England to the Dakotas, and southward to the Gulf of Mexico. Also on the Pacific Coast. Habitat: Grain fields, meadows, roadsides, waste places.
This is the Vetch most commonly grown as a forage plant, and as a weed it is often a survival of former cultivation by means of self-sown, dormant seeds. Also the seeds are sometimes sown as an impurity with grass and grain seeds, and in such places it makes itself a nuisance by entangling and pulling down the crop, making the harvest difficult. (Fig. 176.)
Stems one to three feet long, simple or branching from the base, hairy when young but later becoming smooth. Leaves pinnately compound, with broad, sharply toothed stipules and four to eight pairs of oblong leaflets, slightly notched at their tips and with midrib projecting as a fine, bristly point. Extending from between the terminal pair of leaflets is a long forked tendril. Flowers on short axillary peduncles, usually in pairs, nearly an inch long and rather showy, the corolla being reddish purple or sometimes rosy pink, the standard long obovate and notched at the top, the wings adherent to the curved keel. Pods slender, two to three inches long, hairy when green but becoming smooth, and slightly constricted between the small globular seeds as they ripen.
Prevent the development of seeds by early and close cutting. In grain fields, many of the young seedlings may be raked out with a weeding harrow when the crop is but a few inches tall. Or, later, but while still in the young and hairy stage, the weed may be destroyed by the use of chemical sprays.