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 biennial. Propagates by seeds.
Time of bloom: May to September.
Seed-time: June to October.
Range: Locally in most parts of the country, but most common in the southern states from Pennsylvania to Georgia. Habitat: Fields, roadsides, and waste places.
Hairy Vetch is frequently planted for a cover crop or for fodder, and is inclined to persist or to escape to roadsides and waste places. It resembles the Cow Vetch in form and habit, but is covered all over, stems, leaves, and even flower-stalks and pods, with persistent, long, soft hairs. Stems one to three feet long, with short, petioled pinnate leaves having lance-like stipules and twelve to twenty oblong leaflets, which are obtuse or varying to lance-shape or linear. Racemes three to six inches long, many-flowered, with rather short peduncles; the blossoms are violet and white, often nearly an inch long - almost twice the length of those of Vicia Cracca - with calyx-lobes bristly hairy on the lower side and the corollas not so slim, with standard and wings somewhat more spreading. The hairy pods contain six or eight small, dark, globular seeds.
Destroy winter plants by hoe-cutting or by surface cultivating of the ground, or they may be grazed off in early spring. Prevent seed development by cutting while in first bloom - and, if abundant, curing for hay. All waste-land and roadside plants should be destroyed.