This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Native. Perennial. Propagates by seeds.
Time of bloom: July to September.
Seed-time: August to October.
Range: New England to Minnesota, southward to Florida,
Louisiana, and Kansas. Habitat: Dry, sterile soil; pastures and thin meadows; thickets and open woods.
Cattle will eat this plant when it is young if there is no better forage, but it soon becomes hard and innutritious. Stems one to three feet tall, much branched, slender and spreading, sparsely hairy. Leaves few and rather small, pinnately three-foliolate, the leaflets a half-inch to two inches long, thin, oblong or elliptic, bristle-tipped, finely appressed-hairy on the under side; petioles often scarcely longer than the footstalk of the middle leaflet. Flowers in small axillary clusters on very slender peduncles much longer than the leaves; corolla violet-purple, about a quarter-inch long, the keel often longer than the standard. Pod ovate, pointed, flattened, net-veined, about a sixth of an inch long, containing one seed. (Fig. 175.)
Cut before the earliest flowers mature seeds.
Cultivate and liberally fertilize the ground, reseeding it with clovers of a better quality which will smother the growth of this weed from dormant seeds.