Flower:

1 or 2 short-stalked pea-shaped flowers in the upper leaf axils. Flowers are 3/8 to 1+ inch long, pink to purple (rarely white), the upper petal (standard) is broad, flaring up and notched in the center, the two lateral wings below it are oval shaped and often darker colored than the standard; they flank and obscure the lower keel underneath. The calyx holding the flower is usually minutely hairy with prong-like teeth about as long as the tube (see fruit photo below).

Leaves and stems:

Leaves are compound with 4 to 8 pairs of leaflets and a branched tendril at the tip that clasps surrounding vegetation for support. Leaflets are variable in shape, oblong-elliptic to lance-linear, ¾ to 1¼ inches long, 1/6 to 1/3 inch wide, sparsely hairy on the underside, often flattened or indented at the tip with a small, spine-like projection. A pair of leafy appendages (stipules) at the base of the compound leaf stalk are small and somewhat variable, with 2 or 3 pointed lobes, often with a small dark gland. Stems are angled, branched, ascending or climbing, and hairy to varying degrees, sometimes minutely so. 

Fruit:

Fruit is a flattened pea pod up to 2 inches long, producing 4 to 12 round beans. Pods ripen to light brown to black.

Notes:

Considered a crop and garden weed, Common Vetch has also been used as a green manure crop and for forage. It escaped cultivation, as many introduced species are wont to do. Ants seem to have a particular fondness for this plant, as it is common to find them nectaring at the gland on the stipule. While the leaves resemble a number of other vining members of the pea family, particularly American Vetch (Vicia americana), Common Vetch is distinguished from the rest by the short-stalked flowers and fruits single or in pairs in the leaf axils.

There are 2 subspecies, both of which may be found in Minnesota: subsp. nigra (formerly Vicia angustifolia or V. sativa var. angustifolia) flowers are usually less than ¾-inch long with a proportionately small calyx, pods ripen to black, and leaflets are narrow (1.5 to 6 mm wide) and more linear in shape, where subsp. sativa flowers are at least ¾ inch long with a proportionately larger calyx, leaflets are proportionately broader (4 to 10 mm wide) and more elliptic, and pods ripen to brown. Note that the leaflet shape can be variable even on a single plant, so sample both upper and lower leaves as well as multiple plants within a population. Distribution of the two within the state is unclear, but the majority of herbarium records are currently identified as V. angustifolia.