Bean family (Fabaceae)
Description: This introduced annual or biennial plant is 1–3' tall, branching occasionally and having a tendency to sprawl. The round stems have spreading white hairs and conspicuous ridges. The alternate compound leaves are up to 10" long and 2" across, consisting of 8-12 pairs of leaflets and a terminal tendril that clings to adjacent vegetation for support. The central stalk of each compound leaf has spreading white hairs. The leaflets are up to 1" long and ¼" across. They are oblong, oblong-lanceolate, or linear, and have smooth margins with small pointed tips. There are usually scattered white hairs across the lower or upper surface of the leaflets. Slender racemes of flowers up to 6" long develop from the axils of the compound leaves. The stalks of these racemes are covered with spreading hairs and often turn purple toward their tips. The one-sided racemes consist of 5-20 pairs of nodding flowers. These flowers vary in color from pink to blue-violet, depending on the strain or local ecotype. Each tubular flower is about ½–¾" long, consisting of 5 petals and a hairy calyx that is united at the base. Aside from its long tubular base, the flower has a typical pea-like structure, consisting of a standard, keel, and 2 side petals. The upper petal forming the standard is usually a darker shade of color than the remaining petals. The tubular calyx varies in color from green to purple and has hairy teeth. The lower teeth of the calyx are much longer than the upper teeth. The swollen base of the calyx protrudes behind the apex of the pedicel, rather than originating directly from it. The blooming period usually occurs from early to mid-summer and lasts about 1-2 months, although some plants may bloom later in the year. Each flower can produce a flat-sided seedpod that is up to 2" long and contains several round seeds. The root system produces rhizomes, enabling this plant to form vegetative colonies.
Cultivation: Full or partial sun, moist to mesic conditions, and fertile loamy soil are preferred, although sometimes this plant is found in drier locations, such as slopes. It does well in grassy areas, because the blades of grass provide support for the tendrils while admitting sufficient sunlight for the leaves. Like many other introduced vetches, Hairy Vetch can spread aggressively.
Range & Habitat: This is a common plant in many areas of central and northern Illinois, but it is less common in southern Illinois (see Distribution Map). Official records probably underestimate its actual occurrence within the state. Hairy Vetch was introduced into the United States from Europe as a forage crop for livestock. Habitats include moist to mesic black soil prairies, grassy meadows along rivers or in woodlands, banks of rivers, shoulders of highway overpasses, areas along roads, edges of cropland, and abandoned fields. Sometimes this plant becomes an agricultural pest and invades fields, and it can also successfully compete against native plants in natural habitats. While Hairy Vetch forms colonies, they are not dense enough to exclude other species of plants, unlike the colonies that are formed by Coronilla varia (Crown Vetch).
Faunal Associations: The nectar of the flowers attracts long-tongued bees primarily, especially bumblebees. Less common visitors include butterflies and skippers. The caterpillars of the some butterflies and moths feed on vetches and other legumes, including Glaucopsyche lygdamus (Silvery Blue), Colias eurytheme (Orange Sulfur), and Caenurgina chloropha (Vetch Looper Moth). Insects feeding on the seeds or seedpods include Acanthoscelides spp. (Bean Weevils) and Pitedia persimilis (Stinkbug sp.), while Epicauta fabricii (Blister Beetle sp.) feed on the foliage and flowers. There are scattered reports of upland gamebirds eating the leaves or seeds of vetches to a limited extent, including the Ruffed Grouse, Wild Turkey, and Ring-Necked Pheasant. The foliage of Hairy Vetch is palatable and can be eaten by mammalian herbivores, although there have reports of cattle being poisoned after feeding from bags that contained seeds of Hairy Vetch.
Photographic Location: A moist black soil prairie remnant along an abandoned railroad in Champaign County, Illinois.
Comments: Hairy Vetch has attractive flowers in long racemes, usually in off-shades of pink or blue. There are several Vicia spp. (Vetches) that occur in Illinois, although botanists disagree among themselves over the exact number. For example, several varieties of Hairy Vetch have been identified, but Mohlenbrock (2002) considers some of these varieties to be distinct species. Hairy Vetch can be distinguished from other vetches by the presence of spreading hairs on its stems, the large number of flowers on its racemes (5-20 pairs), and the shape of its calyx (lower teeth much longer than the upper teeth; a swollen base that protrudes behind the pedicel). Some vetches with a similar appearance to Hairy Vetch include Vicia cracca (Cow Vetch) and Vicia dasycarpa (Smooth Vetch). However, Cow Vetch is a perennial plant that has appressed hairs on its stems and the calyx of its flowers doesn't have a protruding swollen base. Smooth Vetch is virtually identical to Hairy Vetch, except that it is largely lacking in hairs of any kind. This latter species is sometimes considered a variety of Hairy Vetch.