Hairy Vetch is an introduced and naturalized forb that grows either as an annual or a biennial. The stems branch occasionally and can reach to 3 feet long and are climbing but frequent found sprawling when there is little to climb on. Stems are green, round with ridges and with spreading hairs.
The leaves are pinnate with 5 to 10 pair of narrowly oblong leaflets each with a very short stalk. Leaflet surfaces and edges are hairy. The leaf tip has a branched tendril. The base of the leaf stalk has a pair of hairy stipules, lance-ovate in shape. Leaves are 5x as long as wide and can be up to 10 inches long. Each leaflet is about 1 inch long with an entire margin and a pointed tip that is the extension of the central vein of the leaflet.
The inflorescence is a long raceme, densely flowered on one side, of 10 to 40 stalked nodding flowers. The raceme arises from the leaf axil opposite a leaf and has a long grooved stalk.
The flowers are purplish but there is great variability from pinkish-white to blue-violet. They have a hairy greenish calyx whose base is swollen behind the point of attachment to the flower stalk, and has 5 hairy pointed lobes of uneven length - the lower 3 much longer than the upper 2 which look like one shallow lobe with a notch in the center. The corolla, free of hair, has typical pea structure with an upper larger standard (banner) petal, 2 side lateral petals that project forward, and 2 petals forming a keel. The side petals adhere to the keel petals. There are 10 stamens united into 2 groups of unequal length with a single style contained within the keel petals.
Fruit: Fertile flowers produce a 3/4 to 2 inch long smooth seed pod containing several round black seeds.
Habitat: Hairy Vetch grows from a rhizomatous root system in full or partial sun. Loamy soils are preferred but the plant is adventive and will occupy drier disturbed sites and can spread aggressively, particularly in cooler moist soils.
Names: The genus, Vicia, is the Latin word for pea-type plants. The species, villosa, means 'covered with soft hairs'. The author name for the plant classification, ‘Roth’ refers to Albrecht Wilhelm Roth (1757-18340 German botanist who published his research and was later associated with the University of Jena Botanical Institute.
Comparisons: The most confusing vetch in Minnesota will be Tufted Vetch, V. cracca, but there the base of the calyx is not swollen and the hairs on the stem are appressed, not spreading. V. americana, American Vetch, generally has more pinkish flowers, no swollen base on the calyx and the plant is not hairy. Veiny Pea, Lathyrus venosus, has a compact flower cluster, leaflets without stalks and only very short fine hair on the stem.
Above: 1st photo - The flowers are purplish but there is great variability from pinkish-white to blue-violet. 2nd photo - Flowers have a hairy greenish calyx whose base is swollen behind the point of attachment to the flower stalk.
Below: The inflorescence is a long, densely flowered on one side, raceme of 10 to 40 stalked nodding flowers.
Below: Leaves are pinnate with 5 to 10 pair of narrowly oblong leaflets each with a very short stalk. Leaflet surfaces and edges are hairy. The leaf tip has a branched tendril. The base of the leaf stalk (2nd photo) has a pair of hairy stipules, lance-ovate in shape. 3rd photo - The fruit is a 3/4 to 2 inch long smooth seed pod containing several round black seeds.
Notes: Like many aggressive introduced plants, Hairy Vetch was brought to North America for erosion control and cattle feed. Being a legume it fixes nitrogen in the soil. And again, like its now-unwanted brethren, it has few pest or disease problems. It is now found in all on the United States and most of Canada except the Prairie Provinces, the far north and Newfoundland and Labrador. The distribution in Minnesota is all on the eastern side of the state, from the Arrowhead down to the Metro Area and then south along the Mississippi River.
Hairy Vetch is one of five species of Vicia commonly found in Minnesota, all but one introduced. The native species is V. americana, American Vetch; the others are: V. angustifolia, Narrow-leaved Vetch; V. cracca, Tufted (or Bird) Vetch; V. sativa, Spring Vetch; and V. villosa, Hairy Vetch. Only the first is found in the Eloise Butler Wildflower Garden.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"