Cow vetch (Vicia cracca)

Common Names: Tufted vetch, bird vetch, blue vetch, boreal vetch

Description:

Cow vetch (Vicia cracca) is a climbing, vining plant in the pea family, native to Europe and Asia and now naturalized across much of North America [1][4]. It was widely planted as a cover crop and livestock forage, and it has spread well beyond where it was sown [2]. MISIN tracks it because its weak, clambering stems can smother other plants and make it a real nuisance in prairie plantings and other disturbed, restored ground [2].

Habit:

Cow vetch is a sprawling, vining legume with weak stems that grow 2 to 3 feet long and clamber over other plants rather than standing on their own [2]. Each leaf is divided into many pairs of narrow, oval leaflets ? usually 8 to 12 pairs ? and ends in a thin, branching tendril that the plant uses to grab onto its neighbors [2][3]. Its stems are nearly smooth, with only a few short hairs [2]. From late spring into late summer it produces showy one-sided clusters of small violet-blue pea flowers, with as many as 20 to 50 flowers packed along a single stalk up to about 6 inches long [2][3]. After bloom it forms small, flat, brown, lance-shaped pods about an inch long [2].

It is easiest to spot in summer (about May through August), when the dense blue flower clusters stand out against roadsides, old fields, and the tops of other vegetation [2]. Outside the flowering season, look for the scrambling vines with many small paired leaflets and curling tendrils tangled through grasses and shrubs [2][3].

At-a-glance cues:

1. Weak, climbing vine, 2?3 feet long, sprawling over other plants [2]
2. Leaves divided into many (8?12) pairs of narrow leaflets, ending in a curling tendril [2][3]
3. One-sided clusters of many (20?50) small violet-blue pea flowers, summer-blooming [2][3]
4. Nearly hairless stems and small, flat, brown, lance-shaped seed pods about an inch long [2]

Leaves:

1. Arrangement: alternate along the stem; each leaf pinnately divided (leaflets in opposite pairs along a central stalk) [2][3]
2. Leaflets: usually 8?12 pairs, narrow and oval, with smooth edges [2][3]
3. Tendrils: each leaf tips in a thin, branching tendril used for climbing [2][3]
4. Surface: leaflets nearly smooth to lightly hairy [2]

Stems:

1. Habit: herbaceous (non-woody) climbing or trailing vine, weak-stemmed, 2?3 feet long, sprawling over other plants [2]
2. Surface: nearly hairless, with only a few short hairs [2]
3. Root: a deep taproot, roughly 1?3 feet long [3]

Flowers:

1. Color: violet-blue [2]
2. Shape: small pea-type (five-parted) flowers about ? inch long [2]
3. Arrangement: many (20?50) flowers crowded on one side of a long stalk (a one-sided raceme) up to about 6 inches long [2][3]
4. Bloom time: late spring through late summer (about May?August) [2]

Fruit and seeds:

1. Fruit type: a flat, lance-shaped pod (legume) about an inch long [2]
2. Color: brown when ripe [2]
3. Seeds: several small seeds per pod [2][3]
4. Dispersal: by seed; pods split to drop seed, which also moves with soil, machinery, and contaminated seed mixes [2][3]

Habitat:

Cow vetch is native to Europe and Asia and was introduced to North America, where it is now naturalized from southern Canada south through much of the United States [1][4]. Much of that spread traces back to deliberate planting ? it was widely sown as a cover crop, for green manure, and as forage for cattle, then escaped into the surrounding landscape [2][4].

It does best in open, sunny, disturbed places and tolerates dry, sandy soils [2]. Look for it along roadsides, in old and abandoned fields, in thickets and field edges, and in restored or replanted prairie ground [2]. It is a plant of disturbed and open habitat rather than shaded, intact forest [2].

Reproduction:

Cow vetch spreads mainly by seed [2][3]. The flat pods dry and split open to scatter seed near the parent plant, and that seed then travels farther in soil, on mowing and tillage equipment, and as a contaminant in forage or cover-crop seed mixes [2][3]. This is the main way it shows up in a new field or planting [2].

It grows as an annual or a short-lived perennial, sending down a deep taproot 1 to 3 feet long that helps it persist and resprout [3]. Plants leaf out and climb through spring, flower from about May into August, and set seed through summer [2][3]. For control, the key timing is to remove plants before the pods mature and shed seed [2].

Impact and Damage:

For homeowners and gardeners, cow vetch is mainly a smothering nuisance rather than a health hazard. Its weak stems climb up and over other plants, and a dense tangle can blanket and shade out garden plants, low shrubs, and patches of lawn edge [2]. It is not known for the skin irritation or pet-poisoning problems some other weeds cause; the trouble it brings is crowding, not toxicity [2].

For natural area stewards, cow vetch is a low concern in healthy, intact prairie but a genuine problem in disturbed and restored ground. State agency guidance notes it is not considered a threat to healthy native prairies at this time, but it can take over prairie reconstructions and disturbed sites, where its sprawling stems smother young native plantings before they establish [2]. Because it is a legume, it can also add nitrogen to the soil, which tends to favor weeds over the native plants adapted to leaner ground [2]. Catching it early in a new planting matters most [2].

Similar species:

Cow vetch is one of several climbing vetches, and they are easy to mix up where their ranges overlap. Its best marks are its nearly hairless stems, its dense one-sided clusters of 20?50 violet-blue flowers, and its flat brown pods [2][3].

Hairy vetch (Vicia villosa), also called winter vetch, is the closest match and grows in the same kinds of disturbed, open ground. It is told apart by its long, spreading hairs on the stems and leaves (cow vetch is nearly smooth), its flowers that are often blue-and-white rather than solid violet-blue, and its gray-to-black, hairy pods instead of cow vetch's flat brown ones [2][3].

American vetch (Vicia americana) is a native vetch that is easily confused with cow vetch and is worth keeping rather than removing. It is separated by its looser clusters of just a few (roughly 3?9) larger flowers, compared with cow vetch's crowded clusters of 20 or more, and by its generally smoother, less wiry growth [2].

Crown vetch (Securigera varia) is another sprawling, introduced legume often seen on roadsides and banks. It is distinguished by its pink-and-white flowers held in rounded, ball-like clusters, unlike cow vetch's blue flowers crowded along one side of a stalk [2].

Monitoring and rapid response:

Signs to watch for:

1. Weak, climbing vines with many small paired leaflets and curling tendrils, sprawling over other plants [2][3]
2. Dense one-sided clusters of small violet-blue pea flowers in summer (about May?August) [2]
3. Flat, brown, lance-shaped pods about an inch long forming after the flowers [2]

What you can do:

1. Pull or dig small patches by hand while the plants are young, before the pods form and shed seed ? try to lift the taproot so the plant doesn't resprout [2][3]
2. Bag plants that already have pods rather than composting them, since seed is the main way it spreads [2][3]
3. Cut or mow the vines before they flower to keep them from setting seed, repeating through the season as they regrow [2]
4. For natural areas, volunteer crews can focus on small outlier patches first and on protecting young prairie plantings, pulling or cutting before seed set over repeat visits [2]
5. Replant cleared ground with native cover ? agencies suggest native vetches such as American vetch, and other native legumes ? so bare soil doesn't simply refill with vetch [2]

When to call a professional:

1. Large or well-established infestations where hand removal cannot keep up [2]
2. Plantings where cow vetch keeps resprouting from its deep taproot or returning from the soil seed bank despite removal [2][3]
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. USDA NRCS PLANTS Database. Vicia cracca L. plants.usda.gov
2. Minnesota Department of Natural Resources. Cow vetch and hairy vetch (Vicia cracca, Vicia villosa). dnr.state.mn.us
3. University of Minnesota Extension. Cow vetch and hairy vetch. extension.umn.edu
4. Plants of the World Online (POWO), Royal Botanic Gardens, Kew. Vicia cracca L. powo.science.kew.org

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