Family: Fabaceae
Vicia villosa (hairy vetch, fodder vetch) is a legume native to parts of Europe and western Asia. It is often grown as a cover crop or green manure in agricultural settings. Farmers and gardeners often use hairy vetch as a cover crop in rotation with other crops, as it can improve soil quality by fixing as much as 200 lb/acre of atmospheric nitrogen. It is reported to be naturalized on all continents, and first was reported to be naturalized on Hawaiʻi in 1987. It is not currently regarded as a detrimental weed in the Hawaiian Islands, but is considered invasive in Alaska, Florida, Georgia, Kansas, Michigan, Minnesota, Oregon, and Washington state — as well as in Japan and some parts of Europe. It prefers temperate climates, which may only make it risky for planting at higher elevations on the Islands, where it is cooler.
High Risk Traits:
- Broad climate suitability (but predominantly grows in temperate climates)
- Naturalized on Hawaii Island and widely naturalized elsewhere
- A disturbance weed that may impact agriculture and the natural environment
- Other Vicia species are invasive
- Allelopathic
- Seeds reported to poison grazing animals (although foliage is palatable)
- Moderate shade tolerance
- Tolerates many soil types
- Smothering habit
- May also form dense cover that can outcompete and potentially exclude other species
- Reproduces by prolific seed production
- Annual reproductive cycle (reaches maturity in <1 year)
- Seeds dispersed ballistically as seedpods dry and dehisce, as well as a seed contaminant and through intentional cultivation
- Seeds may persist in the soil for 2+ years
- Tolerates mowing and grazing (i.e., mechanical control methods may be ineffective)
Low Risk Traits:
- As a predominantly temperate species, may only be a risk at cooler, higher elevations on tropical islands
- Not currently regarded as a detrimental weed in the Hawaiian Islands
- Unarmed (no spines, thorns, or burrs)
- Palatable forage plant (despite seed toxicity)
- Predominantly outcrossing (self-fertilization results in reduced seed set)
- Not reported to spread vegetatively
- Seeds are large and not readily dispersed
- Herbicides may provide effective control
