Multi-environment trial data of hairy vetch (Vicia villosa Roth.), including 50 environments in the United States and 35 lines screened for traits of interest to cover cropping. Environments are labeled as the unique combination of harvest year (‘19’ for the trials planted in the fall of 2018 and harvested in the spring of 2019, ‘20’ for those planted in the fall 2019 and harvested in the spring of 2020, ‘21’ for the trials planted in the fall of 2020 and harvested in the spring of 2021, and ‘22’ for the trials planted in the fall of 2021 and harvested in the spring of 2022) and the two digit abbreviation of the US state where the trial was located: Lockeford, CA (CA); Americus, GA (GA); Beltsville, MD (MD); St. Paul, MN (MN); Columbia, MO (MO); Caswell, Goldsboro, Kinston, Rocky Mount, or Salisbury, NC (NC); Mandan, ND (ND); Lincoln, NE (NE); Fallon, NV (NV); Varna, NY (NY); Ardmore, OK (OK); Corvallis, OR (OR); Knox City, TX (TX); Prairie du Sac, WI (WI); and Pullman, WA (WA). Environment details including latitude, longitude, soil type, soil taxonomy, planting date, and data collection dates are included in metadata. Lines were not consistently tested in all years. Some lines were dropped from low seed supply or poor performance in the trial. Other lines were added as they became available commercially or through breeding programs. Each line was grown in a single 4.57 m row, flanked by one or more rows of triticale (×Triticosecale Wittm. ex A. Camus [Secale × Triticum]). Triticale was used to simulate how growers typically plant hairy vetch in mixture with a winter annual grass. Distance between legume and triticale row varied between 19 and 76 cm, depending on environment (see details in [forthcoming Ag Data Commons ALT database citation]). Plots were planted with 0.66 g of vetch pure live non-hard seed per m, which was increased to 1.1 in 2020-2022 to improve stand uniformity and reduce variability in establishment. Planting depth varied between 1.3 and 3.8 cm. Entries were blocked four times in a randomized complete block design. Field data were collected using Field Book (Rife and Poland, 2014). Emergence was rated as a visual percent of plants emerged per plot one and two months after harvest. Emergence two months after harvest was used for analysis, unless snow or other factors prevented the collection of the rating two months after harvest, in which case emergence one month after harvest was used. Vigor was evaluated visually in the fall (one and two months after planting) and spring (once plants started actively growing after winter and at least two weeks prior to harvest) on a scale from ‘1’ to ‘9’, with ‘1’ representing the plot with lowest vigor in the trial, and ‘9’ representing the highest vigor in the trial. Spring stand was rated as a percent of the total plot with live plants after harsh winter conditions were over. Maturity was rated following a modified scale of Kalu and Fick (1981) at every harvest date. Biomass from each plot was harvested one to two times in the spring of 2019, 2020, 2021, and 2022, dried at 55ºC, then weighed. If two harvests took place, six to nine feet of each fifteen-foot plot was cut for each harvest. Biomass harvests were labeled “early” if the cover crop harvest timing happened around the typical planting time of earlier cash crops of a region (e.g. corn (Zea mays L) in the Southeast, conventional corn in the Midwest) and “late” if the harvest timing corresponded to planting time of later cash crops in a region (e.g. cotton in the Southeast, organic corn in the Midwest).