Crown vetch (Coronilla varia), a herbaceous perennial legume, has been used extensively in areas to control erosion or along roadways. The plant has escaped cultivation and become a serious invasive weed. Crown vetch grows in full sunlight or partial shade and spreads by utilizing rhizome roots that reach outward more than 10 feet. The stems of the crown vetch creep outward and can reach 6 feet in length. The plant seeds and spreads using its roots and has the capability of remaining dormant for 15 years. Because of the plant's aggressive spreading nature, planting crown vetch needs to be severely limited.
Burn areas of widespread crown vetch in late spring. Burn for three to four consecutive springs to effectively control crown vetch.
Mow crown vetch in June and August. Remove the flower heads before the plant produces seeds to help control the plant.
Spray crown vetch with the herbicide 2,4-D amine for spot control. Spray only the crown vetch and do so on a calm, windless day. Follow the directions on the herbicide label for application instructions.
Spray crown vetch in the spring with 1- to 2-percent solution of glyphosate mixed with water. Apply the herbicide only to the crown vetch because it will kill other plant life, too. Spray the plant in the spring using a garden sprayer. Repeat in the late spring and early fall if needed.
Apply clopyralid at a ratio of 0.25 percent with 0.5 percent surfactant to large infestations of crown vetch along roadsides or other areas. Distribute the clopyralid with a garden sprayer.