Crown vetch (Coronilla varia) is an excellent plant to grow as a ground cover and for erosion control. It has rhizomes, underground stems, which can grow as long 10 feet, making it quite difficult to dig up. If you no longer need or want your crown vetch or if it has invaded other areas of the garden or yard, you may have found that getting rid of it is not easy. Fortunately though, with the right technique and some patience, you may finally be able rid your garden or yard of the unwanted crown vetch.
Apply an herbicide, such as one labeled "2,4-D," to the crown vetch. If the crown vetch is near other plants, paint it on with a paintbrush so you don’t kill the other plants. Repeat as you notice the crown vetch growing again. Always adhere to the dosing and application directions that are printed on the label.
Purchase a roll of thick black plastic and spread it out over all the area where the crown vetch is located. Secure it with stakes or heavy objects such as bricks. This method works well for large patches of crown vetch and if the herbicide was ineffective at killing your crown vetch.
Leave the plastic there for at least 60 days. Everything underneath should die and the soil should be sterilized.