Crown vetch is a pretty plant if you look at it from a distance. With its soft, feathery leaflets and purple flowers, it seems innocuous at first glance, but underground it spreads rhizomes like a thick mat, choking out other plants as it moves in. If you want to kill crown vetch before it invades your yard, be ready for a fight, as it is a hardy plant.
Things You'll Need
- All-purpose herbicide for broadleaf plants
- Weed mat
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Spray the crown vetch with an all-purpose herbicide, which will kill the upper plant within a few days. However, the perennial vine has rhizomes for roots, and they may not die after the first application. Spray any new shoots that emerge. Crown vetch seeds are viable in the ground for up to 10 years, so you may have to spray over several growing seasons.
Dig up the rhizomes using a shovel. Place them in a wheelbarrow and then either put them in a plastic trash bag for throwing away or give them to a neighbor who has an erosion problem to conquer. Don't expect to get every little piece; it is likely you will miss a few or that some will break apart since they can get up to 10 feet long. You will see some new shoots popping up here and there. Either dig them up again or revert to spraying with herbicide.
Burn the field or slope if your county allows burning and with their permission. The fire is an efficient way to burn off the plant and seeds above ground when you have large areas to control and if there is grass growing in combination with the crown vetch. Without a plant to provide photosynthesis, the rhizomes will eventually shrivel up and die.
Mow the patch of crown vetch as low as you can to the ground during the heat of summer. It is slow to respond if it has lost most of its growth. Combine this treatment with a herbicide and you will make great progress in killing back the crown vetch. Start new plants to prevent erosion, and spread weed mat and thick mulch to prevent regrowth.
Eradicate any new signs of growth every year with the combination of all of the above steps. Do not let any areas just go to weeds or the crown vetch will strengthen itself by growing new healthy rhizomes and spreading over the area you just finished killing off.