What is crown vetch?

Crown vetch identification is simple in summer: look for sprawling, knee-high mats covered in round pink-and-white flower clusters, each shaped a bit like a small crown. It’s a perennial legume from Europe and western Asia that was planted on purpose for decades to hold soil on steep road banks.

Pennsylvania played a big part in that. A crown vetch selection called ‘Penngift’ was promoted here in the mid-1900s, and the plant went onto miles of highway slopes and mine reclamation sites. It does stop erosion, but it also spreads into fields, natural areas and yards and crowds out nearly everything else. PA DCNR now lists it as an invasive plant.

Crown vetch identification: what to look for

• Leaves: feather-like and compound, with about 7 to 25 small, oblong leaflets, each under an inch long, lined up in pairs and one at the tip. There are no tendrils.
• Stems: weak and sprawling, 2 to 6 feet long, piling on top of each other into a thick tangle.
• Flowers: pea-shaped, pink fading to white, packed roughly 6 to 25 into a rounded cluster at the end of a long stalk. Blooming runs from late spring through summer.
• Pods: thin, segmented pods that spread outward in a cluster like fingers, breaking into small one-seeded sections when ripe.
• Roots: deep and branching, with rhizomes that can run 10 feet or more and send up new shoots well away from the parent plant. Over a few years one plant can cover a surprising amount of ground.

Where it grows in Pennsylvania

Crown vetch is common statewide, especially along interstates, state routes and railroad grades, on steep road cuts, and on reclaimed strip mines. It favors sunny, well-drained slopes and handles poor, rocky soil.

Homeowners usually meet it where a lot borders one of those banks. It creeps in from the road right-of-way, climbs over shrubs, and takes over steep parts of the yard that are hard to mow.

Crown vetch look-alikes

• Hairy vetch and cow vetch have similar feathery leaves, but they end in curling tendrils that grab onto other plants, and their purple flowers line up along one side of a spike.
• Bird’s-foot trefoil has the same finger-like pods but bright yellow flowers and far fewer leaflets.
• White clover and other clovers have three leaflets per leaf, so they’re easy to rule out once you look closely.

How to get rid of crown vetch

Crown vetch is hard to eliminate because of its deep roots and rhizomes, and it usually takes several seasons. Before you start, think about the slope. If crown vetch is the only thing holding a steep bank in place, killing it all at once can leave bare soil to wash out in the next storm. Plan what will replace it, whether that’s a grass mix, native groundcovers, shrubs or a retaining wall.

Hand and mechanical:

• Small patches can be dug out, but you need to get the roots and rhizomes, and any piece left behind can resprout.
• Repeated mowing or string-trimming several times a season, starting in late spring, weakens the plants and stops seed production. It won’t kill an established stand on its own, but it keeps it from spreading.
• Mowing a clean edge between the bank and your lawn slows the creep of rhizomes into the yard.

Cultural: establish thick, competitive cover in its place. On gentler ground, a dense lawn mowed regularly will hold it back. On slopes, erosion-control blanket plus a seed mix suited to the site gets new cover going after the vetch is gone.

Herbicides: extension and conservation agencies report good results with triclopyr and clopyralid, which are selective for broadleaf plants and leave grasses mostly unharmed. 2,4-D can burn back top growth, and glyphosate works but kills any plant it touches. Treat while plants are actively growing, typically during bloom, then retreat regrowth later in the season and for a few years after. Near streams or wet areas, use only products labeled for aquatic sites. Read and follow the product label every time; the label is the law. Check that the product is labeled for your site, since lawn, bed and vegetable-garden products are not interchangeable. Applying herbicide for hire in Pennsylvania requires a PA Department of Agriculture pesticide applicator certification, so larger jobs belong with a licensed lawn-care or vegetation-management company.

Keeping it from coming back

Most crown vetch in yards comes in from a neighboring bank or right-of-way, so some regrowth along the edge is likely for years. Keep a mowed buffer strip, watch for runners each spring, and deal with them while they’re small.

Don’t plant it, and be cautious with older erosion-control seed mixes, which sometimes included it. If you keep horses, check pasture edges and fence lines and remove it there first.

Questions we get about crown vetch

Similar weeds

Bird's-foot TrefoilLotus corniculatusYellow SweetcloverMelilotus officinalisJapanese StiltgrassMicrostegium vimineum