Crown vetch, Coronilla (syn. Securigera) varia, in the Legume Family, a native of Eurasia and North Africa, has been used for a number of years as a roadside and freeway plant to control erosion. Although it does that job very well, it is extremely invasive, and once established is almost impossible to eradicate. It forms a heavy, creeping mat that spreads and out-competes other vegetation.
Its clusters of pink, clover-like flowers are deceptively attractive, as is the fern-like foliage, but it is like amercian vetch on steroids. Rogue it out as soon as you encounter it, or it will take over your garden.
The first time I saw Crown Vetch was in the late 1960's when we were seeking plants to landscape Milwaukee freeways. We planted a patch to see if it was hardy. Boy, was it ever! It is now listed as an invasive plant in Wisconsin and many other states.