Please help me identify this plant, growing along the rural roadway in mountainous eastern WV. Rocky soil, mountain laurel and Virginia pine are plentiful -- and then this, seems to be spreading or reseeding in steep areas. Am guessing it's some sort of vetch family by the foliage; would love to transfer some to start on a recently graded steep hill near my new construction, but no idea if it is native -- or if it will transplant successfully.