This is Securigera varia, also known as Crown Vetch, and also referred to by the synonym Coronilla varia. This low growing aggressive vine is used in erosion control. It can cover a hillside and remain there for years although it is slow to grow in, once it takes hold it can crowd out all other plants so use this plant responsibly. The oil from this plant can be used as an insecticide. This is a larval host plant for the Wild Indigo Duskywing butterfly. It is also a nectar source for the Southern Cloudywing, Northern Cloudywing, and Atlantis Fritillary butterflies. USDA Hardiness Zone 4 to 10