Crown Vetch [Securigera varia] found at Fletcher Park on 1 June 2013. It’s a member of the Pea (Fabaceae) family. Newcomb’s Wildflower Guide, pages 66-67, states “it’s a sprawling plant of roadsides, extensively planted as a ground cover for steep banks” and lists it as Coronilla varia. These flowers were on the border of a field that was in the process of being plowed.
USDA Plants Listing: Securigera varia