Horseshoe Vetch

I always get confused between Horseshoe Vetch and Common Bird's-foot-trefoil. With care, I can separate them, but I always have to check. Horseshoe Vetch flowers do tend to have feint reddish lines leading along the length into the "mouth" whereas Common Bird's-foot-trefoil flowers are bigger and have no lines, althought the buds are reddish before the flower comes out.

See Common Bird's-foot-trefoil