My black eyed Susan's flower petals have turned green on some plants. Do I need to fertilize them?
Black Eyed Susans
Your plant appears to be suffering from "aster yellows". It is an infection typically spread by leaf hoppers. If you are within a month of your first frost, I'd cut the plant to the ground and make sure every bit of it is tossed out. It might be a mite, too. Here is comprehensive info: http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/diseases/viruses/aster-yellows.aspx