Common on greeting cards and dorm room posters, black-eyed Susans, known as an "aggressive perennial" (translation: a nuisance), are underappreciated. They bloom their hearts out from June to October--that's nearly half the year, folks!--and then, as the petals fade and fall, the center turns into a black gumdrop, suitable for Halloween. The seeds are beloved by finches and sparrows, so before you cut down the stalks you can watch nature provide for everyone. I'm thinking of letting them take over my garden.