There is an article on the main web page titled 'Echinacea Spent Blooms' that shows "a black coneflower plant". Probably similar to what you saw with the black zinnia blooms. Both coneflower and zinnia blooms were spent and turned shades of brown and black. Now... if you figure out a way to actually make the blooms start black..... you probably will be able to retire wnywhere you want!!!