Trying any stain remover on a different piece of fabric that you've stained with the flowers sounds like a good idea. I'd go with synthrapol, or Oxi Clean, as suggested above, or try Goo Gone Stain remover. But again, because of the ivory fabric, I'd try on a separate test piece (similar in color as you don't have any more), just to be sure whatever you use doesn't take the color out totally.