Answer: It's often best to plant perennial wildflower seed in the fall, since that's nature's way. Often these seeds require some stratification, (exposure to cool, moist conditions for a period of time) in order to germinate. This is true for Black-Eyed Susans (Rudibeckia). You can plant them in spring, too, but you'll need to pretreat seeds by refrigerating them in a plastic bag with moistened growing medium (like seed-starting soil) for a couple of weeks. Enjoy!
Q&A Library Searching Tips