5 Flowers You Plant Once and Never Buy Again! Black-Eyed Susan Black-Eyed Susans are hardy and easy to grow. Once planted, they often return with bright cheerful blooms. Marigolds Marigolds grow quickly and naturally drop seeds. This helps new plants grow in future seasons. Coneflower Coneflowers are strong, long-lasting flowers. They can reseed themselves and bloom year after year. | Thayer Cruz