September can be lush with flowers, if you choose the right plants:
Chelone (Turtlehead) zones 5-9
A unique name and an easy plant to grow. The pink flowers are shaped like a turtle's head supposedly.
This plant grows 24" to 36" tall and wide in a lush stand, covered in the unusual pink blooms. Can tolerate wet soil and will grow pond side or stream side, but will also thrive in your well drained perennial border. Victoria has this one in her own yard, and the flowers really brighten up the fall garden.