Symbolism, Imagery, Allegory
After having seriously wronged Helen by raping her in the park, Frank continues to linger in and around the store. He feels terrible about his actions and wants to make amends, but he doesn't seem to realize that his continued presence causes additional pain.
He makes her a wooden flower as a gesture of his sorrow and leaves it in her mailbox. He sees that she takes it, but it doesn't have the desired effect:
The wooden flower reminded Helen of her unhappiness. She lived in hatred of herself for having loved the clerk against her better judgment. (7.11.11)
Frank later finds the flower he gave her in the trash. At the end of the story, Frank imagines St. Francis taking the wooden flower out of the trash, transforming it into a real flower, and giving it to Helen as an expression of Frank's love and best wishes.
This doesn't actually happen. The flower remains something in the trash, something made of dead wood, not something alive. Helen forgives Frank, but we don't get the impression that they get back together. It takes more than a flower to heal such deep wounds.