Symbolism, Imagery, Allegory
When Whitney first starts growing herbs as part of her eating disorder treatment, she thinks the task is stupid and useless—she plants the seeds without much enthusiasm and doesn't even seem to care if they grow. But slowly the plants start sprouting and Whitney starts caring about them. She begins to nurture and help them to grow more:
But there was something I liked about the idea of those seeds, buried so deep, having at least a chance to emerge. Even if you couldn't see it beneath the surface, molecules were bonding, energy pushing up slowly, as something worked so hard, all alone, to grow. (9.218)
The herbs represent Whitney's growth and recovery—and Annabel's too. It doesn't happen quickly or overnight for either sister, and it requires effort and patience, but both girls start to recover from their trauma and slowly emerge. They grow stronger and begin to create new lives for themselves, even if they didn't think that was possible at first. Just like the herbs, they keep growing.