Final answer:
The pomegranate tree in Hassan's letter to Amir symbolizes the once thriving but now withering relationship between the two characters, mirroring the decay and loss within their personal lives and Afghanistan.
Step-by-step explanation:
In the letter to Amir, the pomegranate tree that once bore fruit but now has not for years serves as a powerful symbol for the withering relationship between Amir and Hassan. Just as the tree no longer produces fruit, their friendship and connection have deteriorated, failing to yield the camaraderie and closeness that they once shared in their youth. This image reflects the broader themes of loss and the impact of time on both relationships and the characters' personal lives against the backdrop of a changing Afghanistan.