Final answer:
The detail from the poem that suggests the tree is selfless and giving is when it offers to send the person to its brother who can provide the desired red rose. The tree is willing to sacrifice its own roses to help fulfill the person's request.
Step-by-step explanation:
The detail from the poem that suggests the tree is selfless and giving is when it offers to send the person to its brother who can provide the desired red rose. This shows that the tree is willing to sacrifice its own roses to help fulfill the person's request. The tree's response also describes the beauty of its roses, emphasizing its generosity and willingness to give.