The Giving Tree by Shel Silverstein, is about a tree who loves a boy unconditionally. As the boy grows up, he visits the tree less and less. When the boy does visit the tree, he only goes to ask for help. Although the tree has little to give, she gives the boy all that she has until she has nothing left but her love for the boy.
I would use The Giving Tree for a lesson on character education integrated with science. Two activities that students can do are write a letter to a person whom they appreciate and label the parts of the tree from the story and how the boy used them or how they would use them. The LEXILE reading level is 530L.