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The book follows the life of a female apple tree and a boy who are able to communicate with each other; the tree addresses the human as "Boy" his entire life. In his childhood, the boy enjoys playing with the tree, climbing her trunk, swinging from her branches, and eating her apples. However, as time passes he starts to make requests of the tree.
After entering adolescence, the boy wants money, and the tree suggests that he pick and sell her apples, which he does. After reaching adulthood, the boy wants a house, and the tree suggests he cut her branches to build a house. After reaching middle age, the boy wants a boat, and the tree allows him to cut her trunk to make a boat, leaving only a stump. Each such stage of giving by the tree ends with the sentence "And the tree was happy."
In the final pages, the boy (now an old man) meets the tree once more. The tree sadly states she has nothing left to give, as her apples, branches, and trunk are gone and only a stump remains. But the boy wants only "a quiet place to sit and rest," which the stump can provide. This final stage of giving, and the entire story, end with the sentence "And the tree was happy."