Here's why:
* Tells a story: The poem narrates the relationship between a boy and a tree over time. It follows a clear timeline, from the boy's childhood to his adulthood.
* Characters and dialogue: The poem features two main characters, the boy and the tree. Although the tree doesn't speak, the boy's actions and the tree's changes tell a story.
* Plot and Conflict: There's a clear plot: the boy uses the tree for various things throughout his life. The conflict lies in the boy's growing need for things and the tree's dwindling ability to provide.
* Theme: The poem explores a theme of the cyclical nature of life and the importance of giving and receiving.
While the poem has elements of other types (like the emotional impact of a lyric poem or the simple, direct language of a free verse poem), its primary structure is that of a narrative.