Not as well that the metaphor is complex in that various other elements are added to it. It becomes evident as we read the poem that nature is also a process leading towards death, as well as life. The poet is suggesting that the same force that gives life, and death, to the flower also drives him. There is a strong sense of incipient death in the images of the poem. The poet is aware that as flowers and trees die naturally over time, so will he.
Nature is also the destroyer as well as the creator.
Note that in the last line that the poet is comparing the life of a human being to the growth and decline of a tree. The same thing that bends the tree or flower causes old age and finally death in the human being. Through a comparison that is very subtly brought about between nature and human life, the poet creates the poem as a long, continuous metaphor. The very life force that drives nature also gives the human life. In other words the force of life and death that is in the flower is also in the human body.