Plum Tree (Symbol)
While the speaker mentions a number of different sorts of plant life in the first half of the poem, the plum tree is the central symbol in her backyard. It functions as a symbol of the happiness she has lost after her husband's death. It blooms spectacularly and the spectacle of it only reminds the speaker of the previous springs that she used to share with her husband. Its blossoming this year fails to bring her the joy it used to, because it carries an association that has become painful.
White Flowers (Symbol)
In the poem's final lines, the speaker imagines falling into a patch of marshland near a tree of white flowers. In the context of the piece, these white flowers symbolize the speaker's acceptance of circumstance. Unable to appreciate the beauty of spring in her old way, she chooses to imagine this act of sinking and falling as her only means of appreciating what is around her. While this action can be read as defeat or despair, given the speaker's expressed desire to fall into these flowers, it is also reasonable to take it as an acceptance. The white flowers symbolize an acknowledgment of grief, suggesting there might be a way forward, however painful.
