I should not want the quarried slate Or granite to perpetuate My memory when I am gone. It is not fit. I fought with stone Too long to have its weight upon The locked earth underneath whose sod I measure less than half a rod.
To know I was, may my bones be Tied to the anonymity Of hidden roots so intertwined The man I was becomes defined In one tall maple tree whose shade Falls gratefully where I am laid.
The speaker is thinking about his own death and deciding what he wants, and doesn't want, to be left behind. He rejects a gravestone of slate or granite. Stone, he says, is not "fit," because he has spent too much of his life fighting it. The line suggests hard physical labor, though the poem never spells out his work, so that's an inference. After a lifetime of struggle, he refuses to let a heavy slab press down on the ground above him, a grave he calls small, measuring "less than half a rod."
Instead, he imagines his body feeding the roots of a maple tree, so that "the man I was becomes defined" in something living. The mood is calm and quietly dignified, with no fear of dying. He prefers anonymity and growth to a carved name, and the tree's shade, falling "gratefully" over his grave, is the only memorial he wants.