The speaker imagines their own death and asks for something simple: to be remembered by a planted tree, ideally an oak. Rather than treating death as an ending, they picture it as a change of form. The oak stands for strength and endurance. It has deep roots, it outlasts the years, and it is "a force without a cage." Even when the wind shakes its branches, they seem to dance, while the roots keep it firmly in place.
That image carries the poem's comfort. The speaker wants to "live on" in the tree, rooted in the earth and still part of the world. The final lines are calm rather than sad: "I will not mourn the life I have lost," because becoming the tree feels like freedom. The mood is peaceful, hopeful and quietly confident. The steady rhymes and gentle rhythm add to that sense of ease, as if the speaker has already made peace with what is coming.