The title says it all: the speaker is rooted, fixed in place like a tree. The poem opens with a dark oak, its leaves thick and full "as a suit," a odd, slightly formal comparison that makes the tree seem dressed up, solid, and a little grave. Then the poem turns inward. "My life in amber" suggests a life preserved, caught in a moment the way an insect is trapped in resin. Amber also comes from trees, so the image quietly links the speaker's life to the oak.
What the speaker feels seems mixed. Calling that life "greater than I am" hints at a sense of being smaller than one's own existence, perhaps overwhelmed by it or humbled. The last lines add a note of poverty and limit: there is something the speaker never gets past. The mood is still, hushed, and a bit heavy, both beautiful and confining. Being rooted brings steadiness, but it also means you cannot move.