The poem begins with a small, concrete scene: white-plumed reeds above yerba buena, a plant with a clear, dry smell. From there the speaker steps back and thinks about how richly nature is given to us, and how little he feels set apart from it. He says he was no more a part of it than "you," a "swift mindless carrier," which suggests he sees himself as something passing through, barely thinking.
What seems to matter most is desire. The speaker describes someone or something "so perfectly real / in wanting," and in that moment no thought felt deeper. Wanting, here, seems to outweigh any idea.
The ending turns quiet and a little rueful. The reeds return, now a "tassel," then a "keepsake / of no wisdom." The speaker holds on to a small token of the moment but admits it teaches him nothing. The mood is calm, spare, and gently uncertain, with short broken lines that mimic a mind drifting between image and thought.