The title helps unlock the poem. A hamadryad is a nymph in Greek myth who lives inside a tree, and here the speaker seems to watch one appear. The images blur woman and plant: "calyx" is the cup of a flower, her body is compared to young eucalyptus, and her "sinews" are slim like branches. She lies on a "narrow bed," which could be a bed of leaves, a bough, or something more human, and the poem lets that stay uncertain.
The speaker sounds hushed and admiring, almost afraid to break the moment. "How slim her sinews" and "How fresh the scent" read like quiet exclamations of wonder. The smells of violet and peppermint add a cool, clean sensuality. The mood is intimate and dreamlike, set in the "slow thought of eventide," with a night wood under ever-present stars. It feels less like a story than a single, held glimpse of something natural and beautiful that has chosen, briefly, to show itself.