"I am the autumnal sun" is a startling first line. The speaker does not say "I watch the sun" or "I feel like autumn." He simply says "I am." The six lines of prose-like verse before it explain how that is possible. Sometimes, Thoreau writes, "a mortal feels in himself Nature," and it is the Mother, not the Father, who "stirs within him." Nature is imagined as a bodily presence, and the image gets oddly physical: "some globule / from her veins steals up into our own." Her blood, or her sap, seeps into ours. The verse that follows reads like the result of that exchange, a person speaking in the voice of a season.
That voice is not triumphant. The prelude promises that a mortal "becomes immortal with her immortality," but the sun who speaks is running out of time: "With autumn gales my race is run." The poem sets human feeling against a natural cycle, and the human feeling is mostly sadness at being near the end of the year.
The form changes as the poem moves from one part to the other. The opening is unrhymed and loose, closer to thoughtful prose than to song. Once the sun speaks, the poem settles into rhyming couplets: *sun/run*, *flowers/bowers*, *moon/mid-noon*, *woods/moods*, *leaf/grief*. The rhythm is mostly a light, tapping beat of about four stresses to a line. "With autumn gales my race is run" is almost perfectly regular, which gives it the feel of a closing sentence. Other lines stretch. "When will the hazel put forth its flowers" runs long and slows down, as if the sun were pausing to look around at what has not happened. Then comes the compact "I am all sere and yellow, / And to my core mellow." The rhymes here are two-syllable and soft, and they end on a sound that trails off.
The imagery turns the sun into something between a star, a tree, and an aging person. It owns "bowers" and "woods," and it asks questions that sound like an anxious gardener's: when will the hazel flower, when will the grape ripen? These are questions about fruitfulness, asked by someone whose strength is fading. Then it asks for the "harvest or the hunter's moon" to "turn my midnight into mid-noon." Judging by the imagery, the sun's own light is shrinking, so it hopes for a brighter moon to make up the loss. The wish is touching because it is a little desperate.
The phrase "sere and yellow" is an old, familiar way of describing withered leaves, but the next line complicates it. To be "to my core mellow" is to be ripe, softened, sweet like fruit. Decline and fulfilment are folded into one image. That is why the poem's grief does not feel simple. The speaker is both finished and complete.
The last four lines move the season indoors. The mast, meaning fallen nuts, is "dropping within my woods," and "the winter is lurking within my moods." The repeated "within" matters. Woods and moods rhyme, so landscape and psychology are tied together at the ear as well as in the meaning. Winter is not approaching from outside; it is already inside, and "lurking" makes it sound like an animal waiting. Even the sounds around the speaker become part of his mind: "the rustling of the withered leaf / Is the constant music of my grief." Here the dry leaves are not just heard, they are taken in as music. The closing ellipsis leaves the thought unfinished, as though the sound simply goes on.
The poem is significant because it shows, in a small space, an idea that runs through Thoreau's writing: a person is not standing outside nature, taking notes. Walden, his best-known book, follows a year through its seasons, and this short piece compresses the same attention into a few lines. Its sadness is not self-pity, because the speaker has handed his grief over to a sun and a wood and a heap of dry leaves. By the end, we are not sure where the season stops and the person begins, and that is the poem's quiet achievement.