Burns spends two-thirds of this song on a scene before he says a word about people. We stand at the edge of a cornfield at dawn, on a "bawk" (the Scots word for a strip of ground left between fields), where a rose-bud bends its "thorny stalk" so "gently" that the thorns almost disappear. The adverb does a lot of work. It makes the flower seem aware of its own delicacy, as if it were being careful. The colours and weights come next: "crimson glory," a head "drooping rich" with dew, and a scent that fills the air. Everything is heavy with moisture and about to open.
The second stanza moves a few inches into the bush, where "her covert nest" hides a linnet. Here the dew is no longer decoration. It "sat chilly on her breast," and the verb "sat" makes the cold feel settled and patient, like the bird. She is "fondly" pressed over her eggs, and that word turns discomfort into love. The stanza ends by looking ahead to the "tender brood" who will "Awake the early morning," so the mother's cold vigil is the price of a future chorus of birdsong.
Only in the last stanza does the poem reveal why it has been showing us all this. The turn comes in the words "So thou." The linnet and the rose-bud become comparisons for a girl named Jeany. She is the "dear bird" who will "sweetly pay the tender care" of her parents with "trembling string or vocal air," meaning music, and she is the "sweet Rose-bud" who will "beauteous blaze upon the day." The comparison is gentler and more unusual than a plain compliment to a pretty girl. The poem is largely about the people who watched over her, and her beauty counts as repayment of a debt. The final image of the "parent's evening ray" that "watch'd thy early morning" gives the whole poem a quiet shape. Her morning is the parents' evening, and the poem seems to know that the two are linked. That is an inference from the sun imagery, but the contrast between "early morning" and "evening" is hard to read any other way.
The form helps this feeling of calm. Each stanza has eight lines, rhymed in two groups of three with a short closing line in each: walk, bawk, stalk, then fled, spread, head. Every fourth line ends on "morning," so the word comes back like a refrain. Burns changes what precedes it each time: "dewy morning," "early morning," "Sae early in the morning," and finally "That watch'd thy early morning." The word keeps returning while its meaning shifts from a time of day to a stage of life. The longer lines are tidy four-beat lines ("A ROSE-bud BY my EARly WALK"), and the shorter refrain lines end on a soft, unstressed syllable. That gives each stanza a little sigh at the end, which suits a text that calls itself a "Song."
The language is a mix of Scots and English. "Sae," "o'," "a'," "amang," and "tents" (meaning "tends" or "takes care of") sit beside more literary-sounding words like "adown" and "covert." The mix keeps the poem rooted in a real Scottish field while letting it sound graceful. "Tents" is especially well chosen, because it makes care sound like an ordinary, practical job, which is how parental love often looks.
The poem matters because of how much it does with so little. Its subject is slight, a compliment to a young girl, yet it turns the compliment into a small philosophy of growing up: beauty and talent are things you are given by others, and the right response is to blossom and sing. A shivering bird and a dew-heavy flower carry that idea without any lecture. Burns also lets the freshness of the images do the persuading, so a reader can enjoy the song at first reading and notice the sadness of that "evening ray" later.