Edna St. Vincent Millay crafted “Spring” as a free verse poem with 18 lines and no standard line length across a single stanza (a stanza collects a group of lines). As a free verse poem, “Spring” lacks the set meter (a measure of syllables) and rhyme schemes found in other poetic forms.

Millay most famously wrote sonnets, but “Spring” was one of her first free-verse poems. Free verse poems contrast with the older structured forms of poetry. For example, a poet writing a Shakespearean sonnet would have to ensure the first line rhymes with the third line, as the first stanza needs an ABAB rhyme pattern. While writing a free verse poem, the poet does not have to give up an image, word choice, or idea sequence to make it fit within the rhyme scheme or to match a rigid meter. Instead, the poem's contents arise organically and unhindered from the poet's mind.

Like free verse poems, Millay rejects literary tradition in “Spring.” She breaks the expectation of spring as a time of hope and renewal. The seemingly chaotic free verse poem mirrored the disruption people generally feel during mourning and the specific grief felt after World War I and the 1918 Spanish Flu pandemic.