“Fern Hill” was written in 1944 and published in 1946 in Thomas’s book Deaths and Entrances. It was written during what critics consider the last period of Thomas’s career, in which he concentrated on longer narrative poems with vivid imagery. It resembles the style of the Romantic poets, and, like many of Thomas’s works, is heavily influenced by nature. The poem is named for the farm of Thomas’s aunt, and Thomas likely drew on his own life while writing it.
The poem takes the form of six stanzas with nine lines each, each of which follows the same pattern of the number of syllables in each line. Rather than conventional rhymes, the poem employs slant rhymes based on assonance, or shared vowel sounds, with each verse following the pattern abcdeabcd. For example, in the first stanza, there is assonance between "boughs" and "towns," "green" and "leaves," "starry" and "barley," and "climb" and "light."