"Fern Hill" is sparingly rhymed, with no more than one end rhyme per stanza. For example, “starry” (Line 3) and “barley” (Line 8), and “me” (Line 46) and “sea” (Line 54).

The length of the lines varies. The first two lines of each stanza, as well as Lines 6 and 7, are long. With just a few exceptions, each of these lines consists of 14 syllables, or seven poetic feet. The rhythm is iambic (an unstressed syllable followed by a stressed syllable), which means that the line is an iambic heptameter.

In all the stanzas, Lines 3, 4, and 5 are shorter than the first two lines, and Lines 8 and 9 are shorter than Lines 6 and 7. The shortest line in every stanza is Line 4, which comprises three feet, making the line an iambic trimeter. (There is one exception, Line 22, which is one syllable short.) In the trimeter of Lines 4 and 13, there is a variation in the iambic meter, since each of these lines begins with a trochee. A trochee is a reversed iamb—a stressed syllable followed by an unstressed one. Interestingly this substitution is with the word “Time,” which means this word stands out at the beginning of the line against the expected iambic rhythm.