Her critical methodology included the work's historical context, the personal habits of the author, and the relationshop of the text to the time period. She prepared several editions of poetry by John Donne, including "The Divine Poems" (1952), "Selected Prose" (1967) and "The Elegies and the Songs of Sonnets" (1965), all of which she has been credited for her careful work. As a scholar of poetry by T. S. Eliot, she has written three studies on Eliot and has also said that the poet is a major influence on her own criticism. Gardner has also written criticism on John Milton and William Shakespeare. Gardner influenced the perceptions of many readers on British poetry, mostly such poetry from the late sixteenth to the early seventeenth centuries. Gardner was an Anglican Christian and her faith was a subtle part of her writing.