While his output covered a wide range of topics, he is best known for his contributions to botanical history, taxonomy, botanical bibliography, and botanical illustration. "Botanical Latin" (four editions 1966–1992), is his best known work, having become a standard reference and described as both the bible of plant taxonomists and a philological masterwork. It was begun during the war years and the first edition was basically a guide to Latin for botanists with no or limited knowledge of the language, which he described as a "do-it-yourself Latin kit" for taxonomists. Later, the work evolved into an etymological dictionary, but then Stearn learned that such a work had already been published in the Netherlands before the war. He then continued to expand it with the assistance of his wife and son, systematically collecting botanical terms from botanical texts. It is said that only he could have written this work, which explains not just the derivation of plant names but also the philological principles involved in forming those names. The work is considered responsible for the continued survival of Latin as the lingua franca of botany. In addition to this seminal text, he frequently delighted in the illumination that the classics could add to understanding plants and plant lore, such as his "Five Brethren of the Rose" (1965).