In 1933, H. R. Hutchinson, who was the Librarian at the Lindley Library, Royal Horticultural Society's (RHS) in London, was due to retire. John Gilmour, now assistant director at the Kew Gardens, put forward Stearn's name, together with Bowles, a vice-president of the Society, who had discovered Stearn at the bookshop. Stearn was 22 when he began work at the library, initially as assistant librarian, before taking over Hutchinson's position after six months. He later explained his appointment at such a young age as being the result of World War I: "All the people who should have had those jobs were dead." There he collaborated with Bowles on a number of plant monographs, such as Bowles' "Handbook of Crocus" and their work on "Anemone japonica" ("Anemone hupehensis" var. "japonica"). Written in 1947, it is still considered one of the most comprehensive accounts of the origins and nomenclature of fall-blooming anemones. Stearn was one of the last people to see Bowles alive, and when Bowles died, Stearn wrote an appreciation of him, and later contributed the entry on Bowles to the Oxford Dictionary of National Biography. Much of his spare time was spent studying at the Kew Gardens.