After his return to London in 1946, at the end of the Second World War, a number of major publications ensued, including "Lilies of the World" in 1950. The RHS also imposed two major tasks on their librarian. In 1950, Frederick Chittenden, a previous director of RHS Wisley and Keeper of the Library, died leaving unfinished the four volume RHS "Dictionary of Gardening" that the society had commissioned from him before the war. The war had interrupted the work as many of the expected contributors were unavailable. Stearn, together with Patrick Synge, the RHS Publications Editor, undertook to complete the work, particularly volume IV (R–Z), a task he completed within six months, with 50 new articles. The finished work was published in 1951 and not only did he undertake the role of editing this large work but his contributions covered 50 genera, 600 species and complex identification keys such as "Solidago" and "Viola". Since Stearn's entries in volume IV extended from "Soldanella" to "Zygotritonia", he would jest that he was but "a peculiar authority on plants from 'So-' onwards". He issued a revised version in 1956 with Synge in which he added a further 86 articles. His recollection of this task was that he acquired "that occupational hazard of compilers of encyclopaedias", encyclopedic knowledge.