During Stearn's initial four years in Cambridge (1929–1933), he published twenty-four papers, predominantly in the Gardeners' Chronicle and Gardening Illustrated and the Journal of Botany,[1][9] his first in 1929. While working as a gardener's boy during school holidays he had observed a specimen of Campanula pusilla (Campanula cochleariifolia) with a distorted corolla. He then described and published the first appearance of the causative agent, the mould Peronospora corollaea, in Britain, using the facilities of the Botany library.[8][69]