In 1930, he accepted an offer to work in the Colonial Office in Northern Rhodesia (now Zambia), where he collected plants for herbarium specimens.
He was based at Matonchi Farm, west of Mwinilunga, North-Western Province, Zambia, near the borders of Angola and the Democratic Republic of the Congo for 4½ months.
[2] He discovered many new species, and several were named after him,[3] including Commelina milne-redheadii Faden (Commelinaceae).
[4] In 1949, he and others began the process to establish an “Association pour l’Etude Taxonomique de la Flore d’Afrique Tropicale” (or “Association for the Taxonomic Study of the Flora of Tropical Africa”) (AETFAT).
He prepared treatments for the Flora of Tropical East Africa and eventually published 161 new names.