He received his doctorate in sciences at the University of Louvain.

[1] Robyns spent two long stays at the Royal Botanic Gardens Kew, travelled in central Africa and performed taxonomic work on many groups of tropical African plants, amongst others: Rubiaceae, grasses and legumes.

[2] From 1931 to 1966 he served as director of the Jardin Botanique National de Belgique (National Botanic Garden of Belgium),[1] where he shaped the transfer of the institute from the site in Brussels to the Bouchout Domain in Meise.

He was the initiator of a monographic flora series for central Africa, still continued today ("Flore d'Afrique centrale").

From 1959 to 1964 he was president of the International Association for Plant Taxonomy.