Bergmans had access to a broad and efficient network of experts.
One of his most important contacts was architect and later his father-in-law Jan Visser (1875-1946), and especially his daughter, Bergmans’ future wife, Coby, who had trained at the Huis te Lande horticultural school. Bergmans was a member of professional associations like the Society for Dutch Garden Architects, the Dutch Dendrological Association, and the Royal Society for Horticulture and Botany.
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Bergmans also maintained contacts with a number of professional organisations abroad and co-founded the International Dendrology Society (1952).
He collaborated with growers, including Van Empelen and Van Dijk in Aerdenhout, Rozenoord in Amsterdam, Tubbergen in Haarlem, Tottenham and his successor Moerheim in Dedemsvaart, Abbing in Zeist, Turkenburg in Bodegraven, and Faassen-Hekkens in Tegelen. Faassen-Hekkens’ 1934-1935 growers’ catalogue contains an advertisement for the Garden Architecture department, led by none other than John Bergmans.