Mennega studied biology at Utrecht University, receiving his degree in 1947.
He was then hired as a taxonomist at the Utrecht University Botanic Gardens.
[1] In 1988, Frans Stafleu and Richard Sumner Cowan published the second edition of Taxonomic Literature: A Selective Guide to Botanical Publications and Collections, with Dates, Commentaries, and Types.
[1] After Cowan left the project, Stafleu began collaborating with Mennega on a supplement series.
[2] Mennega took over the majority of writing and compiling after 1995 due to the decline of Stafleu's health.