He has a degree from Frederiksoord Horticultural College and further education from ‘Muskauer Schule’, Bad Muskau, Germany. He has been working at Paleis Het Loo from 1983 – at first as a Deputy Head Gardener, the Head Gardener and now a Gardens Consultant.

He has also been involved in the National Cultural Heritage Agency , participating in the project ‘Dutch gardens in Russia’ focus on the Summer Garden in St Petersburg, and the Peter and Paul park in Jaroslavl, from 2008-2019. In addition, collegial contacts and consultancy  at Hampton Court Gardens, The Danish Palace and Properties Board, (Frederiksborg and Fredensborg Palace) and Drottningholm Palace. He has also experience as a:
– Member of the ‘Arbeitskreis Deutscher Orangerieën’

– Board member of ‘Cascade’, the Dutch garden History Society

– Board member of the Dutch head gardeners Guild from 2008 – where he is still a member.

Willem Zieleman will give a presentation about the box hedges at Het Loo on the Hedges-webinar, with the title: «In search of a hedge». He is also contributing on the Management of Orangery plants-webinar and to the webinar on Ponds and Fountains. Willem is also one of the tutors/mentors on the «Ponds and fountains in Historic Gardens» workshop at Het Loo in June 2024.