Iben Margrete Thomsen has worked with fungi and trees for more than 30 years, both in the context of forests and urban settings. Her main expertise is in tree diseases, such as ash dieback, but she gives advice on a wide range of related topics, from Christmas trees to hazard trees. Protection of large, old trees for the sake of biodiversity as well as their aesthetic value and other ecosystem services is a particular interest of hers, although often fraught with frustration.