The 1^st Horizon Scanning workshop of UB3Guard gathered 30 members from 13 countries to discuss the current state of urban tree biosecurity and to analyse the emerging and future tools and strategies that may help us to better protect the trees in urban settings. The meeting was held in COST premises at Avenue du Boulevard - Bolwerklaan 21 which offered not only excellent meeting facilities but also a breathtaking view over the city of Brussels. An excursion and talk with stakeholders who work with city tree management completed the meeting, and we left Brussels with new insights and an increasing feeling that we are working with something extremely important.