Observatree aimed to develop a GB-wide Tree Health Early Warning System to enable early detection of tree pests and diseases, thereby supporting efforts to protect woodlands and forests. This was achieved by building capacity amongst a cohort of trained volunteers to carry out surveys for tree pests and diseases, and to assist with processing and verifying tree health incident reports. This publication reports the results of interviews conducted with professionals and volunteers participating in Observatree in order to learn from their experiences. This evaluation study investigated a number of aspects of the experiences of participants, including: their motivations, positive experiences, received and potential benefits, not so positive aspects of their experiences, and suggestions for improvements