This paper presents an agent-based model that explores the conditions for ongoing participation in community gardening projects. We test the effects of Ostrom’s well-known Design Principles for collective action and use an extensive database collected in 123 cases in Germany and two case studies in the Netherlands to validate it. The model uses the Institutional Analysis and Development (IAD) framework and integrates decision mechanisms derived from the Theory of Reasoned Action (TRA). This allows the analysis of volunteer participation in urban community gardens over time, based on the garden’s institutions (Design Principles) and the volunteer’s intention to join gardening. This intention is influenced by the volunteer’s expectations and past experiences in the garden (TRA). We find that not all Design Principles lead to higher levels of participation but rather, participation depends on specific combinations of the Design Principles. We highlight the need to update the assumption about sanctioning in such systems: sanctioning is not always beneficial, and may be counter-productive in certain contexts.

In order to better understand the mechanisms leading to resilient urban gardening systems, we revisit Ostrom’s institutional design principles with an agent-based model (ABM) and implement behavioural dynamics as structured by the theory of reasoned action. Our experiments show that sanctioning bad behaviour in general increases the group cohesion and leads to longer collective action. Higher success rates occur for cases in which volunteers join for socialising rather than just taking crop yield. However, the design principles are not blueprints leading de facto to robust gardening systems: the combination of these principles is instead determining.