Urban agriculture has become a rapidly growing international movement. Most urban gardens are established, organized and managed collectively as commons. When applying collective action theory to urban gardens, it becomes evident that they are special in the motivation why people get organized to produce food. Particularly in developed countries, urban gardens emerge in response to a lack of participation in city development, democratic use of public spaces or opportunities and time for socializing instead of economic competitiveness or the desire for regional food. Therefore communities emerge which design, change and manage their urban landscape and rise up new urban social-ecological systems. Yet, urban agriculture, or urban gardens, lack closer scientific examination in this respect. Therefore, the paper presents elements which are characteristic to describe this recent development. Likewise, we present criteria to explore the differences between the gardens. With three pilot case studies we demonstrate the applicability of these criteria in urban gardens to differentiate between different degrees of collectively used resources and therefore diverse levels of collective action in urban garden projects. We can show that many urban agriculture movements offer the possibility to build new regional identities through the option of sharing time, sharing knowledge and participation in public decisions.