Commons approaches in the seed sector are multi-faceted: They span from traditional seed systems, i.e. seed sharing networks, to recent anti-enclosure movements that resist intellectual property rights on varieties, like organic breeding initiatives. This paper derives a conceptualization of ‘Seed Commons’ at the local and regional level, based on a comprehensive transdisciplinary research process that integrates diverse types of knowledge, both from practitioners (German and Philippine seed initiatives, companies and NGOs), and the scientific community. As a result, we identify four core criteria that characterize diverse Seed Commons arrangements at local and regional scales: (1) collective responsibility, (2) protection from private enclosure, (3) collective, polycentric management, and (4) sharing of formal and practical knowledge. Discussing these Seed Commons criteria in the context of different Commons approaches, we find that Seed Commons transcend the distinction between traditional (natural resource) Commons and New Commons approaches, by integrating biophysical, informational and cultural elements in their collective governance. Reaching beyond resource characteristics, the Seed Commons criteria reflect practices of Commoning, which aim to fulfill social functions such as farmer empowerment and food sovereignty.