Households and community organizations are involved in the creation, use, care, and management of urban spaces, including through food practices such as planting, foraging, harvesting, weeding and pruning at the ambiguous edges of public and private property. Drawing on case studies in Boston, Massachusetts, we examine how commons are articulated through these practices, particularly in relation to multiple dimensions of property rights. Specifically, we ask how food practices can open urban spaces to negotiations around access, responsibility, care, and ownership, especially when (property) ownership is not an end-goal, but a circumstance shaping other practices. Using interviews and participant observation of individuals and organizations involved in urban food provisioning, we explore how households and community organizations are interrupting fixed notions of property ownership, by practicing urban commons. These practices and negotiations demonstrate ongoing shifts in the meanings of urban space with flexible understandings of property and ownership.