New forms of urban gardening are gaining momentum in cities, transforming the conventional use and functions of open, green and public space. They often take place through informal and temporary (re)use of vacant land, as part of greening strategies or social inclusion policy through new modes of land use management, green space governance and collaborative practices. Particular emphasis is placed on shifted meanings of the notion of open public space by referring to its openness to a diversity of uses and users that claim it and relates to the questions of access rights, power relations among actors, negotiations and the so-called right to use and re-appropriate land. By using examples drawn from the Greek and Swiss cases, this chapter underlines differences and similarities in urban gardening practices, social and institutional contexts, collaborative governance patterns, motivations, levels of institutionalisation, openness and inclusiveness of space. More specifically it calls attention to the critical role of the temporary nature of these initiatives in relation to their multifunctional, spatial and socio-political aspects that affect new configurations of urban green areas and public space as well as related planning practices.