In the summer of 2011 local media reported that in Cologne a “green smartmob” of more than 170 people had gathered on a vacant plot south of the city centre. 1 Sneaking through the fence and embellishing the brownfield site with marigolds, sunflowers, pumpkins, and palm trees, they staked their claims to more political involvement of local residents in the future of this site, which had lain barren for years. This unauthorized greening of an urban brownfield site sounds like a typical act of “guerilla gardening” – rebellious, subversive and immanently political.