Mainstream urban planning relies on economic growth to produce social and environmental benefits, but in low-growth areas that relationship is not functional. We argue that urban planning in low-growth areas could reveal new ways to produce welfare by taking action without pre-defining the outcomes. We define such planning as co-evolutionary, and study how urban planners in the City of Turku, Finland, applied it in three low-growth contexts. We conclude that the approach was recognized, but taking action under conditions of uncertainty was challenging. Further, we identify three activities and challenges related to coevolutionary urban planning in low-growth areas.