Green activism and guerrilla gardening lie at the more informal end of the urban food growing movement, but little is known about the extent of this practice or the future of such unplanned activities. Accordingly, this paper firstly explores a range of informal Urban Agriculture practices, illuminating the practice within Europe, North America, Africa and other continents. The paper then proceeds to focus explicitly on Salford, UK, where guerrilla gardening is being encouraged by the local authority. Using ethnographic and interview data, we focus on the actors involved, their relationship with authority and the wider impact of their activities; exploring their motives, aspirations, values and beliefs. The results reveal the ability of the informal movement to regenerate ‘forgotten’ space and bring communities together, and the ‘darker’ side of the activity, with actors sometimes restricting access to colonised land. Ultimately, the paper reveals how this movement is expanding and that more research is required to better understand the actions of those who pursue a more informal approach to urban gardening and those who seek to regulate land use activity.