Grassroots initiatives for sustainable development are blossoming, offering localised alternatives for a range of societal functions including food and energy. Research into grassroots organisations often recognises the difficulties grassroots groups face to continue operations. However, there is a need for better understanding dynamics that enable or constrain grassroots organisational survival. Here, we specifically shed light on how such survival is dependent on the organisation's ability to construct legitimacy. In the context of community supported agriculture (CSA), we explore different legitimacy types and strategies. We learned that CSAs predominantly work to garner legitimacy from their members and that survival seems associated with social capital building. In addition, we observed a moralisation of food provision that describes why new and possibly inconvenient terms of exchange still amass legitimacy. As external audiences remain at a distance, they often misunderstand CSA, their deliverables and impacts on social welfare.