Urban agriculture plays an important role in many facets of food security, health and sustainability. The city farm is one such manifestation of urban agriculture: it functions as a location centric social hub that supplies food, education, and opportunities for strengthening the diverse sociocultural fabrics of the local community. This paper presents the case of Northey Street City Farm in Brisbane, Australia as an opportunity space for design. The paper identifies four areas that present key challenges and opportunities for HCI design that support social sustainability of the city farm: A preference for face-to-face contact leads to inconsistencies in shared knowledge; a dependence on volunteers and very limited resources necessitates easily accessible interventions; other local urban agricultural activity needing greater visibility; and the vulnerability of the physical location to natural phenomenon, in this instance flooding, present a design challenge and a need to consider disaster management.