Development of the garden, under co-ordinator Annie Beattie, started a year ago and now involves an average of 10 volunteers a week.
The garden is above Chelmer St just south of the Oamaru Public Gardens, and the group uses resources from the Waitaki Resource Recovery Park across the road.
The aim is to teach people gardening skills, and the initiative has attracted growing community support in the form of volunteers and financial assistance.
The celebrations included a composting demonstration, planting of native plants and shrubs and making "bird puddings" from lard, wheatgerm, breadcrumbs and ground linseed to feed the birds attracted to the garden.