Why has maize, a plant with origins in the New World, become ritually important in an indigenous Southeast Asian religion? While environmental conditions and agricultural economics are key determinants of everyday resource management practices in insular Southeast Asia, it is necessary to consider ethnic identity, political economy, and social structure in order to understand the religious significance of natural resources in contemporary society. Linguistic, cosmological, and horticultural data are combined with an analysis of local perceptions of culture and environment. This information is used to explain the transformation of an introduced plant into an indigenous sacrament. Ethnographic data, including a brief case study of the role of maize in marapu ‘ancestor worship’ and the cultural history of the Kodi people who live on the Indonesian island of Sumba, are the basis for a discussion of agrarian change and social history in Kodi. The data are also used to explore the possibility of using information about contemporary Sumbanese society to gain a better understanding of historical processes in eastern Indonesia.