Human ecological relations with plants are fundamental to the food sovereignty of indigenous and rural communities. Our study focused on subsistence farming communities in the mountainous Debark District of northern Ethiopia, to learn how their relations with plants contribute to self-determination of the food system. First, to understand how farmers perceive plant diversity, we conducted a linguistic analysis of local plant names, as well as pile-sorting activities. We found that farmers perceive greater diversity among plants central to their livelihoods, mainly domesticated crops. Second, we analyzed the roles of plants within the food system, including consumption of plants as food, use of plants for food system activities, conservation of plants that enhance agroecosystem functionality, and the suppression of plants with negative impacts. Third, we examined farmers' knowledge of plant phenology and the timing of agricultural activities in the context of climate change. Because farmers reported increasing variability in the timing of the rainy season, we conducted a quantitative analysis to identify non-domesticated plants that could be used as seasonal cues for planting and harvesting. Fourth, to assess the spatial availability of useful plants, we conducted participatory mapping, vegetation survey, and analysis of remote-sensed imagery. While participatory mapping affirmed the significance of indigenous trees to farmers, vegetation survey and analysis of satellite images indicate that such trees are exceedingly rare, as woody vegetation is increasingly dominated by Eucalyptus globulus, an introduced species promoted for its multifunctionality and high market value. Fifth, we spoke with local clergy about the conservation of plants around Ethiopian Orthodox churches. We confirmed that church forests are critical habitat for rare indigenous trees and shrubs. However, most species are planted and tended by church communities, challenging the view that these forests are remnants of a pre-agricultural ecosystem. Rather, Ethiopian church forests provide an instructive example of community conservation based on the value of sacred space. In conclusion, we offer practical recommendations for local government and civil society institutions, as well as suggestions for future research to enhance the food sovereignty of Debark and other subsistence farming communities.