Ethnographic research on plant species used in ritual festivals of the Nung people in the northern mountainous region of Vietnam

In traditional agrarian societies, plants not only play a material role but are also deeply embedded in ritual life and the spiritual world of communities. The Nung people in the northern mountainous region of Vietnam are a long-established community whose livelihoods are closely linked to mountain–forest ecosystems, in which ritual festivals occupy a central position in maintaining spiritual order and social relations. Although Nung ritual festivals have been studied from various perspectives, the use of plants in these practices has not yet been systematically examined from the perspective of ritual ethnobotany. This study aims to clarify the roles and meanings of plants in traditional Nung ritual festivals, thereby contributing to filling an existing research gap. The study employed an ethnographic approach combined with ethnobotany and was conducted in Son Hong village (Lang Son, Vietnam) in 2025. Data were collected through participant observation and semi-structured interviews with 54 Nung informants who have long resided in the study area. The Frequency of Citation (FC) and Relative Frequency of Citation (RFC) indices were used to assess the prevalence and relative importance of plant species within the ritual festival system. The study documented 23 plant species used in six major ritual festivals of the Nung. These species originate from diverse sources, including natural environments, home gardens, and markets, and serve religious, ritual offering preparation, and decorative functions. FC and RFC analyses reveal a clearly stratified structure of ritual plant use, with a small number of core species playing central roles and many others serving supportive and context-dependent functions. The use of plants in ritual festivals reflects the traditional ecological knowledge and worldview of the Nung, in which plants act as symbolic mediators connecting humans, ancestors, and the natural environment. The findings suggest a cultural practice–based approach to conservation, emphasizing the role of rituals and indigenous knowledge in biodiversity conservation and sustainable development.