Local perceptions of the benefits versus negative impacts of weedy grasses in central Madagascar, with a focus on the genus Digitaria

Plants and agricultural practices are an integral part of human food systems and well‐being. Here, an example of an ethnobotanical research approach is provided to increase our understanding of the relationship between plants and human activities in Madagascar, where the agricultural sector is the local economy basis. This research examines weeds of the Poaceae family, assessing their recognition and societal impacts, and quantifying farmers' perception of the Poaceae weed's status in cropping systems. A better understanding of farmers' weed knowledge will strengthen our ability to inclusively support rural highland Malagasy food systems, incorporating science with traditional knowledge. Research on the perceptions and knowledge of Poaceae weeds was conducted in three areas of Madagascar's central highlands: Itremo massif, Ambohidray village and Vakinankaratra region. This work aims to identify the best‐known species and understand their roles in crop and livestock systems. Additionally, it presents detailed data on Digitaria species. The approach was based on field surveys and farmer's interviews, with plant voucher specimens and photographs to facilitate identification. Relative frequency of citations, confidence interval, and use values indexes were calculated to assess cultural significance. We carried out 111 interviews, where 87 taxa were mentioned, of which 51 are Poaceae, including 11 Digitaria species. Farmers classify the Poaceae weeds in three ways: their impacts on agricultural activities, use category and vegetative growth patterns, the latter especially significant for Digitaria. Locally common grasses are perceived as weeds when they are abundant and cause yield loss. The most damaging species is Digitaria humbertii, confirmed by half of the interviews. More than 40% of the farmers use Poaceae weeds in composting, more than 20% as fodder, and more than 8% as medicine. Overall, 67% of the species mentioned are judged useful. The diversity of useful species and the associated indigenous knowledge is important to the local communities, but, weeds are still perceived as negative generally. The Poaceae are overall neglected in Malagasy ethnobotany, and an in‐depth analysis of farmer knowledge is needed. The data obtained will be useful for future studies and the conservation of agrobiodiversity, especially endemic species that are not widely known.