Research on crop distribution offers critical insights into the development of agricultural civilisations and the globalisation of food. Fagopyrum esculentum(common buckwheat) and F. tataricum (Tartary buckwheat), both of which originated in China, are important food and famine relief crops. However, the history of their cultivation and spread has remained unclear because of a lack of reliable species-level identification standards for Fagopyrum macrofossils. To address this issue, we first established morphological identification criteria for F. esculentum and F. tataricum grains through charring experiments and systematic observation of modern buckwheat grains. These standards were then applied to the identification of macrofossils from the Xueshan site in southwestern China and the Dasikong and Beitaishang sites in east-central China, which are crucial for understanding the origin and dispersal of buckwheat. Species-level identification confirmed the presence of F. esculentum at these sites during the Tang, Song and Yuan Dynasties (618–1368 ce). A synthesis of macrofossil finds and historical records revealed that the 7th to 13 century were the periods during which F. esculentum spread across China. During the Tang and Song periods (618–1279 ce), common buckwheat spread eastwards to the middle and lower reaches of the Yellow River in east-central China. By the Liao and Jin periods (907–1234 ce), its cultivation range had expanded into northeastern China. This study shows that the increasing demand for famine relief food, the widespread adoption of flour milling techniques and the favourable growth characteristics of buckwheat all facilitated its extensive cultivation and integration into agricultural systems in northern China.
