Miscanthus sinensis is a perennial C4 grass that is one parent of the economically important hybrid biomass species, M. ×giganteus. Clark et al. evaluate 620 M. sinensis accessions from most of its native range with >20 000 nuclear and plastid markers, and identify six genetic groups. They find that coastal south-east China was a refugium of M. sinensis during the last glacial maximum, and that the species recolonized Japan prior to recolonizing similar latitudes in mainland Asia. Ornamental cultivars originate almost exclusively from southern Japan, and many marketed as M. sinensis have hybrid ancestry from M. sacchariflorus.