Bioenergy crops help reduce America?s reliance on fossil fuels, and mitigate global warming. Miscanthus �giganteus (Mxg) is a promising bioenergy crop because it produces high yields, needs few inputs, and grows well during the cool weather of early spring and late fall when few other warm-season grasses can. However, only a single, sterile vegetatively propagated cultivar of Mxg is currently available in the U.S. Such a reliance on only one cultivar is risky, because the emergence of a virulent disease or pest could damage or kill all plantings. Additionally, it should be possible to breed new Mxg cultivars that have even higher yields and are better adapted to U.S. environments than the current cultivar. Mxg is an interspecific hybrid of the parental species M. sacchariflorus (Msa) and M. sinensis (Msi). Msa is naturally found from central China to eastern Russia, in Korea, and in Japan. Msa includes the tallest and most cold-hardy populations of all Miscanthus, but little had been known about genetic diversity of this species. We collected more than 600 individuals of Msa from throughout its natural range. Using thousands of molecular markers, we identified six distinct genetic groups of Msa, three of which were tetraploid (N China/Korea/Russia, S Japan, and N Japan) and three of which were diploid (Yangtze, N China, and Korea/NE China/Russia). Field trials were conducted at six locations to evaluate yield-potential and adaptation. Some accessions were observed to have exceptional height, yield potential and tolerance to chilling temperatures. These data and accessions of Msa will be useful for breeding improved cultivars of Miscanthus for biomass production. This study resulted in the publication of ten papers in peer-reviewed scientific journals.