In the U.S., much of the effort to develop new bioenergy and bioproduct crops has focused on herbaceous grasses and short rotation woody crops that can be used as cellulose sources. Almost any grass can be used as a cellulose feedstock, but current efforts center on developing grasses that can be produced with high yields on large acreages, using commercial agricultural production systems. Many of the species of interest are currently grown as forage crops for livestock. However, the varieties and management practices best suited for forage production are not necessarily those most appropriate for bioenergy and bioproduct uses. Therefore, new varieties and production systems need to be developed. The herbaceous grass receiving the greatest attention in the U.S. is switchgrass (Panicum virgatum). The major focus of the Europeans has been on Miscanthus, and this crop is creating interest in the U.S. as well. A number of other grass crops could also be used for bioenergy and bioproducts, but research is limited. Among those most commonly mentioned as potential candidates are Arundo donax and reed canary grass. Additional limited efforts are underway to develop mixed grass stands (stands consisting of more than one species of grass).