Short rotation wood crops are fast growing trees which can reach harvest size in shorter periods of time than most commercial tree species. While a number of short rotation tree crops can be used for traditional fiber products (e.g., hybrid poplar), their rapid growth and high yields also make them potential candidates for bioenergy and bioproducts uses. A number of tree species are being investigated, but greatest focus in the U.S. has been given to hybrid poplar, shrub willow, and Eucalyptus.