The genus Miscanthus contains species which have high biomass potential. Phenotypic variation in traits relevant to yield and quality has been evaluated in a replicated spaced plant trial containing 249 genotypes. Results in the third year following establishment show large variation in canopy height, stem density, flowering time, leaf senescence rate and biomass yield. This variation in phenotypic traits has been used to inform breeding decisions for the generation of new, improved genotypes suited to different environments and end uses. Several lines were found to exceed the spaced plant yield of M. x giganteus. We expect that new high yielding hybrids, optimised for a wide range of current and predicted environmental conditions, will make a substantial contribution to fossil fuel substitution in the future.