In recent years, miscanthus has emerged as a very promising alternative energy crop predominantly due to its low input requirements and high dry matter yield potential. In this study, inter-annual variation in biomass yield and composition between 2004 and 2010 was studied in a multi-genotype trial planted in south Germany. The main factors of interest in the inter-annual variation were climatic conditions (rainfall and temperature) and different harvest dates (January/February/March/April). The multivariate regression analysis showed that the interactions of harvest date-aging and harvest date-rainfall have significant effects on the stability of biomass quality characteristics over the productive growth period. In M. sacchariflorus the harvest date-aging interaction improved the combustion quality by reducing the Mg concentration by 29% and ash by 18%, whereas the harvest date-rainfall interaction contributed by decreasing the concentrations of Ca, Si and N by 8%, 4% and 6%, respectively. The M. x giganteus genotypes showed more consistency in mineral concentrations, especially K and Cl, and dry matter yield in comparison to M. sinensis over the productive growth period. (C) 2014 Elsevier B.V. All rights reserved.