The objectives of this study were to estimate biomass production in commercially grown short rotation coppice willow in Denmark and to investigate effects of site and management factors on willow yield. Biomass production assessed by non-destructive sampling on 296 plots from 25 plantations was analyzed using a mixed model approach. Average production in the stands varied between 2.4 and 15.1 odt ha⁻¹ year⁻¹, and average second rotation growth (8.2 odt ha⁻¹ year⁻¹) was significantly higher than first rotation growth (6.5 odt ha⁻¹ year⁻¹). Annual production was significantly correlated with clone, soil texture, soil drainage, fertilization, weeds, rotation number, and shoot age. Further, interactions between clone and soil drainage as well as between clone and soil texture were significant, indicating the importance of a site-specific choice of clones.