Background <p>The southeastern<!--Query ID="Q1" Text="As per standard instruction, city is required for affiliations; however, this information is missing in affiliation [6]. Please check if the provided city is correct and amend if necessary." Resolved="yes"--> United States holds immense potential for producing cellulosic feedstocks to support the emerging biofuel industry. However, the development of a viable cellulosic biofuel sector depends on consistent, site-specific, and seasonally available biomass supply. Biomass sorghum has emerged as a promising annual feedstock, but understanding its growth dynamics and environmental sensitivities is essential for optimizing yield and supply logistics.</p> Methods <p>A four-year, multi-location<!--Query ID="Q2" Text="Please confirm if the author names are presented accurately." Resolved="yes"--> study was conducted across six sites in the southeastern US to assess the influence of genotype, environment, and management on biomass sorghum growth and productivity. The objectives were to: (1) quantify the growth and biomass dynamics of biomass sorghum under different environments in the Southeast US and 2) estimate early harvest yield penalties based on its seasonal biomass growth patterns.</p> Results <p>Stalk density and <!--Query ID="Q3" Text="Please check if affiliations were captured and presented correctly. Otherwise, kindly amend if necessary." Resolved="yes"-->plant height varied significantly across sites, years, and genotypes, reflecting strong genotype × environment interactions. Biomass accumulation followed a sigmoid growth pattern, with differences in heat unit requirements and the number of days to reach maximum biomass yield. Northern sites exhibited faster biomass accumulation but shorter growing seasons and higher early harvest penalties of up to 25%. End-of-season biomass ranged from 9.3 to 21.7 Mg ha⁻¹, with site accounting for the greatest source of variation, followed by site × year interaction.</p> Conclusions <p>This study reveals<!--Query ID="Q4" Text="Please check if the article title was captured and presented correctly. Otherwise, kindly amend if necessary." Resolved="yes"--> strong spatiotemporal variability in biomass sorghum growth and yield across environments. The results emphasize the need for site-specific genotype selection, management strategies, and harvest scheduling to minimize yield losses and enhance feedstock reliability. These insights contribute to optimizing biomass sorghum production and strengthening sustainable bioenergy systems in the southeastern US.</p> Graphical Abstract <p>Seasonal growth, early harvest <!--Query ID="Q5" Text="Please check if the Graphical abstract was captured and presented correctly. Otherwise, kindly amend if necessary." Resolved="yes"-->penalties, and end-of-season yield of biomass sorghum in the southeastern US</p> <p></p>