To mitigate supply risks associated with Hevea brasiliensis, Taraxacum kok-saghyz is being developed as a promising temperate source of natural rubber. For it to be successfully integrated into conventional cropping systems, optimized agronomic practices are required. The present study investigates the effects of sowing season (spring vs. autumn) and harvest timing (June–October) on rubber yield, determined by root dry weight and rubber content. Field trials were conducted at two contrasting locations in Germany using wild-type T. kok-saghyz and the interspecific hybrid ‘Hyb207’. Root dry weight accumulation was influenced by genotype, sowing season, harvest date and site conditions. Despite this variability, autumn sowing increased modeled root dry weight by approximately 81% and rubber content by 84% on average compared to spring sowing. In addition, autumn-sown plants reached peak root dry weight earlier in the season than their spring-sown counterparts. These results demonstrate that strategic selection of sowing and harvest windows is critical for optimizing yield formation. Site-specific management strategies can enhance biomass production and facilitate the integration of Tks into temperate cropping systems.