Introduction Optimizing fertilization strategies in Melissa officinalis L. requires an integrated assessment of biomass production and secondary metabolite synthesis. Methods This study evaluated the effects of organic and organomineral fertilization on herbage yield, essential oil (EO) yield, and leaf rosmarinic acid (RA) content under field conditions in Ödemiş (Türkiye) during the warm and dry 2024 growing season. A split-plot design was used, with two cultivars (Melis and Quedlinburger) assi