Interannual climatic variability and essential oil dynamics in Mentha piperita cv. Kristinka: Insights from a 13-year field evaluation

Long-term evaluations of climatic influences on essential oil (EO) yield and composition remain limited for cultivated peppermint. This study investigated the impact of air temperature and precipitation on EO yield and major constituents of Mentha piperita cv. Kristinka over a period of 13 years (2010–2022), in Slovakia. Essential oils were obtained by hydrodistillation and analyzed by GC/MS. The average EO yield was 2.4%, it ranged from 0.8% to 4.0%. Menthol was the dominant component (69.9%), followed by menthone (12.7%) and limonene (3.4%). Interannual climatic variability was substantial, with mean annual temperature ranging from 7.7 to 10.2°C and annual precipitation from 454.5 to 887.1 mm. Pearson correlation analysis revealed mostly weak and statistically nonsignificant associations between annual climatic variables and EO parameters. A moderate positive correlation was observed between July temperature and EO yield, while precipitation showed limited influence. Polynomial regression models did not provide predictive value. Principal component analysis explained 70.98% of total variability and revealed year-specific clustering patterns associated with EO yield and menthol content. Overall, annual climatic averages were insufficient predictors of EO variability, suggesting that intra-annual climatic dynamics and additional environmental or physiological factors play a more substantial role in regulating secondary metabolite production.