Effects of Planting Time and Quality Characters of Essential Oil in Peppermint

Evaluation for essential oil composition and to assess the change in quality of essential oil with age, harvesting time and maturation phase M. piperita clones namely MP-1 to MP12 were taken under study. It was found that nine cultivars with basic chromosome number 2n=72, were best suited under fluctuating environments with respect to oil content and quality as well with more than 70% menthol content. Oil yield peaked at 114 kg ha-! on 31 January. At this time the composition of extracted oil was: menthol 43.1, menthone 28, menthyl acetate 6.6, cineole 4.1, and menthofuran 3.8%. After this date oil yield declined steadily because of leaf senescence, while the percentage of menthol, menthyl acetate, and menthofuran increased, and menthone decreased.