Mentha canadensis L., a subtropical plant, can withstand first few fall frosts when grown in northern climate

Japanese cornmint (Mentha canadensis L.) is a subtropical essential oil crop grown in Asia and South America. The essential oil of Japanese cornmint is the only commercial source for production of natural crystaline menthol, an important aromatic agent used in various industrial applications. The United States is a major importer and consumer of menthol and de-mentholized oil. Currently, there is no commercial production of Japanese cornmint in the United States. The objective of this study was to evaluate the effect of harvest dates (HD) in the fall (designed to cover the period of fall frosts) on essential oil content, oil composition, and the yields of individual oil constituents of two Japanese cornmint cultivars, 'Arvensis 2' and 'Arvensis 3'. Field experiments were conducted in northern Wyoming (44°45.686′ N and −106°55.479′ W, at elevation of 1171 m asl). From the first to the last HD, there were 16 frosts in 2011 and 27 frosts in 2012. Results showed that Japanese cornmint can withstand the first few fall frosts and provide good yields with desirable oil composition. The fresh yields of the two cultivars were not different for all of the HD in 2011 and for some of the HD in 2012. However, in 2012, 'Arvensis 3' provided larger fresh herbage yields than 'Arvensis 2' on 5 October, 19 October, 26 October, and 2 November HD. Oil content in fresh herbage varied from 0.126% to 0.571%, and oil yields varied from 18 to 152 kg/ha as a function of HD and cultivar. Menthol concentration in the oil varied from 67% to 85% depending on HD, and was not significantly different between the two cultivars at any given HD. Later HD (5-19 October), after the first few fall frosts, did not decrease menthol concentration in the oil of Japanese mint cultivars. Japanese cornmint could be a viable crop and potentially a biofuel feedstock for northern latitude (around 44° N), at elevation of around 1170 m asl.