Study on Spearmint and Japanese Cornmint in Mississippi

In previous studies, ‘Native’ spearmint (Mentha spicata L.) and Japanese cornmint (Mentha canadensis L.) have shown potential as essential oil crops for the southeastern United States. Followup field studies were conducted in 2011 and in 2012 at two locations in Mississippi (the North Mississippi Research and Extension Center at Verona, MS, and at Westside Farms, Friars Point, MS), with ‘Native’ spearmint and ‘Arvensis II’ of Japanese cornmint to evaluate the effect of nitrogen rate (150, 200, 250, and 300 lbs/ac.) and location of essential oil yield and composition. The N source was Urea (46–0–0); half of the N for each treatment was applied in early spring and the other half 7 days after the first harvest. Transplanting of mint in the field was done with a wagon wheel transplanter, rows were 38in apart, with the in-row plant spacing of 1 ft. Irrigation was used at both locations: low flow drip tape in Verona and flood irrigation at Friar’s Point to apply approximately 1 inch/acre/week minus the rainfall. Harvesting was done at beginning of flowering, representative samples were weighed immediately and dried at shady place. Dried mint samples (250 g dried material), all in 4 replicates, were steam distilled for extraction of the essential oil. Overall, both mint species grew very well at the two locations. Nitrogen had some effect on oil yields at Friars Point and an effect on the concentration of carvone in ‘Native’ spearmint oil.  ‘Arvensis II’ plants were taller (97 cm) than ‘Native’ spearmint plants (68 cm). Fresh herbage yields at both locations were similar to previous reports from trials conducted in 2007 and in 2008 at Verona with the same cultivars. The dry weight of the plants was greater at Verona (0.8 kg/6 foot of row) compared to Friars Point (0.6 kg/6 foot), and ‘Arvensis II’ provided greater dry weight (0.77 kg) than ‘Native’ spearmint (0.59 kg). Menthol was the main oil constituent of ‘Arvensis II’, whereas carvone was the main oil constituent of ‘Native’ spearmint. The concentration of both constituents was similar to previous reports from Mississippi, from trials conducted with the same species. The concentration of carvone in ‘Native’ spearmint oil was greater at Friars Point compared to the one in Verona. The results suggest ‘Native’ spearmint and ‘Arvensis II’ Japanese cornmint can be viable crops for Mississippi and provide essential oil with desirable composition.