Peppermint (Mentha ×piperita) is currently not a common crop in the southeastern United States. Recently, there has been an interest in peppermint as an essential oil crop for this region. In 2007, a field experiment was conducted in Mississippi to determine the effect of nitrogen (N) (0 and 80 kg·ha−1), location (Verona and Stoneville), and harvesting stage (bud formation and flowering) on peppermint productivity, oil content, and composition. Peppermint biomass yields were higher at Verona (8.12 t·ha−1) than at Stoneville (6.12 t·ha−1). However, the essential oil content was higher at Stoneville (1.1%) than at Verona (0.6%). Generally, N rate at 80 kg·ha−1 did not affect oil yield and composition compared with 0 kg·ha−1. The concentrations of the major essential oil constituents were: (-)-menthol at 26% to 30%, (-)-menthone at 14% to 21%, (+)-menthofuran at 5% to 11%, and eucalyptol at 3% to 4% of total essential oil (wt/wt) and were generally within the values previously reported. The concentrations of (-)-menthone and (+)-menthofuran were significantly higher at Stoneville, 21% and 11%, respectively, than at Verona (14% and 6%). The (-)-menthol, (-)-menthone, and (+)-menthofuran yields/ha were higher at Stoneville than at Verona. Overall oil content and yields were higher at bud formation than at flowering, 1.3 and 1.8 times, respectively. In addition, the concentration of (-)-menthone and eucalyptol and the yields of (-)-menthone, (+)-menthofuran, and eucalyptol were higher at bud formation than at flowering. The results from this study demonstrated peppermint can be successfully grown in Mississippi and provide essential oil yields and composition comparable to those in the northwestern United States, the traditional peppermint-growing region.

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Two pot experiments were conducted to evaluate noncomposted hair byproduct as a nutrient source for container-grown crops. Lettuce (Lactuca sativa ‘Green Leaves’) and wormwood (Artemisia annua ‘Artemis’) were grown in a commercial growth substrate amended with 0%, 2.5%, 5%, or 10% by weight hair waste or controlled-release fertilizer (CRF) or were watered with a complete water-soluble fertilizer (WSF). After harvest, yellow poppy (Glaucium flavum) was grown in the pots and substrate that previously grew wormwood, and feverfew (Tanacetum parthenium) was grown in the pots and substrate previously containing lettuce. The 5% hair treatment and the commercial fertilizer rates were calculated to provide the same amount of nitrogen (N) during production of lettuce and wormwood based on 50% N availability from hair. Yields in treatments containing hair or CRF or watered with WSF were higher than in the untreated control. The highest lettuce and wormwood yields occurred with CRF followed by WSF and 5% and 10% hair treatments. However, yield of yellow poppy was higher in the hair treatments than yields in inorganic fertilizer treatments or in the untreated control. Feverfew yields did not differ among fertility treatments, but yields in fertility treatments were higher than those of control. Lettuce leaf moisture content was lower, but soluble solids were higher in plants in the hair waste treatments than in the WSF or CRF treatments. Total phenolics in lettuce did not differ among treatments. Total aerobic and coliforms plate counts were similar for all samples, averaging 6.0 and 1.2 log cfu/g, respectively. Results from this study suggest that noncomposted hair waste could be used as a nutrient source for container-grown plants. Hair waste should not be used as a single nutrient source for fast-growing plants because of the time needed for degradation of the hair before release of plant nutrients.

Steam distillation of essential oil crops produces residual distillation wastewater that is released into the environment. This study evaluated the effects of three plant hormones [methyl jasmonate (MJ); gibberellic acid (GA3); and salicylic acid (SA)] at three concentrations and the residual distillation water from 15 plant species applied as foliar spray on biomass yields, essential oil content, and essential oil yield of Mentha ×piperita ‘Black Mitcham’ and Mentha spicata ‘Native’. Overall, the application of SA at 1000 mg·L−1 increased biomass yields of both species. More treatments influenced essential oil content in ‘Black Mitcham’ peppermint than in ‘Native’ spearmint. Application of MJ at 100 and 1000 mg·L−1, GA3 at 10 mg·L−1, SA at 10 or 100 mg·L−1, and distillation water of Achillea millefolium, Ammi majus, Artemisia absinthium, Cymbopogon flexuosus, Cymbopogon martinii, Chrysanthemum balsamita, and Hypericum perforatum increased the essential oil content of peppermint, whereas the oil content of spearmint was increased only by application of Monarda fistulosa distillation water. Application of MJ at 100 mg·L−1, SA at 100 mg·L−1, and A. absinthium, C. flexuosus, and C. balsamita distillation waters increased essential oil yields of peppermint, whereas the application of SA at 1000 mg·L−1 and distillation water of A. absinthium, Lavandula vera, and M. fistulosa increased oil yields of spearmint. This study demonstrated that the residual distillation water of some aromatic plant species may be used as a tool for increasing essential oil content or essential oil yields of peppermint and spearmint crops.

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