No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. S cotch and Native spearmint are grown as essential oil crops in many parts of the world (Bienvenu et al., 1999;Lawrence, 2006). Both Scotch and Native spearmints have been used in the production of essential oils, teas, and to fl avor foods, prepared dishes, and drinks. Spearmint essential oils are used in the food and pharmaceutical industries and are found in various consumer products including chewing gum, toothpaste, mouthwashes, as well as in pharmaceuticals, confectionary, and aromatherapy (Mint Industry Research Council, 2009). Both whole essential oils and individual essential oil constituents such as (-)-carvone have antimicrobial properties (Aggarwal et al., 2002;de Carvalho and Da Fonseca, 2006;Chao et al., 2000;Kanatt et al., 2008;Rafi i and Shahverdi, 2007;Rasooli et al., 2009;Sivropoulou et al., 1995;Sokovic et al., 2009).Th e midwestern and northwestern United States are considered ideal for spearmint production (USDA-NASS, 2009). In 2008, the United States produced 1.09 million kg of spearmint oil, and the average essential oil yields for the same year were 132 kg/ha (USDA-NASS, 2009). With increased ethanol production from corn (Zea mays L.), some U.S. spearmint farms have recently switched to growing corn to meet the demands of ethanol production. According to the MIRC, there remains a current market for spearmint oil in the United States (R. Lundy, the MIRC, personal communication, 2008). Th e continued market for spearmint oil in the United States off ers an opportunity for growers in the Southeast to capitalize on the spearmint essential oil market. However, spearmint production practices in the Southeast have not been scientifi cally assessed. In this study, we evaluated the eff ects of N application rate and cut (harvest time) on Scotch and Native spearmint herbage yields, essential oil content, oil composition, and major oil constituent yield [(-)-carvone, (R)-(+)-limonene, and eucalyptol] on a per area basis.
MATERIALS AND METHODS
Field ExperimentsWhile spearmint seed is available for home gardeners, the two species are natural hybrids (Tucker and Fairbrothers, 1990;Tucker, 1992) and their subsequent progeny may produce plants with diff erent phenotypes or chemical composition. Th erefore, commercial spearmint cultivars for essential oil production in the United States and abroad are propagated only vegetatively (Ellis and Stevenson, 1950;Lawrence, 2006;Tucker and Fairbrothers, 1990;Yankuloff et al., 1996). To minimize pest and disease pressure in our studies, we obtained certifi ed virus-free planting material of Scotch and Native spearmints from the Summit Plant Laboratories, Inc. (Fort Collins, CO). Spearmint plants from each cultivar were equal in size, (approximately 10 cm high), and each had several pairs of leaves. Th e spearmint plant...
