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Title: Fall frosts effects on the essential oil of “Native” spearmint in Wyoming

Author
item ZHELJAZKOV, VALTCHO - University Of Wyoming
item Cantrell, Charles
item ASTATKIE, TESS - Nova Scotia Agricultural College
item JELIAZKOVA, EKATERINA - University Of Wyoming

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2012
Publication Date: 11/1/2012
Citation: Zheljazkov, V.D., Cantrell, C.L., Astatkie, T., Jeliazkova, E. 2012. Fall frosts effects on the essential oil of “Native” spearmint in Wyoming. Industrial Crops and Products. 47(11):1603-1606.

Interpretive Summary: “Native” spearmint (Mentha spicata L.) is a widely grown essential oil crop worldwide, and in the Midwest in the United States. There is interest in expanding spearmint production to Wyoming and other states. However, there is no information to determine if spearmints would perform well under the Wyoming short growing season, and if its productivity and oil quality would be affected by fall frosts. The objective of this study was to evaluate the effect of fall frosts naturally occurring at the end of the cropping season on “Native” spearmint productivity and oil profile. Spearmint plants were harvested at the following harvest dates (HD): Sept 14th, Sept 21st, Sept 28th, Oct 5th, Oct 12th, Oct 24th, and Nov 1st. The HD were selected to coincide with the fall frosts in Northern Wyoming. While fresh herbage yields at the Nov 1st HD increased, the oil content at Nov 1st HD was lower than at the Sept 14th HD. Carvone concentration and yield reached maximum at the Oct 12th HD, indicating that “Native” spearmint could be harvested after the first few frosts and provide good oil yields and quality. The early development of spearmints in 2012, along with the demonstrated cold hardiness early in the spring and in late fall may suggest possibility for two consecutive cuts within a single cropping season in Northern Wyoming. This preliminary study suggests “Native” spearmint may be a viable crop for Northern Wyoming.

Technical Abstract: “Native” spearmint (Mentha spicata L.) is a widely grown essential oil crop worldwide, and in the Midwest in the United States. There is interest in expanding spearmint production to Wyoming and other states. However, there is no information to determine if spearmints would perform well under the Wyoming short growing season, and if its productivity and oil quality would be affected by fall frosts. The objective of this study was to evaluate the effect of fall frosts naturally occurring at the end of the cropping season on “Native” spearmint productivity and oil profile. Spearmint plants were harvested at the following harvest dates (HD): Sept 14th, Sept 21st, Sept 28th, Oct 5th, Oct 12th, Oct 24th, and Nov 1st. The HD were selected to coincide with the fall frosts in Northern Wyoming. Indeed, during that time, frost occurred on the following dates: Oct 10th (-1C°), Oct 13th (-2.8 C°), Oct 15th (-2 C°), Oct 19 (-4 C°), Oct 20th (-2.2 C°), Oct 24th ( -1 C°), Oct 25th (-1 C°), Oct 26th (-7) C°, Oct 27th (-5 C°) Oct 28th (-6 C°), Oct 29th (-5 C°), Oct 30th (-6 C°), Oct 31st (-3 C°), and Nov 1st (-3 C°). The first heavy snow occurred from Nov 3-5th. Fresh herbage yields were higher at the Nov 1st HD relative to the Sept 14th HD, while the yields at the other HD were not significantly different. Generally, the oil content was greater at Sept 14, Sept 21st, and Oct 5th HD and lower at the Oct 24th and Nov 1st HD. Carvone concentration (42-75% range) in the oil reached a maximum at the Oct 12th HD. The concentration of limonene was low at the first HD (Sept 14th) and higher in the other HD. The yield of carvone (a function of the fresh herbage yields, oil content, and the concentration of carvone in the oil) was higher at Oct 12th HD, and lower at the other HD. In the spring of 2012, spearmint emerged in late April and was not affected by the Wyoming winter or by the early spring frosts. This preliminary study suggests “Native” spearmint may be a viable crop for Northern Wyoming.