Mentha × cardiaca J. Gerard ex Baker - syn. Mentha ×gracilis Sole; Mentha × gentilis auct. (f.cardiaca) - Lamiaceae
Scotch mint, Scotch spearmint, Scottish mint, Scottish spearmint, ginger mint, red mint, Edelminze

Commercially cultivated for essential oil ('Scotch spearmint oil', CAS 8008-79-5, FEMA 4221).

= M. arvensis × M. spicata
[Tucker, Arthur O., and David E. Fairbrothers. „The origin of Mentha X gracilis (Lamiaceae). I. Chromosome numbers, Fertility, and three morphological characters: De oorsprong van Mentha x gracilis (Lamiaceae). I. Chromosomen Aantallen, Fertiliteit, en Drie Morphologische Kenmerken.“ Economic Botany 44.2 (1990): 183-213]

„Dihydrocarvyl-, Neodihydrocarvyl-; trans-carvyl-, cis-carvyl-and 3-octyl-β-D-glucosides were extracted from the aboveground plant material of Mentha gentilis f. cardiaca“
[Shimizu, Sumio, et al. „Carvyl-and dihydrocarvyl-β-D-glucosides in spearmint (Studies on terpene glycosides in Mentha plants, Part II).“ Journal of Essential Oil Research 2.2 (1990): 81-86]

A small (basic) part of the oil (10ppm) contained pyridine derivatives. „Among them, 2-acetyl-4-isopropenylpyridine is a major component and has a powerful grassy-sweet and minty odor.“
[Ishihara, Masakazu, et al. „New pyridine derivatives and basic components in spearmint oil (Mentha gentilis f. cardiaca) and peppermint oil (Mentha piperita).“ Journal of agricultural and food chemistry 40.9 (1992): 1647-1655]

Acidic volatile components in Midwest Scotch spearmint oil (Mentha gracilis Sole) were 11 phenols and 35 carboxylic acids including cis-2-pentylcyclopropane-1-carboxylic acid.
[Tsuneya, Tomoyuki, et al. „Acidic components in Scotch spearmint oil (Mentha gracilis Sole).“ Journal of Essential Oil Research 10.5 (1998): 507-516]

The essential oil of M.cardiaca cv.MCAS-2 contained mainly carvone (49.4-74.0%) and limonene (2.6-32.8%) at all developement stages. Minor components were 1,8-cineole (0.2-2.1%), 3-octanol (0.8-1.8%), menthone (0.1-0.2%), isomenthone (0.1-0.4%), menthyl acetate (0.1-0.2%), terpinen-4-ol (0.1-3.3%), neomenthol (0.1-0.2%), and menthol (0.1-4.2%).
[Bahl, J. R., et al. „Quality evaluation of the essential oils of the prevalent cultivars of commercial mint species Mentha arvensis, spicata, piperita, cardiaca, citrata and viridis cultivated in Indo-Gangetic plains.“ Journal of Medicinal and Aromatic Plant Sciences 22.1B (2000): 787-797]

Like in spearmint oil (from M.spicata, carvone found 73.2%), the carvone content of M.cardiaca is also 60-70% (found here 60.9%). But M.cardiaca typically has a higher limonene content of up to 20 % (found 21.5%; M.spicata 7.5%). High menthone content (M.cardiaca 1.3%; M.spicata 0%) was recognized as an prime indicator of Scotch spearmint oil. Minor components were also 1,8-cineole (2.2%), cis-carveol (1.4%), and β-myrcene (1.1%).
[Chowdhury, Jasim Uddin, et al. „Chemical constituents of essential oils from two types of spearmint (Mentha spicata L. and M. cardiaca L.) introduced in Bangladesh.“ Bangladesh Journal of Scientific and Industrial Research 42.1 (2007): 79-82]
https://www.banglajol.info/index.php/BJSIR/article/download/359/354

Major components of the essential oil of M.cardiaca were carvone (59.6%) and limonene (23.3%) followed by β-myrcene (2.5%), 1,8-cineole (2.1%), cis-dihydrocarvone (1.5%), and β-bourbonene (1.5%).
„In view of strong antifungal activity against moulds causing biodeterioration of dry fruits and ability to surpress aflatoxin secretion and free radical genreation as well as favourable safety profile, the M.cardiaca EO may be recommended as plant based shelf life enhancer of stored food commodities“.
[Dwivedy, Abhishek Kumar, et al. „Chemically characterized Mentha cardiaca L. essential oil as plant based preservative in view of efficacy against biodeteriorating fungi of dry fruits, aflatoxin secretion, lipid peroxidation and safety profile assessment.“ Food and Chemical Toxicology 106 (2017): 175-184]