Clinopodium menthifolium (Host) Stace - syn.Calamintha officinalis (Moench) auct.; Calamintha sylvatica Bromf.; Satureja menthifolia (Host) Fritsch - Lamiaceae - wood calamint, Bergminze, Wald-Bergminze

Perennial herb, up to 80cm tall, native to Central and South Europe, Western Asia; leaves ovate, serrate; flowers purple to violet.

„The lower calyx teeth of species of the Calamintha sylvatica group have about the double length of the upper ones. Usually two species or subspecies are differed: Calamintha menthifolia (= Calamintha sylvatica subsp. sylvatica), which also occurs in Central Europe, and Calamintha ascendens (= Calamintha sylvatica subsp. ascendens). The latter has smaller blooms and shorter petioles at the flowers. “
http://www.guenther-blaich.de/pflseite.php?par=Calamintha+menthifolia

From the essential oil of Calamintha sylvatica Bromf. subsp. sylvatica, thirty-three constituents were identified at three different development stages (pre-blossom, full blossom and post-blossom). Main component was cis-piperitone oxide (66.6-74.6%), followed by isomenthone (0.6-13.4%), menthone (0.2-5.5%), cis-sabinene hydrate (2.0-4.4%), limonene (1.4-3.0%), and β-caryophyllene (1.1-4.4%). Isomenthone is significantly present in the pre-blossom phase (13.4%), in other phases its content is relatively low (1.9% and 0.6%).
[The volatile constituents of Calamintha sylvatica Bromf. subsp. sylvatica., Kitic, D., Palic, R., Ristic, M., Sojanovic, G., Jovanovic, T., Flavour and fragrance journal, Vol.16(4), 2001, 257-258]

„Essential oil yield and composition of wild and cultivated Calamintha sylvatica Bromf. ssp. ascendens (Jordan) P.W. Ball (Lamiaceae) were studied using GC and GC/MS. Essential oil yields were very similar in both conditions, although plant growth was greater in the cultivated plants. Isomenthone (36.8–43.3%) proved to be the main component of oil in both cases.“
[Essential oils in Calamintha sylvatica Bromf. ssp. ascendens (Jordan) PW Ball: wild and cultivated productions and antifungal activity., Hidalgo, P.J., Libera, J.L., Santos, J.A., LaFont, F., Castellanos, C., Palomino, A., Román, M., Journal of Essential Oil Research, Vol.14(1), 2002, 68-71]

„C.sylvatica oil yields varied from 0.11% up to 0.94%. In all samples, cis-piperitone oxide was a major compound… (48.9–59.2%). In the examined samples, oil composition appeared to vary more according to geographical rather than genetic factors.“
[Essential Oil of Calamintha sylvatica Bromf. and Calamintha vardarensis Šilic., Mimica-Dukić, N., Couladis, M., Tzakou, O., Jančić, R., Slavkovska, V., Journal of Essential Oil Research, Vol.16(3), 2004, 219-222]

„The composition of the essential oil obtained from the dried flowering aerial parts of Calamintha officinalis Moench (Lamiaceae) was analyzed by GC and GC-MS. Thirty-four components have been identified in the oil of C. officinalis. The major constituents of this oil were β-bisabolene (9.9%), germacrene D (7.6%), β-bourbonene (7.4%) and piperitenone (5.3%).“
[The Essential Oil Composition of Calamintha officinalis Moench from Iran., Morteza-Semnani, K., Akbarzadeh, M., Journal of Essential Oil Bearing Plants, Vol.10(6), 2007, 494-498]

English Botany, or Coloured Figures of British Plants, ed.3 [B] [J.E.Sowerby et al], vol.7 t.1052 (1867)
http://plantgenera.org/species.php?id_species=257357

picture source wikimedia commons (user AnRo0002, public domain)