Acinos is a genus of flowering plants in the mint family (Lamiaceae, order Lamiales), historically recognized as a distinct genus but now included by most authorities within Clinopodium sensu lato. The genus contains a single widely recognized species, Acinos alpinus (rock thyme, also known as Clinopodium alpinum). Rock thyme is a low-growing perennial herbaceous chamaephyte, reaching 40–50 cm in height, with woody, fuzzy stems and opposite, ovoid-to-lanceolate leaves 5–15 mm long on thin petioles. Its hermaphroditic violet flowers are borne in whorled inflorescences of 3–8, each 15–20 mm in length, blooming between May and August depending on altitude. The fruit is schizocarpal, splitting into four equal nutlets at maturity, and the plant is anchored by a taproot with a network of secondary roots. Acinos belongs to a large and complex clade within subtribe Menthinae that also includes the New World mints Hedeoma, Monarda, and Pycnanthemum, forming a sister group to Mentha.
Taxonomy
Acinos was historically recognized as a separate genus within Lamiaceae (mint family, subtribe Menthinae), but modern taxonomic revisions have subsumed it into a broadly defined Clinopodium sensu lato, along with Calamintha, Micromeria, Satureja, and Xenopoma. This broad circumscription was shown to be polyphyletic by Bräuchler et al. (2004, 2010). Within the expanded Clinopodium, the former Acinos species form the “Clinopodium acinos group,” a clade allied to Ziziphora. The Clinopodium complex awaits systematic revision before valid names can be conclusively designated. GBIF continues to accept Acinos at genus rank with one descendant species.
Distribution
Acinos alpinus is native to the mountains of Southern Europe, with populations documented in the Italian Alps and similar ranges at elevations between 900 and 2,600 meters above sea level. It grows in open fields, rock fissures, and areas with thin, infertile soils typical of alpine and subalpine habitats.
Ecology
Acinos alpinus is classified as a chamaephyte (specifically a chamaephyte sufruticosos) under the Raunkiær plant life-form system, with overwintering buds borne close to the ground — an adaptation to alpine conditions. Its flowers bloom between May and August depending on altitude, and it occupies open, rocky habitats with little fertile soil. Clinopodium species (including the former Acinos) serve as larval food plants for Lepidoptera including Coleophora albitarsella.
Cultural Uses
In traditional pharmacology, rock thyme (Acinos alpinus / Clinopodium alpinum) is used for its diaphoretic (sweat-inducing) and antipyretic (fever-reducing) properties, and can be brewed as an herbal tea. Related Clinopodium species have broader medicinal use — for example, C. macrostemum is consumed in Mexico as a tea called poleo or yerba de borracho to treat hangovers, stomach aches, and liver disease.
