Asarina is a monotypic genus of flowering plants in the family Plantaginaceae (plantain family), order Lamiales, comprising a single accepted species: Asarina procumbens Mill., commonly known as the trailing snapdragon. The genus was originally placed in the Scrophulariaceae (figwort family) but was transferred to Plantaginaceae following molecular phylogenetic revisions. What was once a broader genus has been substantially reorganised: species from North America formerly assigned to Asarina have been moved to the related genera Holmgrenanthe, Lophospermum, Mabrya, Maurandya, and Neogaerrhinum. Asarina is now considered exclusively an Old World genus.
Asarina procumbens is a foetid, strongly pubescent, viscid subshrub of trailing or mat-forming habit, rarely exceeding 10–20 cm in height. The somewhat woody main stems produce lax creeping or cascading branches bearing opposite, long-petioled, hairy, lobed, reniform-to-cordate leaves with crenate, often red-tinged margins. Flowers are borne solitarily or in short racemes of two or three in the leaf axils; they are fragrant, cream-coloured with faint violet striations on the corolla tube, and pollinated by bumblebees. The fruit is a dry, glabrous, subglobose capsule that dehisces at the apex; seeds are small, brownish-buff, and distributed by epizoochory — sticky fruiting calyces attach to the fur of mammals or feathers of birds, allowing seeds to trickle from the open capsules.
The species is native to France and Spain, with its strongholds in the Pyrénées-Orientales and the Massif Central (notably the Cévennes), and has been introduced in Germany, Switzerland, Austria, and Hungary.
Etymology
The name Asarina derives from the Spanish/Latin vernacular name historically applied to this plant. The species epithet procumbens is Latin for "lying down" or "prostrate," reflecting the trailing, mat-forming growth habit of the plant.
Distribution
Asarina procumbens is native to France and Spain, where it occurs in the Pyrenean region and the Massif Central, including the Cévennes and Pyrénées-Orientales. In France it is rarely found below 400 m altitude, with an upper limit of around 1800 m; it has protected status in the Auvergne region. The species has been introduced in Germany, Switzerland, Austria, and Hungary.
Ecology
Asarina procumbens is a semi-evergreen alpine chasmophyte, specialising in crevices of silica-rich, non-sedimentary rocks (granite, diorite, gneiss, schist, quartzite) in partial shade. This habitat — "Mediterranean siliceous inland cliff" — carries the European Red List of Habitats code H3.1d, indicating a threatened habitat type. Low-altitude occurrences face pressures from road and railway cliff stabilisation, rock-climbing, quarrying, and invasive species. The plant is pollinated by bumblebees, and seeds are dispersed by epizoochory via sticky fruiting calyces.
Cultivation
Asarina procumbens thrives in somewhat dry partial shade with well-drained, sandy or gravelly, humus-rich soil; it dislikes excessive winter wetness. It blooms most freely where summers are not excessively hot. The plant is evergreen in mild climates but may be killed by heavy frost, after which it can be propagated from self-sown seed, as it self-seeds readily. Useful as a trailing alpine or ground-cover plant, and it thrives as a container specimen. Pruning is rarely needed but the plant may be cut back in autumn if foliage is spent. Hardiness: UK H3; USDA zones 8, 9, and 10.
Taxonomy Notes
Asarina was historically placed in Scrophulariaceae and treated as a broader genus encompassing many New World trailing vines. Molecular phylogenetic work led to its transfer to Plantaginaceae and the redistribution of its North American members to Holmgrenanthe, Lophospermum, Mabrya, Maurandya, and Neogaerrhinum. The genus is now monotypic and confined to the Old World.
