- Latin synonyms: Satureja vulgaris, Acinos vulgaris
- Family: Mint Family – Lamiaceae (Labiatae)
- Growing form: Perennial herb. With subterraneous runners.
- Height: 20–60(–80) cm (8–25(–30) in.). Stem often unbranched, 4-edged, hairy. With weak fragrance.
- Flower: Corolla irregular (zygomorphic), crimson, 10–20 mm (0.4–0.8 in.) long, fused, bilabiate, long-tubed, upper part hairy. Upper lip flat, with notched tips; lower lip 3-lobed, central lobe slightly larger than lateral lobes, with notched tips–2-lobed. Calyx cylindrical, curving, with narrow base, bilabiate, 11–13-veined, 5-lobed, 3 lobes on upper lip shorter than lobes on lower lip. Stamens 4, of which 2 long and 2 short. Gynoecium composed of 2 fused carpels. Inflorescence a dense, spike-like cluster comprised of separate axillary whorls, terminating stem.
- Leaves: Opposite, short-stalked. Blade ovate–elliptic, with entire margins or shallow and blunt teeth, both sides hairy. Inflorescence’s subtending bracts like stem leaves.
- Fruit: 4-parted schizocarp. Mericarps spherical, glossy, yellowish brown.
- Habitat: Broad-leaved forests, grove-like forests and hedgerows, meadows, dry meadows, meadows, banks. Calciphile.
- Flowering time: July–August.
Wild basil grows in the south of Finland in nutritious, light-filled areas, most commonly on the Åland Islands and in the south-west of the country, although it also grows inland. There is a divide between these habitats, which is thought to demonstrate that wild basil has arrived in Finland by two different routes: from the south-west and the south-east. It is thus a native plant on the margins of broad-leaved forests, on rich meadows, and on calciferous rocky outcrops. The species exploited grazing slash-and-burn agriculture to great effect, but it shuns contemporary cultural environments, unlike its close relative basil-thyme (C. acinos), which thrives better beside rocks. The species are quite alike both with regards to appearance and demands to such an extent that they often share the same habitat and grow side by side. Basil-thyme is smaller and shorter-lived, and it also demands a more open habitat than wild basil. The species can be differentiated from each other on the basis of e.g. basil-thyme’s strong aroma. Wild basil has a weak fragrance and actually looks quite like thyme. Despite its name, wild basil is not used in the kitchen. Additionally, basil-thyme’s corolla is purplish and clearly smaller than its relatives, being under 10 mm (0.4 in.) across.
A look-alike plant that might be found growing especially on the outskirts of inhabited areas is Large-flowered calamint (Showy calamint, Mint savory, Clinopodium grandiflorum, also Satureja grandiflora), which sometimes escapes from gardens. It resembles wild basil, but is exceptionally large-flowered as the name says. At least from the pollinators’ point of view it and also wild basil have large flowers: only long-tongued bumblebees, honeybees and butterflies can reach down to access the nectar. Dry wild basil stems remain erect to a certain extent throughout the winter: the fruit and seeds can remain above snow level and spread on the wind. Usually a whole inflorescence whorl spreads as a unit.