- Name also: Wild Mint, Field Mint
- Family: Mint Family – Lamiaceae (Labiatae)
- Growing form: Perennial herb. Rootstock creeping, with many runners.
- Height: 10–30 cm (4–12 in.). Stem erect–ascending, unbranched–branching, 4-edged, hairy, often reddish.
- Flower: Flowers bisexual or unisexual pistillate. Corolla slightly zygomorphic, purple, approx. 4 mm (0.16 in.) long, fused, 4-lobed, hairy. Uppermost lobe broader than others, with notched tips. Bisexual-flowered corolla clearly longer than calyx, unisexual corolla only slightly longer. Calyx campanulate (bell-shaped), 5-lobed, unclearly 5-veined, sparsely haired, with oil-secreting glands. Lobes equilaterally triangular. Stamens 4, almost same length, sometimes not developing. Gynoecium composed of 2 fused carpels. Inflorescence composed of separate, dense, abundantly-flowered axillary whorls, crown with small rosette.
- Leaves: Opposite, stalked, hairy. Leaf blade ovate–elliptic, with blunt or quite tapered tip, with tapered base, hairy, margin shallow-toothed.
- Fruit: 4-parted schizocarp. Mericarps yellowish brown, with almost glossy surface.
- Habitat: Shores, shore meadows, springs, stream banks, ditches, fields, waste ground, gardens.
- Flowering time: July–August.
Corn mint is a very diverse species. It grows on the south-western coast, by the Saimaa lakes and on Lapland river-banks, and it looks totally different every time. Variations that grow in gardens and other places that humans have influenced add to the diversity of the species. Corn mint is sometimes unofficially divided into several subspecies. Although these are not recognized botanically, they show how diverse the plant is and how interested people are in it.
Corn mint’s leaves can be used in the kitchen, but there are big differences in the flavour of different stands. Mint species cross-breed easily with each other, and hybrids between corn mint and other mints have produced a number of hybrids that are very hardy in the extreme Finnish climate. Hybrids between corn mint and other mints that grow in Finland (with different mutations) are M. x gracilis, M. x dalmatica and M. x verticillata. Altogether there are dozens of species and hybrids of mint, many of which have ancient historical uses and a place in folklore.
Water mint (M. aquatica) is another native mint species in Finland. It can be easily differentiated from its relatives and often even from hybrids by its hemispherical terminal inflorescence.