Commonly called mint, plants of the genus Mentha grow throughout the world with species on all continents except Antarctica. Most species of wild mint follow a perennial growth cycle, renewing themselves through stolons, or horizontally spreading stems, which make them prolific -- although potentially invasive -- in areas with moist, partially shaded soil. Cultivated for its aromatic foliage, wild mint readily hybridises and exists in numerous man-made and naturally occurring varieties.
Native to Europe and the Middle East, spearmint (M. spicata) now grows across much of Asia, the Americas and Australia as a naturalised species. Where moist soil and dappled sunlight are present, spearmint spreads aggressively, creating dense mats of upright flowering stalks between 1 1/2 to 3 feet in height. The smooth, bright-green foliage is intensely aromatic with a spearhead-like shape and slightly serrated edges. Extensively cultivated, spearmint is used in teas and as an anti-fungal in traditional medicine.
Among the most widespread wild mint species, field mint (M. arvensis) occurs throughout the Northern Hemisphere, from Eurasia to North America. Like most mint species, field mint thrives in rich, evenly moist soil and partial sun, where it grows to between 6 and 16 inches in height. From early to midsummer, field mint blooms profusely, bearing clusters of pale lavender flowers with a strong herbal scent.
Known for its pungent peppermint-like scent, horse mint (M. longifolia) is a perennial herbaceous species common across Europe, Asia and Africa. Tall and rangy, horse mint reaches 4 feet in height under ideal conditions with slender, 4-inch-long leaves and tall stalks of pale mauve flower clusters. In traditional medicine, horse mint is used to treat respiratory ailments and digestive upsets.
Sometimes called apple mint, woolly mint (M. suaveolens) is a spreading, perennial wild mint commonly cultivated in gardens around the world. Within its native European range, woolly mint is found near seeps, in wetlands and in moist, partially shaded meadows below 1000 feet of altitude. It is identifiable by its light-green, slightly hairy foliage and 4-foot-tall flower stalks topped by showy white flower clusters. Several naturally occurring and manmade cultivars of woolly mint exist, including variegated and dwarf varieties.
Perhaps the best known species of wild mint is peppermint (M. --- piperita), a naturally occurring hybrid between water mint (M. aquatica) and spearmint (M. spicata). Native to Europe, peppermint is naturalised on every continent except Antarctica and is highly prized for its pungent fragrance, which is herbal and peppery with a cooling sensation caused by high levels of menthol. Used mainly as a flavouring aid, peppermint has medicinal value, as well, and is widely used as a treatment for gastrointestinal diseases such as irritable bowel syndrome.