Peppermint (Mentha × piperita) is a (usually) sterile hybrid mint, a cross between Watermint (Mentha aquatica) and Spearmint (Mentha spicata). It is occasionally found wild with its parent species in central and southern Europe, but the first intentional crossbreed of Watermint and Spearmint was done in England. Being sterile, it spreads by rooting.

The stems are from 30-70 cm tall, rarely up to 100 cm, smooth, and square in cross section. The leaves are from 4-9 cm long and 1.5-4 cm broad, dark green with reddish veins, and with an acute apex and coarsely toothed margins. The flowers are purple, 6-8 mm long, with a four-lobed corolla about 5 mm diameter; they are produced in whorls around the stem, forming thick, blunt spikes. Flowering is from July to September.

Uses

Peppermint has a high menthol content, and is often used as a flavouring in tea, ice cream, confectionery, chewing gum, and toothpaste. The oil also contains menthone and menthyl esters. It is the oldest and most popular flavour of mint-flavored confectionery. Peppermint can also be found in some shampoos and soaps, and when used, gives the hair a minty scent and cooling sensation on the skin.

Peppermint, like many spices and herbs, is believed to have medicinal properties when consumed. It is said that it helps against upset stomachs, inhibits the growth of certain bacteria, and can help smooth and relax muscles when inhaled or applied to the skin. Other health benefits are attributed to the high manganese, vitamin C and vitamin A content; as well as trace amounts of various other nutrients such as fibre, iron, calcium, folate, potassium, tryptophan, magnesium, omega-3 fatty acids, riboflavin, and copper.

Peppermint oil has been demonstrated to reduce colicky abdominal pain due to irritable bowel syndrome (IBS) with an NNT (number needed to treat) around 3.1[1], but the oil is irritant to the stomach in the quantity required and therefore needs wrapping for delayed release in the intestine. Peppermint relaxes the gastro-oesophageal sphincter, thus promoting belching.

Peppermint flowers are heavy nectar producers and honeybees as well as other nectar harvesting organisms forage them heavily. A mild, pleasant varietal honey can be produced if there is sufficient acreage of plants.

Areas of North America where peppermint was formerly grown for oil (now produced synthetically) often have an abundance of feral plants, and it is considered somewhat invasive.

Cultivation

Peppermint generally thrives in shade and expands quickly by underground rhizomes. If you chose to grow Peppermint, it is advisable to plant it in a container, otherwise it can rapidly take over a whole garden. It needs a good water supply, and is ideal for planting in part-sun to shade areas.

The leaves and flowering tops, collected as soon as the flowers begin to open and carefully dried, are the useable portion of the plant. The wild form of the plant is less suitable for this purpose, with cultivated plants having been selected for more and better oil content.