Japanese Mint
Mentha arvensis piperascens
Family: Lamiaceae or Labiatae
What it is like
Mentha arvensis piperascens is a PERENNIAL growing to 0.5 m (1ft 8in) by 1 m (3ft 3in). See above for USDA hardiness. It is hardy to UK zone 4 and is not frost tender. It is in flower from May to October, and the seeds ripen from July to October. The species is hermaphrodite (has both male and female organs) and is pollinated by Bees. It is noted for attracting wildlife. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils and can grow in heavy clay soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist soil.
Height (m): 0.5
Where it is found
Wet grasslands near rivers and lakes at elevations of 200 - 1100 metres in China.
E. Asia - China, Japan and Korea.
Conservation Status:
Countries/locations it is found in
How it is used
Food
Rating: 3
Leaves - raw or cooked. Used as a flavouring in salads or cooked foods, they have a strong taste of peppermint. A herb tea is made from the fresh or dried leaves. An essential oil from the plant is used as a flavouring in sweets and beverages. The leaves contain about 0.2% essential oil.
Condiment: the various plants that are used as flavourings, either as herbs, spices or condiments.
Tea: the various herb teas that can be used in place of tea, plus the genuine article.
Medicine
Rating: 2
Japanese mint, like many other members of this genus, is often used as a domestic herbal remedy, being valued especially for its essential oil which has antiseptic properties and a beneficial effect on the digestion. Like other members of the genus, it is best not used by pregnant women because large doses can cause an abortion. The whole plant is anaesthetic, antiphlogistic, antispasmodic, antiseptic, aromatic, carminative, diaphoretic, emmenagogue, galactofuge, refrigerant, stimulant, stomachic and vasodilator. A tea made from the leaves has traditionally been used in the treatment of fevers, headaches, digestive disorders and various minor ailments. The leaves are a classical remedy for stomach cancer. The essential oil in the leaves is antiseptic, though it is toxic in large doses.
Anaesthetic: Numbs the feeling in a local or general area of the body.
Antiphlogistic: Reduces inflammation.
Antiseptic: Preventing sepsis, decay or putrefaction, it destroys or arrests the growth of micro-organisms.
Antispasmodic: Relaxes muscular spasms and cramps, calming nervous irritation.
Aromatic: Having an agreeable odour and stimulant qualities.
Cancer: Used in the treatment of cancer.
Carminative: Reduces flatulence and expels gas from the intestines.
Diaphoretic: Induces perspiration.
Emmenagogue: Promotes or increases the menstrual flow. In early stages of pregnancy it can induce an abortion.
Febrifuge: Reduces fevers.
Galactofuge: Stops or reduces the flow of milk in a nursing mother.
Salve: Soothes and heals damaged skin.
Stimulant: Excites or quickens activity of the physiological processes. Faster acting than a tonic but differing from a narcotic in that it does not give a false sense of well-being.
Stomachic: Aids and improves the action of the stomach.
Other
Rating:
The plant is used as an insect repellent. Rats and mice intensely dislike the smell of mint. The plant was therefore used in homes as a strewing herb and has also been spread in granaries to keep the rodents off the grain. An essential oil is obtained from the plant. It can be used as a substitute for, or adulterant of, peppermint oil. Yields of up to 1.6% have been obtained.
Essential: Essential oils that are used in perfumery, medicines, paint solvents, insect repellents etc.
Repellent: Plants that are said to deter but not necessarily kill various mammals, birds, insects etc.
Strewing: Plants, usually aromatic, that are strewn on the floor to give a nice smell, repel insects etc.
Attracts Wildlife: Plants noted for attracting wildlife
Scented Plants: Plants noted for their scent
How it is grown
An easily grown plant, it succeeds in most soils and situations so long as the soil is not too dry. This species tolerates much drier conditions than other members of the genus. Prefers a slightly acid soil. Grows well in heavy clay soils. A sunny position is best for production of essential oils, but it also succeeds in partial shade. Plants are hardy to at least -15°c. Most mints have fairly aggressive spreading roots and, unless you have the space to let them roam, they need to be restrained by some means such as planting them in containers that are buried in the soil. The whole plant has a very strong scent of peppermint. Hybridizes freely with other members of this genus. Polymorphic. The flowers are very attractive to bees and butterflies. A good companion plant for growing near brassicas and tomatoes, helping to deter insect pests. Members of this genus are rarely if ever troubled by browsing deer.
Propagating it: Seed - sow spring in a cold frame. Germination is usually fairly quick. Prick out the seedlings into individual pots when they are large enough to handle and plant them out in the summer. Mentha species are very prone to hybridisation and so the seed cannot be relied on to breed true. Even without hybridisation, seedlings will not be uniform and so the content of medicinal oils etc will vary. When growing plants with a particular aroma it is best to propagate them by division. Division can be easily carried out at almost any time of the year, though it is probably best done in the spring or autumn to allow the plant to establish more quickly. Virtually any part of the root is capable of growing into a new plant. Larger divisions can be planted out direct into their permanent positions. However, for maximum increase it is possible to divide the roots up into sections no more than 3cm long and pot these up in light shade in a cold frame. They will quickly become established and can be planted out in the summer.
Best place to grow: Woodland Garden Sunny Edge; Dappled Shade; Shady Edge; Cultivated Beds;
Habit: Perennial
Hardiness: 4-8
Growth:
Soil: Light (sandy), medium, heavy (clay)
Shade: Semi-shade, no shade
Moisture: Moist
Things to keep in mind
Although no records of toxicity have been seen for this species, large quantities of some members of this genus, especially when taken in the form of the extracted essential oil, can cause abortions so some caution is advised.