Mentha longifolia is a very variable species with over 150 synonyms. It is generally treated as comprising of a number of subspecies and variieties, though the number and their limits are not generally agreed upon. At present (2019) there are more than 20 subspecies and varieties that are accepted (though opinions can vary as to whether they are subspecies or varieties). We have tried to include the various taxons below that seem to be in use, and have also tried to include a general list of synonyms, but acknowledge that it is incomplete.

Common Name: Horsemint

General Information

Mentha longifolia is a perennial plant that can grow up to 1.00 metres tall.
It is harvested from the wild for local use as a food, medicine and source of materials.
Various forms of horsemint are cultivated for their use as flavourings, sources of essential oil etc, and as a medicinal plant.

Known Hazards

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.

Botanical References

Range

Central and southern Europe, including Britain, Mediterranean region, Siberia.

Habitat

Waste places and damp roadsides[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Perennial
Height	1.00 m
Pollinators	Bees, Lepidoptera, Insects
Cultivation Status	Cultivated, Wild

Cultivation Details

Mentha longifolia is a moderately cold-hardy plant, able to tolerate temperatures down to around -20°c when fully dormant[].
An easily grown plant, it succeeds in most soils and situations so long as the soil is not too dry[, ]. Grows well in heavy clay soils. A sunny position is best for production of essential oils, but the plants also succeed in partial shade.
Mentha longifolia is a very varable species and is generally treated as comprising several varieties and subspecies. Botanists often do not agree with each other over the best way to treat the species, but the following list of subspecies are generally accepted. They can vary quite widely from each other in the composition of essential oils, and therefore the flavour, aroma and specific uses of the plants, but generally have more or less similar uses.
Mentha longifolia var amphilema Briq. ex Rech.f. Native to western Asia, found in Afghanistan, Iran, Iraq.
Mentha longifolia var asiatica (Boriss.) Rech.f. Native to southwestern and central Asia to Himalayan regions of China.
Mentha longifolia var austroafghanica Rech.f. Native only to Afghanistan.
Mentha longifolia subsp calliantha (Stapf) Briq. Native to western Asia, found in eastern Turkey and northern Iran. This is not always seen as distinct and is sometimes included in Mentha longifolia typhoides.
Mentha longifolia subsp capensis (Thunb.) Briq. Native to southern Africa, found from southern Namibia and southern Zimbabwe to the Cape.
Mentha longifolia subsp caucasica Briq. Restricted, as the name implies, to the Caucasus where it is both native and cultivated.
Mentha longifolia var chlorodictya Rech.f. Native to southwest Asia in Afghanistan, Iran, Iraq, Transcaucasus and Turkmenistan
Mentha longifolia subsp hymalaiensis Briq. Native to the Himalayas from Afghanistan through Pakistan and western India to Nepal.
Mentha longifolia var kermamensis Rech.f. Native only to Iran.
Mentha longifolia var kotschyana (Boiss.) Briq. Native to southwest Asia in eastern Turkey and Iran.
Mentha longifolia subsp longifolia Widely spread through Europe and Russia to western Siberia, Himalayas, northern and eastern Africa.
Mentha longifolia subsp minutiflora (Borbás ex A. Kern.) Briq. Native to Europe, where it is found in Hungary, Mecedonia and Greece.
Mentha longifolia var muqarrabica Shinwari & Chaudhri. Native to Pakistan.
Mentha longifolia subsp noeana (Briq.) Briq.Native to Turkey.
Mentha longifolia var petiolata Boiss. Southwest Asia from northern Iraq to northern and western Iran.
Mentha longifolia subsp polyadenia (Briq.) Briq. Native to southeastern southern Africa.
Mentha longifolia var schimperi (Briq.) Briq.Western Asia - Egypt (Sinai), Saudi Arabia.
Mentha longifolia var swatica Shinwari & Chaudhri. E. Asia - Pakistan
Mentha longifolia subsp typhoides (Briq.) Harley. Eastern Mediterranean to Iran.
Mentha longifolia subsp wissii (Launert) Codd. Southern Africa, Namibia, S. Africa
Sometimes cultivated for its leaves, there are some named varieties[].
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[].
Hybridizes freely with other members of this genus.
The whole plant has a mint-like aroma.
Members of this genus are rarely if ever troubled by browsing deer[].

Edible Uses

Leaves - raw or cooked. Peppermint-scented, they are used as a flavouring in salads, chutneys and cooked foods[, ].
A herb tea is made from the leaves[].
An essential oil obtained from the leaves and flowering tops is used as a food flavouring in sweets etc[]. A peppermint-like taste[].

Medicinal

Horsemint, like many other members of this genus, is often used as a domestic herbal remedy, being valued especially for its antiseptic properties and its 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 leaves and flowering stems are antiasthmatic, antispasmodic, carminative and stimulant[, , ]. 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 harvested as the plant comes into flower and can be dried for later use[].
The essential oil in the leaves is antiseptic, though it is toxic in large doses[].

Agroforestry Uses:

Mint species are usually good bee and butterfly attractant plants, supplying them with good quality pollen and nectar[]
Mints are usually quite aromatic plants and they make good companions for cabbages and tomatoes, their aromatic nature helping to repel insect pests..

Other Uses

The leaves contain about 0.57% essential oil[]. It is sometimes used as a substitute for peppermint oil in confectionery[].

Rats and mice intensely dislike the smell of mint. Members of the genus have therefore often been used in homes as strewing herbs and have also been spread in granaries to keep rodents off the stored grain[].

Propagation

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.