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Mentha aquatica × M. spicata (M.
× piperita L.), Peppermint

Account Summary

Introduction, naturalised garden escape, very rare, but possibly or probably overlooked to some extent.

1934; Praeger, R.Ll.; shore of Lower Lough Erne near Enniskillen.

Growth form and preferred habitats

M. × piperita is a very variable hybrid ± intermediate between its parents. Like Mentha arvensis × M. spicata (M. × gracilis) (Bushy Mint), it is the sterile product of interbreeding between a native and an introduced mint species and, therefore, it might occur both spontaneously (very rarely) and more often as a garden escape or discard (R.M. Harley, in: Stace et al. 2015). Leaves give off a pungent smell and taste of peppermint or lemon when crushed. Glabrous plants are generally believed to be of garden origin, while pubescent ones are considered more likely to be spontaneous hybrids arising in the wild. These two forms are often not distinguished by field recorders and the true picture is, therefore, unknown (K. Walker, in: Preston et al. 2002).

Peppermint usually grows in marshes and wet grassland on the margins of lakes, ponds, rivers and streams, as well as by artificial habitats such as ditches, reservoirs and canals. It is also found by roadsides, near habitation and by abandoned buildings on waste ground and in places where garden waste material is dumped. Well established populations may be large and long persistent, since although the plants are sterile, they have vigorous hybrid growth (heterosis) and strong colonising ability due to their creeping rhizomes (R.M. Harley, in: Stace et al. 2015).

Variation

Sell & Murrell (2009) distinguish four varieties on the basis of leaves with or without crisped margins, inflorescence shape (oblong spike versus globose head) and hairiness of pedicels and calyx.

Fermanagh occurrence

There are only four records for this familiar, but very variable garden hybrid mint in the Fermanagh Flora Database.

With so very few records in the current Fermanagh survey, it is very possible that M. × piperita is being overlooked and under-recorded to some extent. Peppermint has not been recorded in Fermanagh by anyone since 1975.

The local habitats for this vigorous, rhizomatous perennial are perfectly typical of elsewhere in these islands – in damp to wet waste ground near habitation, in ditches and on lakeshores. The details of the other three Fermanagh records are: S of Lisnaskea, Upper Lough Erne, 1950, MCM & D; near Corraslough Point, by Derryvrane L.O.L. (Loyal Orange Lodge) Hall, Upper Lough Erne, 1950, MCM & D; River Erne at Enniskillen, 18 August 1975, Mrs C.R. Hackney & P. Hackney, voucher in BEL.

Irish occurrence

Elsewhere in Ireland, M. × piperita is an occasional garden escape, growing and sometimes persisting for long periods in damp places on river and canal banks, roadsides and near houses. The Cen Cat Fl Ir 2 and Cat Alien Pl Ir together indicate that this hybrid has been found at least once in 39 of the 40 Irish VCs, the exception being Co Meath (H22). The New Atlas hectad map coverage, on the other hand, shows that Peppermint is scarce across most of S Ireland, with widely scattered recent records only, but it is somewhat more frequently and consistently recorded in NI.

British occurrence

As the New Atlas hectad map shows, M. × piperita is widely scattered throughout lowland Britain from S to N, including a presence in both Orkney (VC 111) and Shetland (VC 112) (Preston et al. 2002). The high proportion of pre-1970 records in the New Atlas from E England suggests the hybrid has declined in that area, probably reflecting the loss of casual or naturalised populations that arose from the previous (now gone) commercial scale cultivation of Peppermint that took place in that part of the country (K. Walker, in: Preston et al. 2002).

European and world occurrence

Peppermint is widespread in temperate Europe and the Middle East, both as a spontaneous hybrid and as a garden escape or discard. It has been very widely introduced and cultivated worldwide for its culinary and many medicinal uses (Sell & Murrell 2009). Most commercial Peppermint oil production takes place now in The United States of America and in Morocco (R.M. Harley, in: Stace et al. 2015).

Uses

M. × piperata is one of the most important sources of the volatile oil of Peppermint distilled from the plant and it has been cultivated as such for many centuries for use as a flavouring and therapeutic agent. According to Pliny, Peppermint was used by the ancient Greeks and Romans to flavour both their food and wine. While there is evidence of ancient medicinal use in Egypt and in Iceland in the 13th century (!), Peppermint only came into general use in western medicine around the mid-18th century and then was first used, and commercially cultivated, in England (Grieve 1931).

Peppermint is regarded as the most important essential oil available to herbal medicine, the chief constituent of which is menthol, although it also contains menthyl acetate (an ester that gives the oil most of its characteristic minty odour), isovalerate, menthone, cineol and limonene. The oil is contained in numerous brands of proprietary medicines such as tinctures, salves, essences, inhalants, herbal pills, toothpaste and tea-mixtures (Launert 1981).

Peppermint oil is more anti-spasmodic than any other volatile oil and adds greatly to its power to relieve pains arising in the alimentary canal. Its stimulating, stomachic and carminative properties are valuable in treating dyspepsia, being mostly used for flatulence and colic. Oil of Peppermint helps treat sickness and nausea and it is also used to disguise unpalatable drugs. Peppermint tea is useful in combating the early stage of colds, sometimes effecting a cure. Menthol is used to relieve the pain of rheumatism, neuralgia, throat affections and toothache. It acts as a powerful local anaesthetic, vascular stimulant and disinfectant. It is inhaled for chest complaints and nasal catarrh, laryngitis and bronchitis. It is even used to ease or prevent sea-sickness (Grieve 1931).

Threats

None.