Spearmint


Spearmint, also known as garden mint, common mint, lamb mint and mackerel mint, is a species of mint, Mentha spicata, native to Europe and southern temperate Asia, extending from Ireland in the west to southern China in the east. It is naturalized in many other temperate parts of the world, including northern and southern Africa, North America and South America. It is used as a flavouring in food and herbal teas. The aromatic oil, called oil of spearmint, is also used as a flavouring and sometimes as a scent.
The species and its subspecies have many synonyms, including Mentha crispa, Mentha crispata and Mentha viridis.

Description

Spearmint is a perennial herbaceous plant. It is tall, with variably hairless to hairy stems and foliage, and a wide-spreading fleshy underground rhizome from which it grows. The leaves are long and broad, with a serrated margin. The stem is square-shaped, a defining characteristic of the mint family of herbs. Spearmint produces flowers in slender spikes, each flower pink or white in colour, long, and broad. Spearmint flowers in the summer, and has relatively large seeds, which measure. The name 'spear' mint derives from the pointed leaf tips.
Mentha spicata varies considerably in leaf blade dimensions, the prominence of leaf veins, and pubescence.

Taxonomy

Mentha spicata was first described scientifically by Carl Linnaeus in 1753. The epithet spicata means 'bearing a spike'. The species has two accepted subspecies, each of which has acquired a large number of synonyms:
The plant is a tetraploid species, which could be a result of hybridization and chromosome doubling. Mentha longifolia and Mentha suaveolens are likely to be the contributing diploid species.
Mentha spicata hybridizes with other Mentha species, forming hybrids such as:
Mention of spearmint dates back to at least the 1st century AD, with references from naturalist Pliny and mentions in the Bible. Further records show descriptions of mint in ancient mythology. Findings of early versions of toothpaste using mint in the 14th century suggest widespread domestication by this point. It was introduced into England through the Romans by the 5th century, and the “Father of British Botany”, of the surname Turner, mentions mint as being good for the stomach. John Gerard's Herbal states that: "It is good against watering eyes and all manner of break outs on the head and sores. It is applied with salt to the biting of mad dogs," and that "They lay it on the stinging of wasps and bees with good success." He also mentions that "the smell rejoice the heart of man", for which cause they used to strew it in chambers and places of recreation, pleasure and repose, where feasts and banquets are made."
Spearmint is documented as being an important cash crop in Connecticut during the period of the American Revolution, at which time mint teas were noted as being a popular drink due to them not being taxed.

Ecology

Spearmint can readily adapt to grow in various types of soil. Spearmint tends to thrive with plenty of organic material in full sun to part shade. The plant is also known to be found in moist habitats such as swamps or creeks, where the soil is sand or clay.
Spearmint ideally thrives in soils that are deep and well drained, moist, rich in nutrients and organic matter, and have a crumbly texture. pH range should be between 6.0 and 7.5.

Diseases and pests

Fungal diseases

Fungal diseases are common diseases in spearmint. Two main diseases are rust and leaf spot. Puccinia menthae is a fungus that causes the disease called “rust”. Rust affects the leaves of spearmint by producing pustules inducing the leaves to fall off. Leaf spot is a fungal disease that occurs when Alternaria alernata is present on the spearmint leaves. The infection looks like circular dark spot on the top side of the leaf. Other fungi that cause disease in spearmint are Rhizoctonia solani, Verticillium dahliae, Phoma strasseri, and Erysiphe cischoracearum.

Nematode diseases

Some nematode diseases in spearmint include root knot and root lesions. Nematode species that cause root knots in this plant are various Meloidogyne species. The other nematode species are Pratylenchus which cause root lesions.

Viral and phytoplasmal diseases

Spearmint can be infected by tobacco ringspot virus. This virus can lead to stunted plant growth and deformation of the leaves in this plant. In China, spearmint have been seen with mosaic symptoms and deformed leaves. This is an indication that the plant can also be infected by the viruses, cucumber mosaic and tomato aspermy.

Cultivation

Spearmint grows well in nearly all temperate climates. Gardeners often grow it in pots or planters due to its invasive, spreading rhizomes.
Spearmint leaves can be used fresh, dried, or frozen. They can also be preserved in salt, sugar, sugar syrup, alcohol, or oil. The leaves lose their aromatic appeal after the plant flowers. It can be dried by cutting just before, or right as the flowers open, about one-half to three-quarters the way down the stalk. Some dispute exists as to what drying method works best; some prefer different materials and different lighting conditions.

Oil uses

Spearmint is used for its aromatic oil, called oil of spearmint. The most abundant compound in spearmint oil is R--carvone, which gives spearmint its distinctive smell. Spearmint oil also contains significant amounts of limonene, dihydrocarvone, and 1,8-cineol. Unlike oil of peppermint, oil of spearmint contains minimal amounts of menthol and menthone. It is used as a flavouring for toothpaste and confectionery, and is sometimes added to shampoos and soaps.

Research and health effects of spearmint oil

Spearmint has been used traditionally as medicines for minor ailments such as fevers, and digestive disorders. There is research on spearmint extracts in the treatment of gout and as an antiemetic.

Spearmint oil used as insecticide and pesticide

Spearmint essential oil has had success as a larvicide against mosquitoes. Using spearmint as a larvicide would be a greener alternative to synthetic insecticides due to their toxicity and negative effect to the environment.
Used as a fumigant, spearmint essential oil is an effective insecticide against adult moths.

Medical research

Antitumor

The main chemical component of spearmint is the terpenoid carvone, which has been shown to aid in the inhibition of tumors. Perillyl alcohol, an additional terpenoid found in lower concentrations in spearmint, positively effects the regulation of various cell substances involved in cell growth and differentiation.

Antioxidant

Studies on spearmint have shown varying results on the antioxidant effects of the plant and its extracts. Results have ranged from spearmint essential oil displaying considerable free radical scavenging activity to no antioxidant activity in spearmint essential oil, but strong activity in spearmint methanolic extract. Antioxidant activity has been shown to be significantly higher in spearmint that is dried at lower temperatures rather than high. It is suggested this is due to the degradation of phenolics at high temperatures. In experiments demonstrating antioxidant properties in spearmint oil, the major component, carvone, alone showed lower antioxidant activity.

Antimicrobial

Spearmint has been historically used for its antimicrobial activity, which is likely due to the high concentration of carvone. Its in vitro antibacterial activity has been compared to, and is even said to surpass, that of amoxicillin, penicillin, and streptomycin. Spearmint oil is found to have higher activity against Gram-positive bacteria compared to Gram-negative bacteria, which may be due to differing sensitivities to oils. The degree of antimicrobial activity varies with the type of microorganism tested.

Additional properties

Studies have found significant antiandrogen effects in spearmint, specifically following routine spearmint herbal tea ingestion. Antispasmodic effects have been displayed in spearmint oil and carvone, the main chemical component of spearmint.

Beverages

Spearmint leaves are infused in water to make spearmint tea. Spearmint is an ingredient of Maghrebi mint tea. Grown in the mountainous regions of Morocco, this variety of mint possesses a clear, pungent, but mild aroma. Spearmint is an ingredient in several mixed drinks, such as the mojito and mint julep. Sweet tea, iced and flavoured with spearmint, is a summer tradition in the Southern United States.

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