Mint is one of the oldest spicy, aromatic and medicinal plants. Egyptian papyri indicate that as early as 1550 BC. NS. the locals used mint as a medicine. In 410 BC, i.e. 2400 years ago, the Egyptians knew the method of obtaining essential oil by hydrodistillation. Since time immemorial, mint has been used as an aromatic and medicinal plant in Japan, especially as a lotion in the treatment of eye diseases. Mint is mentioned by many medieval herbalists. But the whole catch is that these ancient sources are not talking about peppermint, but about other species: field mint, water mint and others.
Peppermint (Mentha x piperita) - a complex natural sterile hybrid from cross-pollination of spearmint and watermint (M. spicata L. xM. aquatica L.). Her year of birth is considered to be 1696, which includes a herbarium of this particular species in the collection of the British Museum, found in southern England. In 1721, it was first included in the British Pharmacopoeia. With the aim of obtaining essential oil near Mitchum in Surrey in 1796, industrial plantations of mint were established on 40 hectares. At this time, the global demand for essential oil of peppermint was 1 ton per year (for comparison: by 2012, the production of peppermint oil had grown to 4000 tonnes (80% produced in the USA) and this is not counting other types of mint grown for menthol or local use. in different parts of the world). Production grows by 5% annually.
In the 17th century, it was actively cultivated in England and it successfully began to oust other species from culture, and in other countries, first in Europe, and then in other continents. It is still called that - "English mint".
In Russia, the first English mint plantations appeared in 1893 in the Lubensky and Priluksky districts of the Poltava province on an area of 27 hectares to meet the demand for mint for kvass, tobacco and soap making. In 1913, there were already 1000 hectares under the mint, from which 10 tons of essential oil were obtained; in 1940, 180 tons of oil were produced from 11 thousand hectares.
That is why in our country, speaking of mint, the majority means exactly peppermint, which is traditionally added to teas, gatherings and even salads. We get mint oil from it, which is added as a flavoring to toothpastes and powders, and even taken orally. In addition, both the leaf and the essential oil are widely used in folk and scientific medicine, perfumery and cosmetic production, food and canning industries, in alcoholic beverages and confectionery.
But you should still start with the features of the biology of this plant.
Peppermint (Menthaxpiperita L.) is a perennial herb from the Lamb family (Lamiaceae) 80-110 cm high. Stems are branched or simple, 4-sided, erect, green (sometimes with a purple tint). The stem is highly branched, the number of stems is approximately 10-20 per 1 m2. Leaves petiolate, oblong, ovate-lanceolate, serrate at the edges, opposite in pairs. The flowers are small, from blue to purple in color, located in the axils of the bracts in opposite semi-whorls, and the whorls themselves form a spike-shaped inflorescence.
The bulk of the roots is located in the soil layer up to 30 cm. From the root collar in the upper (2-8 cm) soil layer, many rhizomes are formed, where reserve nutrients are deposited. They have thickenings - nodes from which adventitious roots and aerial shoots grow. Actually, due to them, mint multiplies. As already mentioned, it is an interspecific hybrid and therefore practically does not form seeds, well, if only single ones, and not all of them are viable.They are used for breeding work, but for industrial breeding, seed reproduction is not suitable and therefore it is not worth looking for peppermint seeds for sale, and if they are offered, then you should think about the good faith of the manufacturer.
We value mint primarily for its aroma, which is determined by the content of essential oil. The essential oil is concentrated in numerous oil glands, which consist of a 1-cell stem and an 8-cell head. There are 3 times more glands on the underside of the sheet than on the top. Their maximum number is located in the basal part of the leaf. On the underside of one sheet of the middle tier, for example, in the Prilukskaya 6 variety, there are 4-5 thousand pieces of iron, while in other varieties there are up to 10 thousand. There are 7-20 pieces of iron per 1 mm2.
But, given the great interest, wide distribution around the world, a great many varieties and forms of peppermint appeared, often quite unusual and more similar to other interspecific hybrids. And again, this question remains on the conscience of manufacturers.
As a result of breeding work, 2 forms of peppermint were identified, differing in the color of leaves, stems, the content of essential oil, and its composition:
- white mint (alba or palescens - the stems and veins of the leaf are light green, medium oily, menthol up to 60%, oil with a delicate aroma, cultivated in France, therefore it is called French;
- black mint - with anthocyanin coloration of stems and veins of leaves, the leaf is dark green, contains more essential oil, but the aroma is more pungent.
In Russia, black and intermediate forms are cultivated, and it is to this form that most varieties of domestic selection belong.
Biological bases of cultivation
As already indicated, mint is a herbaceous perennial plant. However, this position is relatively fair, since every year not only the aboveground vegetative mass, but also the underground organs - the roots of the mother plant, die off in mint, and the next year a new plant grows in the same place from the daughter rhizomes prudently laid in the soil by the mint.
In the annual cycle, mint goes through certain phases of development, which differ in duration depending on the variety and climatic conditions, but on average they are: from planting to the beginning of regrowth - 20 days; full shoots - on the 42nd day; from full germination to branching - 33 days; from branching to the beginning of budding - 17 days; budding - 23; flowering - 16 days. With the onset of the flowering phase, the growth rate naturally decreases and this moment is the optimal time for harvesting. In mint, it is possible to induce a repeated intensive vegetation, if the aboveground mass is cut off a little earlier, during the budding period - flowering. Accordingly, two cuts are obtained. But this is possible only in the southern regions, in the Moscow region the second mowing will have to be done in autumn and, firstly, it will greatly weaken the plants, and secondly, the harvest will be “not very good” - in cold weather the essential oil accumulates very badly.
Not all mint organs are created equal. Thus, the inflorescences contain a lot of oil, but its quality is worse in comparison with the oil from the leaves because of the significant amount of mentofuran and the low content of menthol. In turn, the upper leaves contain more essential oil and less menthol. Based on this, when growing mint, you need to create conditions for the growth and preservation of the leaves. For example, with thickened plantings and a lack of nutrition, the lower leaves quickly begin to die off and the plant is nourished at their expense. In such a crop, there are many low-value stems.
Rhizomes are formed in the soil layer 0-8 cm; on the lungs, they lie deeper, on heavy, waterlogged ones - smaller or even come to the surface and turn into green whips. And it is on the surface that the danger of perishing lies in wait for them. Therefore, loose soils are recommended for mint, where nothing "squeezes" the rhizomes. The most acceptable are chernozems, medium loams, rich in organic matter, as well as peatlands, but not swampy soils.Heavy clayey, floating, saline soils are unsuitable. The permissible pH range is 5-8, the optimum is 6-7.
On nitrogen-rich soils, the yield is higher, but the aroma of the oil is worse due to the accumulation of menthone, which has the smell of "rancid" peppermint oil. In addition, excess nitrogen contributes to the development of rust. Phosphorus smoothes out the negative effect of nitrogen, while the amount of menthol increases. An excess of potassium leads to an increase in menthone content and a decrease in menthol content, especially in peatlands. Boron and zinc, magnesium and cobalt with foliar feeding contribute to the accumulation of essential oil.
In mint of the first year, before the beginning of budding, the length of the rhizomes is equal to the length of the lateral branches. Later, they spread up to 70 cm, forming 30-50 nodes. Each node contains vegetative buds. When planted with whole rhizomes, only 7-20% of the buds germinate. By dividing the rhizomes, you can increase the number of seedlings, but their viability decreases, which depends on the supply of plastic substances in the segments. Therefore, grinding rhizomes before planting is allowed into segments at least 15 cm long, and if watering is possible, at least 8 cm.
The middle and apical parts of the plant are richer in plastic substances. Buds from the nodes of the lower part rarely sprout. The bulk of rhizomes is formed after the budding phase, i.e. the later the aboveground harvesting is carried out, the more rhizomes for planting next year. With a lack of moisture, rhizomes are formed much less.
Rhizomes of mint do not have a period of deep winter dormancy; during winter thaws, they sometimes start growing, which can lead to their death. Interestingly, the rhizomes of plants with unharvested aboveground mass are distinguished by a deeper winter dormancy, which, apparently, is due to the synthesis of inhibitors of the vital activity of rhizomes in the inflorescences.
Mint is a moisture-loving plant. Scientists have calculated that 1500 m3 of water is consumed for the formation of 1 ton of leaf during the flowering phase. The largest above-ground mass is formed with a good saturation of soil moisture during the entire growing season (in agronomic terms, above 85% of the PPV, full field moisture capacity). True, the content of essential oil decreases somewhat, especially when the air temperature drops. But during the period of intensive growth, mint needs to be watered, even if the summer is not the driest. But before harvesting for 5-7 days, refrain from watering, there will be more oil in the leaves and the raw materials will be more fragrant and dry much better.
Mint is a light-loving plant. A high level of illumination has a positive effect on the yield of the above-ground mass and the content of the essential oil rich in menthol.
Mint is a culture of a temperate strip, so dry heat is contraindicated for it. The optimum growing temperature is + 18 + 20 ° C. With its increase to +23 + 25 ° C, the content of essential oil in the raw mint increases with a slight decrease in the amount of menthol. In winter, mint tolerates negative air temperatures down to -10 ° C. However, at -10 ° C at a depth of occurrence of rhizomes, they die within 24 hours. Under a layer of snow of 15-20 cm, mint tolerates an air temperature of -25 ° C.
It is interesting: In the geographical experiments of A.A.Khotin, it was found that in the southern regions, compared with the northern (average daily temperatures in July, respectively, + 23 ° С and + 18 ° С), the essential oil content of mint increased from 2 to 4%, and the menthol content fell from 55 up to 39%. When selecting a zone and a specific site, it must be borne in mind that strong winds negatively affect the quality of the crop. As a result of friction of plants, the protective shell of the glands is disrupted, which leads to a rapid evaporation of the essential oil. Losses reach 20%.