Scientific name of Japanese mint is Mentha arvensis var. piperascens. It is also known as American wild mint, and Chinese mint. It is a vigorously growing, branched, hardy perennial plant which reaches up to a height of 1 meter upon maturity. Violet tinged quadrangular stems bear broadly ovate leaves; lilac-coloured flowers are borne in axillary and terminal flowering spikes.
Growing practices for Japanese mint is similar to that of peppermint. A detailed account of various growing practices for Japanese mint plants is given below:
Climate – A cool, temperate and sub-temperate climate with a day temperature of 20 to 25°C is the most ideal temperature requirement. As far as rainfall is considered, a light rainfall favors vigorous growth of mint plants. Mint grows up to an altitude of 1,000 meters in temperate and subtropical regions. Generally speaking, wet climate and moist soils are the most ideal environmental conditions for growing almost all mint species.
Soil – Well-drained, rich sandy-loam to clay-loam soils with soil pH of 6–7 are the most ideal soils for growing these plants. Clayey soils, high pH and frost are unsuitable.
Light – It is a long day plant, hence prefers sunny locations; partial shade is preferred at times, but full shade is undesirable.
Propagation – Propagation is by planting divided rhizomes (stolons or runners). Generally 8 to 10 cm long stolons with 2–4 growing points are used for propagation; suckers and herbaceous stem cuttings may also be used as propagation materials.
Planting Density – Approximately 250 kg/ha of fresh, healthy and succulent planting materials such as stolons or rhizomes or runners or cuttings are needed.
Pre-treatment – Planting Materials should be treated with a recommended fungicide before planting them in the main field
Spacing – Ideal spacing is 40 cm between two rows and 10 cm between two plants
Planting Time – Mint can be planted any time of the year. However early spring is the best. Planting is done when soil temperature is low, i.e. approx.@20°C
Planting Depth – 0.5 cm – 1 cm deep in furrows
Field Preparation – The land is repeatedly ploughed twice or thrice; levelled and made free of all weeds before planting
Establishing Planting Materials – Cuttings or planting materials get established within 10 days
Manure and Fertilizers Application – In commercial cultivation practices, FYM (farm yard manure) or compost or vermicompost @ 15 – 30 tons/hectare along with NPK @ 40, 60 and 40 kg /hectare is mixed with the top soil at the time of land preparation; In Zinc-deficient soils, 20 kg of ZnSO should be mixed in the soil in order to avoid Zn deficiency. Nitrogen@80 Kg/hectare is also given as top dressing in 2 doses; first dose is 40 days after plants get established and second dose is after the appearance of the first flush.
Method of Fertilizer Application – Broadcasting in rows
Irrigation – Mint is a shallow-feeder with shallow root system and hence deep water table with good drainage is recommended. In other words, mint is a moisture-loving plant and needs lots of moisture for its healthy growth. The crop needs 6–9 irrigations during dry season and 2–3 irrigations after rains.
Weed Control – Three weeding are required in total; each before every harvest; manual weed control is recommended
Disease-Pest Management – There is no severe insect-pest damage or disease incidence observed in mint plantation. Sometimes, mints are susceptible to whitefly and aphids. They can be controlled by spraying any of the recommended bioinsecticides such as neem emulsion or tobacco solution or soap solution.
Harvesting – Mint leaves may be harvested at any time for culinary purposes. For oil extraction, crop maturity needs to be determined by distillation of leaf sample in Clevenger’s apparatus. If the average oil content in leaves is found to be around 0.5%, the crop is ready for harvesting. Generally speaking, mint crop for oil extraction is harvested at flowering stage. Harvesting during dry sunny days is recommended. 2-3 harvests in a year may be done. First harvest stage is reached in 105–110 days of planting. Subsequent harvests may be done at an interval of 80–90 days. During harvesting, fresh herbage is cut 10 cm above the ground using a sharp knife. Harvesting on cloudy or rainy day should be avoided as it decreases menthol content present in leaves.
Days to Maturity – 240 days to complete a full growth cycle
Yield – Yield form commercial plantations: 15-20 tons fresh herbage/acre/annum in 2 harvests
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