How to Grow Mint as a Medicinal Herb? A Detailed Guide to Mint Cultivation Techniques

Mint, also known as "Rendan grass," is a perennial herbaceous plant of the genus Mentha in the Lamiaceae family, distributed in various regions. It has functions such as dispersing wind-heat, clearing the head and eyes, and promoting eruption of rashes. Its tender stems and leaves can be eaten as a cold dish, clearing heat and detoxifying, with a cool and refreshing taste. It is a leafy green vegetable with good development prospects that serves both as medicine and food.

I. Botanical Characteristics

Plant height 30--80cm, the whole plant has a cool fragrance. Rhizomes are creeping and white. Above-ground stems are creeping or upright, green or purple, square, hollow, with recurved fine hairs and glandular dots. Leaves are opposite, ovate or oblong-elliptic, with fine serrations on the margins, and sparse soft hairs and yellow glandular dots on both surfaces. Verticillaster inflorescences are axillary, corolla pale reddish-purple, bilabiate. Four nutlets, ovoid. Flowering period August--October, fruiting period September--November.

II. Ecological Habits

Mint is a shallow-rooted plant, with rhizomes mostly concentrated within about 15cm of the soil surface, and horizontal distribution of about 30cm. Both rhizomes and above-ground stems have strong sprouting ability, and are used as asexual propagation material in production. Mint has strong adaptability to environmental conditions and can grow in areas below 2100m altitude. It is relatively shade-tolerant and can be intercropped with other crops, growing vigorously with excellent quality, but it prefers sunny, warm and humid environments. Rhizomes sprout and emerge at 5--6°C, the suitable temperature for plant growth is 20--30°C, and underground rhizomes can safely overwinter at -30-- -20°C.

III. Cultivation Key Points

1. Site selection and land preparation: Choose sunny, flat, fertile sandy loam with convenient drainage and irrigation for planting. Apply 4000kg of farmyard manure per mu, combined with 60kg of compound fertilizer as base fertilizer. Plow, refine, and rake level to make beds 1--1.2m wide.

2. Propagation methods: In production, rhizome propagation is mainly used, but seedling propagation can also be used. Mint is mostly cultivated in open fields; in northern regions, protected cultivation or a combination of open field and protected cultivation can be adopted. The cultivation season depends on local climate; generally, it can be cultivated in frost-free seasons. Protected cultivation can produce year-round; in northern regions, open field cultivation can be done from April--October.

Rhizome propagation: From late October to early November, dig up rhizomes from the seed reservation field, select white, thick, short-internode ones, cut into 10cm segments, and immediately plant them into pre-dug 10cm deep furrows, with row spacing 25--30cm and plant spacing 15cm. After planting, cover with fine soil, rake level and compact.

Seedling propagation: Select fields with robust plants, uniform growth, and no pests or diseases as seed reservation fields. After autumn harvest, immediately carry out one cultivation, weeding, and topdressing. In early April of the following year, when seedlings are 15cm tall, pull up seedlings for transplanting. Dig holes in the transplanting field at row spacing 20cm and plant spacing 15cm, planting 2 seedlings per hole. After planting, cover with soil and compact, then water with dilute manure water.

3. Field management: After emergence, keep the field moist and weed-free, water frequently with small amounts, and drain any accumulated water promptly. To prevent branches and leaves from shading each other, promptly guide the growth direction of above-ground and underground stems so they do not become crowded. When seedlings are about 15cm tall and after each harvest, timely topdressing is needed to promote the occurrence of new branch tips. Generally, apply 1500kg per mu of diluted human manure or urea solution. Water promptly after each fertilization.

4. Pest and disease control:

Rust disease: Harms leaves and stems, occurring frequently in rainy seasons. Control methods include strengthening field management, improving ventilation and light conditions, and spraying leaves with 25% triadimefon 1000--1500 times dilution.

Leaf spot disease (also known as white star disease): Harms leaves, occurring from May--October. At the early stage of onset, promptly remove and burn affected leaves, or spray with 75% chlorothalonil 500--700 times dilution.

Main pests include small cutworms and silver-marked noctuid moths. For small cutworms, spray the root zone with 40% fenpropathrin-malathion emulsifiable concentrate or fenpropathrin-cypermethrin emulsifiable concentrate 2000--3000 times dilution, or drench roots with 40% isofenphos-methyl 1000 times dilution. For silver-marked noctuid moths, spray with 50% chlorfluazuron emulsifiable concentrate at 30--60ml per mu mixed with water, or spray with 50% fenitrothion 1000 times dilution.

IV. Harvesting

In areas with suitable conditions, planting once can allow continuous harvest for 2--3 years. Generally, when the main stem is about 20cm tall, tender stems and leaves can be harvested for consumption. In southern regions, harvesting can be done year-round, with the highest yield and best quality from April--August when the climate is suitable, with harvest intervals of 15--20 days; in northern regions, protected facility cultivation in winter can also achieve year-round supply.

For medicinal use, harvesting is usually done twice during the growing period. The first (first cutting) is 5--6 days before the Minor Heat solar term, when leaves are at their most luxuriant and flowers have not yet opened, cutting the above-ground parts; the second is between the Autumn Equinox and Cold Dew, when flowers are in full bloom and leaves have not yet fallen. The second harvest is preferred for medicinal use.

V. Seed Reservation Techniques

Mint is prone to degeneration, so seed reservation and selection work should be done well. Common methods include:

1. Plot selection for seed reservation. For fields with only a small amount of mixed or degenerated plants, in late April when seedlings are 15cm tall, or in late August when the second-cutting mint is 15cm tall, combine with weeding and pull out wild species or other mixed species with roots in 2 rounds, while also removing inferior and diseased seedlings for seed reservation.

2. Re-planting for seed reservation. In late April, select robust and non-degenerated plants in the field, transplant them to the seed reservation field at row spacing 15cm x plant spacing 20cm, strengthen management, cultivate until early winter then dig up, obtaining 70%--80% white new rhizomes for seed use.