Detailed Explanation of Artificial Cultivation Techniques for the Chinese Medicinal Herb Liao Asarum

Asarum grown in the Tieling area is called Liao Asarum, a Chinese medicinal herb native to the Changbai Mountains. It mainly contains essential oils, asarone, palmitic acid, asarum alkaloids, methyl eugenol, and other components. The whole plant can be used as medicine; it is an effective remedy for dispelling wind-cold and promoting water metabolism, and has analgesic, sedative, diaphoretic, and expectorant effects. It is also used to extract insect repellents.

1 Biological Characteristics

Asarum seeds have a short lifespan. After sowing, germinated seeds can quickly take root, but they do not emerge from the soil that year; they wait until the spring of the 2nd year to sprout. In naturally matured seeds, the embryo is not yet fully mature and requires 45-60 days of after-ripening in soil or sandy soil with a moisture content of 30%-70% before they can germinate. Asarum is a shade-loving plant and fears direct sunlight at midday in summer; when cultivated on flat land, Asarum must be shaded. However, excessive shading is also detrimental to its growth. According to observations, before May 20 (Xiaoman), no shading is needed; after late May, shading must be provided. Asarum grows well in slightly acidic or neutral soil with high humus content; it requires moist, loose soil and good drainage conditions.

2 Cultivation Techniques

2.1 Land Preparation. For artificial cultivation of Asarum, choose a plot in front of or behind the house, or one with fertile soil, high organic matter content, no water accumulation, and convenient management and guarding, because Asarum has a relatively long life cycle; from planting to harvest and sale of large goods takes at least 5 years. Therefore, both the Asarum and the materials must be managed, and a fence or courtyard wall must be built to prevent damage from natural causes and from humans and livestock.

2.2 Land Preparation, Fertilization, and Bed Making. After the Asarum plot is selected, land preparation, fertilization, and bed making must be carried out before planting. First remove the roots and stubble of the previous crop, apply 2000 kg of decomposed high-quality manure per mu, spread it evenly, then deep plow 20 cm, and make beds 1.2 m wide. The bed length is 15-20 m or depends on the terrain, with a 30 cm wide walkway ditch left between beds.

2.3 Seedling Raising. The sowing bed is made in the same way as the planting bed. Sowing methods include drilling and broadcasting. For broadcasting, sow 150 g per square meter, cover with 1 cm of sieved humus soil, then scatter a layer of dry leaves or thinly spread a layer of rice straw on top to keep the seedbed moist. For drilling, open furrows at horizontal intervals of about 10 cm, with a furrow depth of 2-3 cm, sow 75-100 g per square meter, cover with 1-1.5 cm of soil, and also cover with dead leaves or rice straw on top. In the spring of the 2nd year after sowing, Asarum begins to emerge. Shading must be carried out from the start of emergence, and hoeing and loosening the soil must be done frequently. By the autumn of the 3rd year, planting can be carried out.

2.4 Planting

2.4.1 Planting Time. Planting can be done in both spring and autumn. In spring, carry it out in mid-to-late April when the buds have not yet sprouted. In autumn, carry it out from late September to early October.

2.4.2 Planting Density. After the planting bed is prepared, plant at a spacing of 20 cm x 20 cm. To harvest one year earlier, when seedlings are sufficient, the density can be increased and planting can be done at a spacing of 20 cm x 10 cm. Dig furrows 10 cm deep and plant 2-3 plants per hole. When planting, spread the root system out, lift the seedling upright, and place the rhizome head (bud) at a position 3 cm below the soil surface, press firmly, then water. After the water settles, cultivate soil and close the hole. Then, scatter a layer of half-decomposed fallen branches and leaves or chopped rice straw between the plants and rows to prevent heavy rain from washing away the bed surface and to prevent sun-induced hardening.

2.4.3 Planting. When planting during the growing season, place rice straw under the leaves after planting to prevent the leaves from being scorched by high temperatures on the soil surface, which would cause the leaves to dry up and rot. Planting, watering, and shading must be done together to prevent the leaves from drying up and to shorten the recovery period. Once Asarum seedling leaves dry up, new leaves cannot develop that year, which will cause the entire plant to die from failure to produce leaves, resulting in missing plants and broken rows.

2.5 Field Management

2.5.1 Building Shade Structures. At present, there are 2 shading methods. One is to build a frame with wooden poles and cover it with corn stalks. The frame is the same width and length as the bed surface and 80 cm high. The other is to use steel wire or bamboo strips to make arched frames at 2 m intervals and cover them with black plastic shade netting. The light transmittance of the shade netting and corn stalks must be adjusted according to the season and the age of the Asarum seedlings. In the 1st-2nd years after planting, the seedlings are small and the canopy density is poor, so a light transmittance of 40% is appropriate. After 3 years of planting, the seedlings are older and the canopy density is high, so the light transmittance should be appropriately higher, with 50% being suitable. To increase exposure to scattered light in the morning and evening, when using plastic shade netting, leave 20-30 cm uncovered at the bottom corners.

2.5.2 Fertilization and Irrigation. Asarum is a perennial herbaceous plant that grows very slowly. It takes 4-5 years after transplanting before there can be a harvest. To make Asarum grow quickly and achieve high yield, sufficient base fertilizer must be applied, and each year before freezing, topdressing manure should be applied over the surface. Irrigation should be carried out during dry weather.

2.5.3 Loosening Soil, Hoeing, and Hilling. During the growth process of Asarum, soil should be loosened and weeds hoed 3-4 times each year. After irrigation, loosen the soil promptly to prevent the bed surface from cracking. While loosening the soil and hoeing, the beds should also be leveled and soil hilled up.

2.5.4 Overwintering Management. In autumn before freezing, after Asarum leaves have dried up, the shade netting can be removed. Combined with autumn fertilization, apply 1-2 cm of surface-covering manure and hill up soil for cold protection.

2.5.5 Seed Harvesting and Storage. After planting, Asarum begins to flower and bear fruit in the 3rd year, and seeds can be harvested. Asarum seeds mature in early June, and the mature fruits split open naturally, causing the seeds to fall to the ground. Harvest in stages when the fruit skin changes from green to white and the fruit flesh is powdery, that is, when the fruit feels slightly soft when pinched by hand and is about to split but the seeds have not yet fallen off. After harvesting, rub off the seed coat and wash out the seeds with clean water, and they can then be sown. If sowing cannot be done temporarily, mix the seeds evenly with 5 times their volume of fine sand, maintain 30%-50% moisture, and sow after 45 days of after-ripening.

3 Harvesting and Processing

Asarum can be harvested 4-5 years after planting. Harvesting is generally carried out during the peak growth period from late July to mid-August. When harvesting, dig out the whole Asarum plant with a pickaxe, shake off the soil, and do not wash with water so as to preserve the aroma of the roots. Dry it by heating or place it in a ventilated, cool place to air-dry, and it can then be stored in the warehouse or @#@136@#@.

4 Precautions

4.1 The spacing between the arched frames for the shade netting must not exceed 2 m, and they must be fixed into a tunnel shape to prevent strong winds from damaging the shade netting and causing it to lose its shading function.

4.2 In the early stage of planting, when Asarum seedlings are relatively small, weeds in the field must be removed promptly to prevent the seedlings from being overwhelmed.