Licorice root

[Production area distribution]

Licorice: mainly produced in Inner Mongolia, Gansu, and **. Also produced in Northeast China, Hebei, Shanxi and other places.

Glycyrrhiza inflata and Glycyrrhiza glabra: mainly produced in ** and Gansu.

[Medicinal material characteristics]

Licorice: the root is cylindrical, 25-100cm long, 0.6-3.5cm in diameter. The surface is reddish-brown or grayish-brown, with prominent longitudinal wrinkles, furrows, lenticels and sparse fine root scars. The texture is solid, the fracture is slightly fibrous, yellow-white, powdery, the cambium ring is obvious, the rays are radial, and some have fissures. The surface of the rhizome has bud scars, and the middle of the fracture has pith. The odor is slight, with a distinctive sweet licorice taste.

Glycyrrhiza inflata: the root and rhizome are woody and thick, some are branched, the outer bark is rough, mostly grayish-brown or grayish-brown. The texture is hard, with much wood fiber and little powderiness. The rhizome has many and thick adventitious buds.

Glycyrrhiza glabra: the root and rhizome are relatively solid in texture, some are branched, the outer bark is not rough, mostly grayish-brown, and the lenticels are fine and inconspicuous.

Overview of the resource distribution and application of licorice in China

I. Overview Licorice, also known as sweet grass root, red licorice, and powdered licorice. It is the leguminous plant Glycyrrhiza uralensis Fisch., with the root and rhizome used as medicine. It has the effects of clearing heat and detoxifying, moistening the lungs and relieving cough, and harmonizing various medicines; processed licorice has the effect of tonifying the spleen and replenishing qi.

II. Plant characteristics A perennial herb, 30-40 cm tall, with a thick, cylindrical root, sweet in taste, and a brownish-red outer bark. The stem is upright, slightly woody at the lower part. Leaves are alternate; odd-pinnate compound leaves, with 7-17 leaflets, ovate-elliptic, covered on both sides with glands and short hairs. Racemes are axillary, flowers papilionaceous, pale purplish-red. The pod is oblong, sometimes sickle-shaped or curved into a ring, densely covered with brown stinging-hair-like glandular hairs. Seeds are flat and round. Flowering period is June-July, fruiting period is July-September.

III. Growth habits

Licorice mostly grows in the north temperate zone, in plains, mountainous areas or river valleys at an altitude of 0-200 m. Wild licorice is accompanied by plants such as Apocynum venetum, Populus euphratica, reed, sand sagebrush and ephedra. The soil is mostly sandy soil. The soil pH is best neutral or slightly alkaline, and it grows poorly in acidic soil. Licorice prefers an ecological environment with sufficient sunlight, relatively low rainfall, hot summers, severe cold winters, and large temperature differences between day and night, and has the characteristics of being light-loving, drought-tolerant, heat-tolerant, salt-alkali-tolerant and cold-tolerant. Four-year-old cultivated licorice is set as the best harvesting period, which is more suitable.

Northwest, North China and Northeast China are all suitable for planting licorice, especially Inner Mongolia and **.

IV. Cultivation management

(1) Site selection and land preparation

Usually choose fertile soil, loose texture, good drainage, and low salinity-alkalinity sandy soil. Waterlogged lowlands and areas with high groundwater levels are not suitable for planting. Generally, deep plowing is about 20 cm, and after plowing, level and harrow finely. If ridge cultivation is used, the ridge spacing is generally 60-70 cm.

Areas with heavy clay soil and acidic tendency are not suitable for planting licorice.

(2) Propagation methods

1. Seed propagation

(1) Seed treatment

① Physical method: coarse sand or a rice milling machine can be used to abrade the seed coat, making the seed coat rough and increasing water permeability; or before sowing, soak the seeds in warm water at 45°C for 10 hours.

② Chemical method: mix seeds with concentrated sulfuric acid at a ratio of 1 part concentrated sulfuric acid to 1.5 parts seeds, mix evenly, then rinse with clean water, and sow after drying.

(2) Direct sowing of licorice

As a perennial herb, licorice can be sown in spring, summer or autumn, but according to surveys of several licorice planting bases in China, the yield and quality are better with spring sowing, so it is recommended to sow in spring as much as possible.

Mechanical or manual sowing can be used, with drilling, sowing depth 2-3 cm, and appropriate compaction after sowing. The sowing rate for direct sowing should be determined according to the growth period of licorice: if harvested in 2 years, the sowing density should be relatively large, generally about 4 kg per mu; if harvested in 3-4 years, the sowing density should not be too large, generally 1-1.5 kg per mu.

(3) Seedling raising and transplanting

Around mid-April, sow when the daily average temperature is stable above 5°C. Mechanical or manual sowing can be used, with drilling, sowing depth 2-3 cm, row spacing 30 cm. Compact appropriately after sowing. The sowing rate is about 12 kg per mu.

Seedling raising and transplanting are generally carried out in the spring of the second year. When transplanting, open a furrow, place the licorice obliquely (at a 45° angle) into the furrow, then cover with soil and compact. This is conducive to the growth and development of the root and rhizome and facilitates harvesting.

(4) Comparison of the two sowing methods for licorice:

Taking 2-year-old licorice as an example, direct sowing uses a large amount of seed, and because licorice is a deep-rooted plant, its growth is uneven, which not only affects commodity quality but also brings inconvenience to harvesting. For seedling raising and transplanting, the sowing rate is generally about 12 kg, and one mu of seedlings can be transplanted to more than 10 mu. Seedling raising and transplanting not only saves seed usage, but the plants grow robustly, the root and rhizome grow neatly, harvesting is convenient, and the commodity quality is good and the yield is high. Therefore, for planting licorice, the seedling raising and transplanting method is better.

2. Rhizome propagation

Adventitious buds on the licorice rhizome can sprout new plants. Select rhizomes 0.5-1.5 cm thick, cut them into 15-25 cm segments, and each segment should have 3-5 adventitious buds. The method is mostly strip planting or hole planting, with row spacing 50-60 cm, plant spacing 25 cm, and depth 15 cm; for salinized wasteland and dry plots, the depth can reach 20 cm. Compact appropriately after planting. The planting period is mostly spring or autumn, with early April in spring and late October in autumn being suitable.

(3) Field management of licorice

1. Thinning to a stand The number of retained seedlings per mu of licorice is generally about 12,000-15,000 plants. If the sowing row spacing is 30 cm, then the plant spacing during thinning can be maintained at 18.5-20 cm.

2. Irrigation

Before and after emergence, licorice should be kept with moist soil frequently to facilitate emergence and seedling growth. Specific irrigation should depend on soil type and salinity-alkalinity: for sandy soil with no salinity-alkalinity or slight salinity-alkalinity, water can be applied immediately after sowing; for heavy clay soil or soil with relatively heavy salinity-alkalinity, water should be applied before sowing, sowing should be done to seize moisture, and no water should be applied after sowing, so as to avoid soil compaction and a rise in salinity-alkalinity. The key to cultivating licorice is preserving seedlings; generally, after the plants have grown, no further watering is needed.

3. Intertillage and weeding

Intertillage and weeding are generally carried out in the same year as emergence, especially during the seedling stage, when weeds must be removed in time. From the second year onward, licorice roots begin to tiller, and weeds find it difficult to compete with them, so intertillage and weeding are no longer needed.

4. Fertilization

Before sowing, sufficient base fertilizer should be applied, preferably barnyard manure. In the sowing year, phosphate fertilizer can be applied as a top dressing in early spring, and before freezing in winter, 2000-2500 kg of organic fertilizer can be applied per mu as a top dressing. Licorice roots have root nodules and have nitrogen-fixing ability, so nitrogen fertilizer is generally not applied.

5. Pests and diseases and their control

In rainy seasons, powdery mildew and rust are likely to occur, and Bordeaux mixture at 1:1:150 can be sprayed; in dry seasons, red spiders are likely to occur, and 40% dimethoate emulsifiable concentrate at 1000-1500 times dilution can be sprayed for control. Among underground pests, cutworms bite the root and rhizome, and 0.5 kg of 90% trichlorfon technical material plus 50 kg of bait can be mixed into poisoned bait to trap and kill them.

V. Harvesting and processing

Seed propagation takes 3-4 years, and rhizome propagation takes 2-3 years before harvesting. Harvest in autumn from late September to early October, when the aboveground stems and leaves wither. Licorice roots are deep, so deep digging is necessary; do not break them or damage the root bark. After digging out, remove the residual stems and soil; do not wash with water. While fresh, separate the main root and lateral roots, remove the reed head, fibrous roots and branch forks, sun-dry until half dry, tie into small bundles, and then sun-dry until completely dry; it can also be harvested in spring before the licorice stems and leaves emerge, but the quality from autumn harvesting is better.