How to Grow Codonopsis for High Yield? A Detailed Guide to Standardized Cultivation Techniques

Codonopsis (Codonopsis pilosula (Franch.) Nannf.) is a perennial herbaceous plant of the Campanulaceae family, using its root as medicine, and is one of the major commonly used Chinese medicinal materials. Codonopsis is neutral in nature and sweet in taste, with the effects of tonifying the middle and replenishing qi, strengthening the stomach and promoting fluid production. It is used for symptoms such as weakness of the spleen and lungs, shortness of breath and palpitations, poor appetite and loose stools, deficient wheezing and cough, and internal heat with wasting-thirst. Modern pharmacological studies show that Codonopsis has various effects such as regulating blood sugar, promoting hematopoietic function, lowering blood pressure, resisting hypoxia, enduring fatigue, enhancing body immunity, regulating gastric contraction and resisting ulcers. Codonopsis has a long history of medicinal use and a wide distribution of resources, mainly distributed in North China, Northeast China and Northwest China. At present, the largest-scale commercial Codonopsis is the “Baitiao Dangshen” from Gansu; in addition, the one produced in Shanxi is called “Lu Dangshen”, and the one produced in Northeast China is called “Dong Dangshen”. The Codonopsis species included in the pharmacopoeia also include Codonopsis pilosula var. modesta and Codonopsis tangshen. Codonopsis pilosula var. modesta is mainly produced in Wen County, Gansu and Jiuzhai County, Sichuan, and the medicinal material is called “Wen Dangshen”. The ecological conditions in the distribution areas of Codonopsis differ markedly, the planting methods each have their own characteristics, and the quality varies greatly, but the most famous are Gansu Baitiao Dangshen, Shanxi Lu Dangshen and Tai Dangshen, Gansu Wen Dangshen, and Chuan Dangshen. In order to standardize the production of Codonopsis medicinal material, ensure the quality of the medicinal material, and increase yield, standardized cultivation of Codonopsis must be promoted.

I. Requirements of Codonopsis for Environmental Conditions

Codonopsis has strong adaptability, prefers a mild, cool and humid climate, has relatively strict requirements for light, is drought-tolerant, and is relatively cold-tolerant. At each growth stage, its temperature requirements differ. When the temperature is 3°C to 7°C, sprouting begins; at 10°C to 8°C, seedlings emerge; when the daily average temperature is 18°C to 20°C, the plants grow fastest. The most suitable vernalization temperature is 0°C to 5°C. Generally, it can grow normally between 8°C and 30°C, and when the temperature is above 30°C, the growth of Codonopsis is inhibited. Codonopsis has relatively strong cold resistance; its roots overwinter in the soil and will not be frozen to death even under severe cold conditions of about minus 25°C, and can still maintain vitality. If high temperatures and hot weather persist during the growth period, the aboveground parts are prone to withering and disease. Codonopsis is a deep-rooted plant. The soil pH should preferably be 6.5 to 7.0. Neutral, slightly acidic, loose-textured, deep, fertile, well-drained soil rich in humus should be selected to facilitate full development of the Codonopsis root system. The water requirements of Codonopsis vary with the growth stage. The sowing period and seedling stage require more water; when water is insufficient, it is not easy for seedlings to emerge, and after emergence they are also prone to drying out and dying. After transplanting, the water requirements are not strict, but it should not be overly humid. Generally, normal growth can occur under conditions of annual precipitation of 400 to 1200 mm and an average relative humidity of about 70%. Codonopsis has relatively strict light requirements: seedlings prefer shade, while mature plants prefer sunlight. The seedling stage avoids sun exposure, and seedling cultivation mostly selects shaded locations. The transplanting site should be chosen in a place with sufficient sunlight. Codonopsis avoids continuous cropping, and generally should be planted again after an interval of 3 to 4 years; the previous crop is preferably legumes or grasses. Codonopsis seeds are very small, and the suitable soil moisture content for seed germination is 13% to 20%; the minimum soil temperature for seed germination is 5°C, 15°C to 20°C is the optimum temperature, and above 30°C is unfavorable for seedling emergence. The germination rate of seeds treated with boric acid is 75%, while the control is only 16.6%. This is because weak acid can replace the light effect. In production, Codonopsis sowing should not be too deep, and the soil covering should not be too thick, so as to meet the seeds' demand for light during germination.

II. Seedling Raising Techniques

1. Seed collection

Select a Codonopsis field with robust growth, thick and large roots, and no pests or diseases as the seed collection field, and collect seeds from Codonopsis that is more than two years old. The harvesting period is about early to mid-October. When the fruits turn yellow-brown and soft, and the seeds are black-brown, this indicates that they are already mature and can be harvested. The most commonly used collection method is as follows: after the aboveground vines of Codonopsis are killed and turn yellow by frost, and the nutrients in the stems have been transported to the underground roots, when the stems have little sap and become dry, use some simple manual tools such as a sickle to cut off the vines, handling them carefully and gently to reduce seed shattering, transport them back to the threshing site, and place them in the sun to dry for 7 to 10 days. After drying, some capsules split open, and threshing can then be carried out.

2. Threshing and drying

Thresh during the period from the end of October to November 20 on fine weather days. The threshing method is: on canvas or another hardened ground surface, spread the Codonopsis vines into a thin layer of 20 to 30 cm, gently beat them with a wooden stick or similar tool to shake open the capsules and let the seeds pop out, and use a wooden fork to shake off the vines. After threshing, clean by sample sieve or winnowing to remove mixed impurities, empty and shriveled seeds, and dust. During the operation, care should be taken to avoid damaging the seeds as much as possible; damaged seeds have poor germination ability.

After threshing and cleaning, Codonopsis seeds should be further dried to the standard moisture content of the seeds. The standard moisture content of Codonopsis seeds is 11.5% to 13.0%, with an average of 12%. The drying method is shade drying. The method is, under low-temperature winter conditions, to place the seeds on canvas in a ventilated place to air-dry, spread into a thin layer of 3 to 5 cm, turning them frequently, or put them into cotton cloth bags and hang them under a dry and ventilated cool shed to dry; they must not be exposed to high temperature or dried quickly in a short time.

3. Storage of Codonopsis seeds

Codonopsis seeds are small, contain very little energy, and do not store well. After storage at room temperature for 1 year, the germination rate drops to about 25%; after storage at room temperature for 2 years, the germination rate drops to 3.7%. Therefore, seeds from the previous year are not suitable for use as seed. Storage in a refrigerator (0°C to 5°C) can prolong seed life. Therefore, during the storage period of Codonopsis seeds, the temperature should be controlled as much as possible under low-temperature conditions of 0°C to 5°C. If the seeds are exposed to smoke or come into contact with table salt during storage, they will lose their germination rate. During storage of Codonopsis seeds, the moisture content must be below 13%, otherwise they will heat up through respiration and lose germination ability. Codonopsis seeds should be stored in cotton cloth bags or paper bags, and must not be stored in ordinary plastic bags. During storage, pay attention to preventing insects and moisture, do not expose them to strong light, and do not place them in places with heat sources, such as near radiators, stoves or heated brick beds.

4. Land preparation and fertilization

(1) Land preparation. Codonopsis seedlings are afraid of sun exposure, so the seedling bed should be selected on a moist shaded slope. Choose sandy loam land that is flat in terrain, loose and fertile in texture, with good soil moisture, no water accumulation, few weeds, rich in humus, and with relatively light damage from underground pests. Deep plow 25 to 30 cm, break up clods, remove grass roots, branches and stones, and rake level. When necessary, autumn plowing for freeze-thaw can be carried out. If drainage is poor, beds should preferably be made: bed surface width 100 cm, bed spacing 25 to 30 cm, bed height 15 to 20 cm, bed length variable, with the direction of bed length the same as the slope direction. If the land is dry, irrigate first, and sow after the water infiltrates the surface soil and the soil becomes loose.

(2) Fertilization. The fertilization of Codonopsis throughout its life can be divided into four types: base fertilizer, seed fertilizer, topdressing and foliar fertilizer. Organic fertilizer must be fully decomposed and meet harmless sanitation standards, and foliar fertilizer must meet GAP requirements.