Study on Planting and Cultivation Techniques of Polygonatum

Lingyu DENG　Piaoling HUANG　Si LIN　Fengfeng XIE　Hua ZHU

AbstractPolygonatum is a food having the concomitant function of both medicine and foodstuff. It is relatively common in the tonic medicinal material market and is a common bulk medicinal material in China. Because of its good medicinal value and health care value， its artificial cultivation has become a hot topic， in order to increase market demand. The cultivation techniques of Polygonatum were discussed and analyzed by collecting and consulting data， as well as practical investigation.

Key wordsPolygonatum; Cultivation; Pests and diseases

Polygonatum， also known as Longxian， Yexianjiang， Shandaojiu and Laohujiang， belongs to liliaceae. Polygonati Rhizoma has three sources， i.e.， dried rhizomes of Polygonatum kingianum Coll. et Hemsl.， Polygonatum sibiricum Red. and Polygonatum cyrtonema Hua[1]. Polygonati Rhizoma is sweet and neutral in nature， attributive to the spleen， lung and kidney meridians， and has the effects of tonifying qi and nourishing yin， invigorating the spleen， moistening the lung， and nourishing the kidney. Polygonati Rhizoma is used for qi deficiency of the spleen and stomach，   weakness， lack of stomach yin， dry mouth and reduced appetite， cough caused by dryness， lack of essence and blood， soreness and weakness of waist and knees， premature graying of beard and hair， and consumptive thirst[2]. In 2002， it was included in the catalogue of medicinal and edible homologous foods， integrating medicinal， edible and ornamental purposes. In recent years， as people pay more and more attention to health， health preservation and health care， the market demand of Polygonati Rhizoma is increasing day by day， and wild resources can no longer meet the market demand. Artificial cultivation is an effective method to fill the market demand.

Biological Characteristic

Polygonatum has cylindrical rhizomes， 1-2 cm in diameter. Its stems are 50-90 cm high， or up to 1 m or more， sometimes climbing. The leaves are in verticillate， 4-6 per round， striplanceolate， 8-15 cm long， 6-16 mm wide， and the apex is rolled or curved into a hook （Fig. 1）. The inflorescence usually has 2-4 flowers， and is shaped like an umbrella. The berries are black， and have 4-7 seeds each. The flowering period is May-June， and the fruiting period is August-September[3].

Growth and development

The growth process of Polygonatum plants can be divided into four stages： seedling stage， vegetative growth stage， reproductive growth stage and overwintering stage （withering of the aboveground part）.

Ecological habits

Polygonatum is resistant to cold， drought and shade， and afraid of waterlogging. It prefers moist， fertile， and deep soil. It is mainly distributed in barren hillsides， under shrubs， and at forest edges， valleys and roadsides. When planting Polygonatum， we should choose a place that is moist or hidden but the upper layer has sufficient light transmittance.

Cultivation techniques

Site selection

Because Polygonatum is afraid of waterlogging， and prefers moist， fertile and deep soil， so the sites selected often have smooth drainage， and loose and fertile flat soil or sandy soil with canopy closure value <0.5 and slope value <15° and rich in humus， or sparse woodland that is not easy to accumulate water[4].

Land preparation

All kinds of weeds on the land to be planted are cleared， and the fields are deeply ploughed more than 30-40 cm use a cultivator or a small groundstriking machine while breaking large pieces of soil into small pieces. Fully fermented farmhouse organic fertilizer and compound fertilizer are evenly spread on the surface of the newly cultivated soil at the rates of 75 t and 1 500 kg per hectare， respectively. Furrows are dug with a depth of 40 cm at intervals of 1.6 m， and the borders formed have a width of 1.2 m and a height of 30 cm. The soil surface is covered with organic fertilizer. The soil surface with organic fertilizer is covered. Then， the borders are covered with 1.5 m wide airpermeable mulch， and the edges of the film are pressed with soil to avoid wind blowing and detachment.

Propagation method

The propagation method of Polygonatum mainly adopts rhizome propagation， and it can also be propagated by seeds.

Propagation using rhizomesNi et al.[5] showed that in the matrix peat soil∶perlite=3∶1， the growth effect of Polygonatum was the best. Every year in late March or early October， the rhizomes of Polygonatum are planed out， and the young part of the apex is cut into several sections， each of which has 2-3 nodes， and the rhizome length is 8-12 cm. When the wound is slightly dry， they are planted into prepared borders. According to the requirements of two rows per border and the plant spacing of 40 cm， the rhizomes are planted with holes on the breathable film， and the soil is watered thoroughly after planting is completed. For planting in late autumn， the soil is covered with some livestock manure， manure or straw before freezing to keep warm over the winter. After thawing in the following year and before emergence， the manure blocks should be broken and leveled or the straw should be removed to keep the soil moist， which is conducive to the emergence of plantlets.

Seed propagationTwoyearold plants with robust growth and no pests and diseases are selected， and phosphorus and potassium fertilizers are applied in summer to promote plant growth， maturity， robustness and full grains. The fruit is collected in August when the berries have turned black and ripe， and subjected immediately to wet sand stratification. Specifically， 1 part of seeds and 3 parts of wet sand （the humidity of the sand is controlled according the standard that it can be held with hands into a ball， without dripping water between the fingers， and loose when you let go） are prepared. Then， a 33 cm deep pit is dug in the shade， and the fruit is buried after laying an isolation layer. The soil is kept moist to prevent water accumulation， and it is taken out in late March of the following year to sieve out the seeds， which are sown into prepared borders. For seedling cultivation， shallow trenches can be opened according to the row spacing of 13-17 cm， and the seeds are evenly sown into the trenches， covered with 1.5 cm of soil， which is slightly pressed， watered， and covered with a layer of straw to keep moisture. The straw is removed before emergence. The seedlings should be properly thinned in dense places， and transplanted after 1 year.

Water and Fertilizer Management

Water management

After planting， the plants are watered. Watering is performed in time according to soil humidity in the field period to keep the soil moist. In the rainy season， the ditches are cleared to ensure smooth drainage， and avoid water in the bed.

Weeding

In the early stage of planting， weeds grow relatively fast. After about half a year， the branches and leaves of Polygonatum grow more， and the growth of weeds slows down. For weeding during intertillage， the application of chemical herbicides should be avoided. In the first year after planting， shallow cultivating should be carried out in combination with artificial weeding according to the growth of Polygonatum. In the second year after planting， deep cultivating should be combined with weeding， soil cultivation， and fertilization to increase the thickness of the root soil layer， which is conducive to the expansion and growth of Polygonatum rhizomes. The damage to the roots of Polygonatum should be avoided， which is not conducive to its growth.

Nutrient management

Fertilizers are mainly organic fertilizers， supplemented by compound fertilizers and various trace element fertilizers. Organic fertilizers include fully decomposed farmyard manure， plant ash， crop straw， etc. No fertilizer is applied in the first year after planting， and compound fertilizer is applied twice a year from the second year， 100 kg per mu each time. The plants should be watered once after each fertilization. During the period of vigorous growth （July to August）， 0.2% potassium dihydrogen phosphate can be sprayed， once every 15 d， for a total of 3 times， to promote plant growth. Sunny dry plots should be watered in time. Polygonatum is afraid of water and prefers shade. Attention should be paid to drainage and intercropping with other crops.

Disease and Pest Control

Diseases

The main diseases include leaf spot and black spot， both of which damage leaves and affect plant growth. Pests： There are mainly aphids， blackcutworms and grubs， all of which can bite off the seedlings， eat new leaves and shoots， and endanger the normal growth of Polygonatum[6].

Control methods

Leaf spot disease： It is the main disease of Polygonatum， which is caused by the fungus Cladosporium sp. It harms the leaves. First， irregular yellowbrown spots appear from the tip of the leaves， gradually spread downward， and become more serious in the rainy season， until the leaves turn yellow. Prevention and control measures： The plantations are cleared when harvesting， and the diseased bodies are eliminated. Before the onset and at the beginning of the onset， 1∶1∶100 Bordeaux mixture or 1 000 times dilution of 50% tuzet wettable powder are sprayed once every 7-10 d， continuously several times.

Grubs： They damage seedlings and rhizomes. Control methods： The manure applied should be fully decomposed， preferably at a high temperature; and adult pests can be trapped and killed by light; and 3% phoxim and 15% lorsban can be applied to control the pests together in the planting area of Polygonatum.

Blackcutworms： In the planting area of Polygonatum， 15% lorsban mixed with sand can be used， which can greatly reduce the harm of blackcutworms; or 48% lorsban spray can be adopted.

Cotton bollworms： They belong to noctuidae of Lepidoptera， and their larvae damage buds， flowers and fruit. Control method： Black light can be used to trap and kill adults. 2.5% deltamethrin EC 2 000 times dilution or 20% cypermethrin EC 2 000 times dilution or 50% phoxim EC 1 500 times dilution is sprayed when the larvae are in full bloom. Biological control can also be carried out by using natural enemies such as Exorista japonica and Charops bicolor.

Aphids： They damage leaves and seedlings. Control method： 50% dimethoate EC 1 000-2 000 times dilution or dimethoate EC 1 500-2 000 times dilution is sprayed.

Processing

Harvesting

It can be harvested in 3 to 4 years for seed propagation and 1 to 2 years for rhizome propagation. Generally， it can be harvested in autumn and spring. The rhizomes harvested in late autumn and early winter are plump and have the best quality. The aboveground parts， fibrous roots and rotten scars are removed， and the sediment is washed off.

Processing of Polygonatum rhizomes

Processing by steamingPolygonatum rhizomes are cut into small pieces， which are washed and placed in a beaker， soaked in a small amount of water for 6 h. Half of it is steamed under normal pressure with water for 3 h， dried to semidry， steamed for 3 h， dried to semidry， and so on repeatedly until the taste is not irritating. The other half is steamed with high pressure and water for 3 h， dried to semidry， steamed for 3 h， dried to semidry， and so on repeatedly until the taste is not irritating.

Processing with wineRaw Polygonatum rhizomes， after cleaning and drying， are added with 20% yellow rice wine， and they are mixed well. After the rice wine fully infiltrates Polygonatum rhizomes， they are usually stood for 5 h. Then， the soaked Polygonatum rhizomes are steamed in water until the rice wine is completely absorbed， and when the surface of Polygonatum rhizomes is black and lustrous， they are taken out， dried， and cut into thick slices， which are dried to obtain wineprepared Polygonati Rhizoma[7].

Processing with black beansBlack beans with an amount of 20% of Polygonatum are boiled and concentrated into thick black bean juice. Polygonatum rhizomes are soaked in washing water of rice  until it penetrate to the center， and then washed thoroughly. The black bean juice and Polygonatum rhizomes are added into a pot and cooked together， and water is added until it submerges the medicinal materials. The mixture is boiled with high heat， then with low heat to dryness. The materials are then taken out， sundried to semidry， steamed in a steamer until the steam appears in the upper air， and then exposed in the air overnight. One day after the exposure， the materials are steamed， dried， and exposed in the air overnight again， and the operation is repeated nine times （at least five times）[8].

Nine steaming nine dryingPure Polygonatum and an appropriate amount （about 10%） of rice wine are mixed well， and the Polygonatum rhizomes are simmered until the rice wine is exhausted. When steaming for the first time， the Polygonatum rhizomes are steamed until the center is empty （attention should be paid to the collection of Polygonatum juice during the steaming process）， and then taken out and dried until the outer skin is slightly dry. Next， the Polygonatum rhizomes are mixed with the Polygonatum juice collected and an appropriate amount of rice wine， and simmered until the excipients are exhausted. According to the method of steaming and drying for the first time， the material is steamed again， and then dried until the skin is slightly dry and then mixed with the Polygonatum juice collected and an appropriate amount of rice wine， and so forth. The steaming and drying are repeated for eight times. For the second to eighth steaming， about 70% of rice wine should be used. The remaining （about 20% of the dosage） rice wine and Polygonatum juice is mixed with the Polygonatum material， which is then steamed until Polygonatum is brownblack and shiny at the outer surface and dark brown in the center， soft in texture and sweet in taste. Finally， qualified Polygonatum rhizomes are steamed and dried to 80% dry， and then enter to the cutting process.

Conclusions

Polygonati Rhizoma is a commonly used bulk medicinal material which has the concomitant function of both medicine and foodstuff. Due to the increasing scarcity of wild resources， the demand for artificially cultivated Polygonatum rhizomes is increasing. In the process of planting Polygonatum， the soil should be kept moist， but should not be waterlogged， and attention should be paid to drainage. In addition， attention should be paid to the control of pests and diseases.

References

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[3] Editorial Board of Flora of China， Chinese Academy of Sciences. Flora of China[M]. Beijing： Science Press ， 1978. （in Chinese）.

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[7] XU RJ， LIANG J， YU NJ， et al. Structural change of polysaccharide constituents from Polygonatum cyrtonema in Jiuhua Mountain after processing[J]. Journal of Anhui University of Chinese Medicine， 2021， 40（2）： 91-96. （in Chinese）.

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Editor： Yingzhi GUANGProofreader： Xinxiu ZHU