How to cultivate Platycodon grandiflorus? A detailed explanation of the key cultivation techniques

I. Morphology

Platycodon grandiflorusis a perennial herb, 30-100 cm tall, the whole plant smooth and hairless, the root thick and fleshy, the outer skin yellowish-brown or grayish-brown, the stem upright, the leaves ovate to lanceolate, 2-7 cm long and 0.5-3 cm wide, the apex acuminate, the margins sharply serrate, the base cuneate. The flowering period is July to September, and the fruiting period is August to October.

II. Growing environment

Platycodon grandiflorus prefers cool and moist conditions, likes light, and is cold-tolerant. The suitable temperature range for growth is 10°C-20°C, the optimum temperature is 20°C, and it can endure a low temperature of minus 20°C. The plant grows well in deep, loose and fertile humus soil or sandy loam with good drainage. It is afraid of waterlogging, and waterlogged soil easily causes root rot.

III. Cultivation techniques

1. Site selection and land preparation. Platycodon grandiflorus is a deep-rooted plant, so it is best to choose deep, loose and fertile humus soil or sandy soil with good drainage. After selecting the site, apply 30-40 kg of compound fertilizer per mu, scatter it into the ground, plow more than 30 cm deep, and level and harrow the soil fine.

2. Timely sowing. Platycodon grandiflorus is mainly propagated by seed. Spring sowing, autumn sowing or winter sowing are all acceptable, with 1.5 kg of seed used per mu. Seedling raising and transplanting can also be used, but because direct sowing gives a higher yield than transplanting, and the roots are straight with few branches, making it easy to scrape the skin for processing, the quality is good, so it is mostly used in production.

Use the drill sowing method: open furrows on the prepared seedbed at a row spacing of 21-23 cm, with a sowing depth of no more than 1 cm, and cover with soil after sowing. The wide-band drill sowing method can also be used, that is, the width of the furrow is 10 cm, the row spacing is unchanged, and soil is covered after sowing. The wide-band drill sowing method has many advantages, such as simple management and good finished product quality. With suitable temperature, seedlings emerge in about 15 days. IV. Field management

1. Reasonable close planting. Row spacing 21-23 cm, plant spacing 3-5 cm. If too dense, the plants grow thin and weak and are prone to pests and diseases. If too sparse, the yield is low. For the wide-band drill sowing method, thin the seedlings appropriately; as long as the seedlings are not crowded, there is no need to remove too many. Appropriate close planting is the key to increasing yield.

2. Cultivation and weeding. Platycodon grandiflorus grows slowly in the early stage and is prone to weeds, so they should be pulled out in time to prevent spreading and causing a weed infestation. For the planting site, first water thoroughly, and when the moisture is suitable, immediately loosen the soil shallowly once, so as to avoid the ground cracking and letting air through, which causes seedling death. Cultivation should be carried out when the soil moisture is moderate. Once the plants grow large and close the rows, cultivation and weeding are no longer needed.

3. Topdressing. During the seedling stage, about 25 kg of urea should be applied as topdressing to promote seedling growth. At the end of June, apply fertilizer for the flowering period, mainly phosphorus and potassium fertilizer, to prevent excessive nutrient consumption from flowering and fruiting that affects growth. After entering winter, apply a heavy overwintering fertilizer, and combine fertilization with earthing up. In the following spring, when the plant height is about 1 m, appropriately control the amount of nitrogen fertilizer and apply phosphorus and potassium fertilizer as topdressing, so that the stems grow thick and strong, which can prevent or reduce lodging.

4. Flower and fruit thinning. The flowering period of Platycodon grandiflorus is relatively long and consumes a large amount of nutrients, affecting root growth. Except for seed fields, thinning flowers and fruits can improve the yield and quality of the roots. In production, the flower buds can be removed manually, such as cutting off the flower buds with a sickle. Or paclobutrazol can be sprayed during the full flowering period to prevent flowering.

5. Drainage. Platycodon grandiflorus is planted at high density, so in summer when temperatures are high and humidity is high, drainage ditches should be cleared in time to prevent waterlogging and root rot, which causes reduced yield.

V. Main pests and diseases

1. Root rot

(1) Symptoms: a root disease caused by the fungus Fusarium, a member of the Deuteromycetes. The onset period is June to August. In the early stage, part of the root turns yellowish-brown and rots, then gradually expands, and when the disease is severe, the aboveground part withers and dies.

(2) Control methods: Pay attention to crop rotation and drain water in time. When planting in low-lying land or rainy areas, raised beds should be made. During land preparation, apply more base fertilizer to improve the soil and enhance the disease resistance of the plants. Applying 50-100 kg of lime powder per mu can reduce the damage, or use 5 kg of carbendazim per mu for soil disinfection. When the disease occurs, 50% thiophanate-methyl 1000-fold solution can be poured on for control. Pull out diseased plants in time.

VI. Harvesting and processing

1. Harvesting

Because of differences in region and sowing time, the harvest year for cultivated Platycodon grandiflorus also differs. Generally it is harvested in the same year, or harvested in the second year. The harvest period can be from the end of September to the middle of October in autumn, or before the buds sprout in the following spring. Those harvested in autumn are heavier and more solid, with better quality. Generally, digging is carried out when the aboveground stems and leaves wither. If dug too early, the roots are not yet plump and the dry-to-fresh ratio is low, affecting yield; if harvested too late, the skin is difficult to peel. When digging, prevent breaking the main root.

2. Processing

After the fresh roots are dug out, remove the soil and the rhizome head, scrape off the cork layer with a bamboo knife, wooden edge, porcelain piece, etc., wash clean, and dry in the sun or by artificial drying. The skin should be scraped off clean while fresh; if too much time passes, the root skin becomes difficult to scrape. After scraping the skin, dry it in time. If too many Platycodon grandiflorus roots are harvested to process all at once, they can be buried in sand to prevent the outer skin from drying and shrinking, which makes peeling easier. The dry-to-fresh ratio is 30-35%. The yield per mu is 150-200 kg in one year, and 350-400 kg per mu in 2-3 years.