Why is summer sowing and autumn transplanting more profitable for the Chinese medicinal herb Platycodon grandiflorus?

Based on production experience, changing the Chinese medicinal herbPlatycodon grandiflorus (balloon flower)from spring direct sowing to summer sowing and autumn transplanting results in faster seedling growth, a higher survival rate, and a yield increase of more than 25%. The roots produced have fewer forks, better quality, and fetch a higher price. To ensure that Platycodon grandiflorus emerges early, uniformly, evenly, and vigorously, the key steps of seed soaking and sprouting must be done well.

1. Seed soaking: Soak the seeds in water at 50°C, stirring constantly so the seeds are heated evenly. When the temperature drops to 20°C, rinse them with clean water until the seeds no longer lose color and are not sticky. Then soak the seeds in water at 15°C-20°C for 24 hours so they absorb water fully.

2. Sprouting: Place the fully hydrated seeds under conditions of 22°C to sprout, turning them once every 4 hours. When the temperature rises, shorten the interval between turnings. Rinse the seeds with water at 15°C-20°C every 12 hours, and they will sprout in 5-7 days. When the germination rate is about 70%, gradually lower the temperature to reach the temperature suitable for sowing. Seeds that are sprouted before sowing emerge 20-40 days earlier than those sown without sprouting, and the seedlings are of better quality.

In mid-to-late June, plow and prepare the soil. Apply 7500 kg of farmyard manure or barnyard manure and 25 kg of diammonium phosphate per mu as a base fertilizer. Make raised beds 1 m wide with furrows 30 cm wide. Use 7.5 kg of seed per mu (enough to transplant about 10 mu of field). Add 3-4 times the amount of fine soil or fine sand, mix well, and broadcast it onto the bed surface. Cover with fine soil or fine sand just until the seeds are no longer visible, then cover with a 2 cm thick layer of rice straw or wheat straw. After sowing, if the soil is dry, water the bed surface in the morning and keep the bed surface moist at all times. Seedlings will emerge completely in about 10 days (15 days earlier than spring sowing). When the seedlings are 1-1.5 cm tall, gently rake out the rice straw or wheat straw in the evening and promptly pull out weeds in the field. Apply a topdressing once in late July and once in late August, each time applying 10 kg each of diammonium phosphate and urea per mu. In dry weather, sprinkle water on the bed surface in the morning or evening; in rainy weather, drain water promptly to prevent root rot.

Field management: After emergence, pay attention to weed control. Thin the seedlings when they are 7 cm tall, with a plant spacing of 6 cm. Platycodon grandiflorus does not like heavy water; during the seedling stage, do not water unless it is too dry. After the seedlings are established, water frequently but lightly, and water before freezing. To prevent forked roots in Platycodon grandiflorus, there must be only one plant per position, especially when growth resumes in the second year, when multiple shoots per plant are most likely to appear. At this time, pay special attention and remove the extra shoots, keeping one plant per position. When fertilizing, apply more phosphorus fertilizer and less nitrogen fertilizer to prevent the plant from growing only vines and not roots. Flower buds other than those for seed should be pinched off in time.

In the nursery, the seedling density is high and the roots grow slender and long, which can avoid the forking that occurs when direct sowing is too sparse, thus laying the foundation for high yield and good quality. In early-to-mid November, when the upper end of the root is 0.3-0.5 cm thick and 20-35 cm long, it can be transplanted. Before transplanting, prepare the land well. Mix 2500 kg of farmyard manure or barnyard manure per mu with 25 kg of diammonium phosphate and spread it evenly. Level and harrow the soil finely, then make flat beds 1.3 m wide. Transplant at a row spacing of 15 cm and a plant spacing of 4-5 cm, and water immediately after transplanting. The seedlings overwinter naturally in the field and begin to grow around Qingming the following year. June to September is the peak growing season for Platycodon grandiflorus. Apply a topdressing once in late May and once in late July, each time applying 15 kg each of diammonium phosphate and urea per mu, and strengthen field management. Harvesting can be done from late October to early-to-mid November.