What are the key techniques for field cultivation of Houttuynia cordata (fish mint)?

1. Selecting seed stems. Houttuynia cordata is not propagated from seed; its rhizomes are used as planting material. Choose stems from non-flowering plants that are thick and plump, have long internodes, and have few root injuries. The seed stems should be at least 5 to 6 cm long, preferably 15 to 20 cm. Generally, it can be planted in all four seasons. However, to ensure the survival rate, it is best to choose spring, when the seed stems have just sprouted and transplanting makes it easy to survive.

2. Land preparation and basal fertilizer. Choose a field with convenient irrigation, and after thorough land preparation, make raised beds. Apply basal fertilizer during land preparation: 3000 to 5000 kg of farmyard manure, 50 kg of compound fertilizer, 50 kg of superphosphate, 15 to 20 kg of potash fertilizer or 100 kg of plant ash per mu.

3. Opening furrows and sowing. On the raised beds in the field, open a longitudinal furrow every 35 cm, with a depth of generally 8 to 10 cm. In the furrow, plant one Houttuynia cordata stem every 7 to 10 cm. After arranging them, carefully cover the planting stems with fine soil; the seed stems must not be left exposed on the soil surface.

4. Weeding and irrigation. Houttuynia cordata is easily crowded out by weeds. Therefore, after sowing, immediately spray the whole field once with glyphosate and acetochlor, and thereafter apply acetochlor once every 20 days. After Houttuynia cordata covers the entire field, switch to hand-pulling weeds. Houttuynia cordata likes moisture but fears waterlogging. For irrigation, furrow irrigation and sprinkler irrigation are best; flooding irrigation is not suitable. Ensure that the bed surface has no water while the bed furrows hold accumulated water.

5. Fertilizer management. After sowing, starting from when the seedlings are uniform, apply a topdressing every 10 to 15 days, each time with 30% human manure and urine. In the peak growing season from May to June, switch to 50% human manure and urine, 1500 to 2000 kg per mu each time, and add about 10 kg of urea per mu for the final application. After Houttuynia cordata closes its rows, no more fertilizer is applied between the rows, but foliar topdressing can be done by spraying 0.1% to 0.2% monopotassium phosphate, with about 50 kg of mixed water-fertilizer solution per mu. After Houttuynia cordata grows larger, to direct nutrients to underground stem growth, the flower buds should be removed promptly.

6. Harvesting. Both the leaves and underground stems of Houttuynia cordata can be eaten, but in the first year of planting, the leaves should not be harvested. From February to April of the second year, tender leaves and underground stems can be harvested. May and June are the peak growing season for Houttuynia cordata, so it is not suitable for harvesting. From July to September, tender leaves can be harvested, and from September of that year to March or April of the following year, underground stems can be harvested.

7. Disease control. Houttuynia cordata generally has few insect pests. Common diseases include southern blight, root rot, purple blotch, and leaf spot. In general cultivation, diseases are rare within 1 to 2 years and only begin to appear successively from the 3rd year. Diseased plants should be promptly dug out with roots and soil, and pentachloronitrobenzene should be sprinkled into the holes for disinfection; then spray the field with 1:1:100 Bordeaux mixture or 25% triadimefon wettable powder 1000-fold solution, or spray with 50% thiophanate or 50% Tuzet 250 to 300-fold solution.