Douban Green Cultivation Method: Watercress green thrives in a soil rich in humus. A suitable potting mix can be made by combining 4 parts of peat or humus soil, 2 parts of sawdust, 1 part of perlite or river sand, and 3 parts of garden soil. During the growing season, maintain high humidity levels in the air. In hot weather, place potted plants in a cool, well-ventilated area away from direct sunlight. Water more frequently and mist the leaves to keep them vibrant and healthy. Although Douban green is drought-resistant, overwatering can lead to root rot. Water only when necessary, keeping the soil consistently moist but not soggy.
In winter, reduce watering and avoid using cold water. It's best to use water that’s close to room temperature. Fertilize every 2–3 weeks between May and September. In spring and summer, keep the plant in a semi-shaded spot, and during winter, place it in a sunny location but avoid direct sunlight. The ideal winter temperature should be above 10°C. To maintain lush foliage, repot every 2–3 years or replace the container as needed. When the plant reaches about 10 cm in height, pinch off the center to encourage side branch growth and keep the plant compact and full.
Soilless Cultivation Method: For soilless cultivation, a suitable substrate can be made with a mix of vermiculite, peat, and slag in a 1:1:1 ratio, or perlite, peat, and river sand in the same proportion. Use a foliage plant nutrient solution or a balanced flower fertilizer. When planting, add a layer of gravel or coarse sand at the bottom of the pot, place the seedling in the center, and fill with the substrate. Water the first time until the excess drains out from the bottom tray. After that, top up with 50–100 ml of nutrient solution weekly for small to medium pots. Keep the substrate moist, and maintain a pH around 6.5.
During the growing season, mist the stems and leaves once or twice daily to help retain moisture, especially in dry or hot conditions. Watercress is quite shade-tolerant and can thrive indoors in bright, indirect light. In winter, it benefits from more sunlight. Keep the room temperature above 15°C, and reduce watering frequency to prevent leaf rot. This method helps ensure healthy growth without the need for traditional soil.
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