The lettuce cultivation is mainly divided into two seasons: Spring and Autumn. In the suburbs of major cities such as Nanjing, Shanghai, Beijing, Chengdu, and Xi’an, sowing has started in stages, depending on local climate conditions.
**Spring Lettuce**: This variety is typically sown in the fall or early Winter , with a harvest in the following spring. The seedlings should be transplanted when they have 5–6 true leaves, ensuring strong growth and well-developed roots. Sowing too early or too late can lead to issues—seedlings that are too large or too small may suffer from frost damage once winter ends. A wet sowing method is recommended, and seedlings should be thinned 1–2 times after emergence. During the seedling stage, irrigation should be carefully controlled to make the leaves thick and flat. In open areas, winter planting should be done as early as possible before the cold sets in. For late varieties, planting can also occur in spring after the previous crop is harvested. In regions where winters are harsh, planting should take place as soon as the soil thaws in early spring. The ideal soil type is clay loam or sandy loam rich in organic matter, with good water retention and fertility. Organic fertilizer should be used as a base. The shape of the raised beds may vary by region, but spacing between rows is usually around 40 cm. Before winter, irrigation should be controlled, and careful weeding should be done to keep the soil shallow, protecting the roots and stem from frost. After the plants regreen in early spring, frequent cultivation helps increase temperature and accelerate leaf growth. When the fleshy stems begin to swell, a balanced application of nitrogen and potassium fertilizers along with irrigation is essential. After watering, top-dressing should not be delayed, and each application should be moderate to avoid cracking of the stems. Harvesting is best done when the main stem tip and the tallest leaf tip are ready. If harvesting is delayed, the stems will elongate, become fibrous, and may even hollow out, leading to poor quality.
**Autumn Lettuce**: This type is sown in Summer and harvested in late autumn. High temperatures during sowing can make germination difficult, resulting in weak seedlings that grow too quickly and develop flower buds prematurely. Controlling bolting is crucial. For mid- to late-maturing varieties, it's important to choose an appropriate sowing time that allows them to tolerate high temperatures and long days. Seeds should be soaked in cold water for 5–6 hours, then germinated under light at 15–18°C. A wet sowing method is used, with a thin layer of soil covering the seeds to provide shade and cooling. Seedlings should be transplanted when they have 4–5 true leaves. Once the stems begin to swell, apply nitrogen and potassium fertilizers.
**Seed Selection**: Spring lettuce is commonly used for seed production. Select healthy plants with clear cultivar characteristics, late bolting, dense internodes, no side shoots, few leaves, and long, non-cracked, disease-free fleshy stems. Apply nitrogen and phosphate fertilizers before flowering, and ensure adequate water after flowering. Reduce irrigation later to prevent excessive sprouting and nutrient competition. Harvest the white, umbrella-like crown of the achene when mature.
**Pests and Diseases**: Common pests include downy mildew, sclerotinia, mosaic virus, aphids, thrips, and cutworms. Regular monitoring and proper cultural practices are essential to manage these issues effectively.
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