Key Technical Points for Spring Greenhouse Cultivation of Celtuce

Celtuce, also known as asparagus lettuce, is a variety of Lactuca sativa in the Asteraceae family, genus Lactuca, that can form a fleshy tender stem; it is a biennial or annual herbaceous plant. Also called stem lettuce, asparagus lettuce, green lettuce, and lettuce vegetable. Harvest period: January to April. It originated in Central or North China. The aboveground stem is edible; the stem skin is white-green, the stem flesh is crisp and tender, the young stem is emerald green, and it turns white-green after maturity. The main edible part is the fleshy tender stem, which can be eaten raw, in cold dishes, stir-fried, dried, or pickled; the young leaves are also edible. The stem and leaves contain lactucin, which contains lactucin. It tastes bitter and has an analgesic effect. Celtuce has strong adaptability and can be cultivated in spring and autumn or overwintered, mainly in spring, and harvested in summer.

Morphological Characteristics of Celtuce

The stem looks like rings, like a bamboo shoot. It has a taproot system; after transplanting, many lateral roots develop, shallow and dense, mainly distributed in the 20-30cm soil layer. The stem is shortened. Leaves are alternate, lanceolate or long ovate, etc., with colors of light green, green, dark green, or purplish red; the leaf surface is flat or wrinkled, with entire or notched margins. The shortened stem gradually elongates and thickens as the plant grows. After the stem tip differentiates flower buds, while the flower stem elongates, the stem thickens and grows, forming a club-shaped fleshy tender stem. The flesh color is pale green, emerald green, or yellow-green. It has a conical capitulum inflorescence with pale yellow flowers; each inflorescence has about 20 flowers, self-pollinating, though cross-pollination sometimes occurs. The achene is black-brown or silvery white, with a pappus attached.

Growing Environment of Celtuce

Celtuce is sensitive to soil acidity and alkalinity and is suitable for planting in slightly acidic soil. Celtuce has a shallow root system and weak absorption capacity, with a relatively high demand for oxygen; sandy loam and loam are best for growing celtuce.

Spring Greenhouse Cultivation Techniques for Celtuce

Celtuce belongs to the Asteraceae family and is heat-tolerant and cold-tolerant, and can be cultivated all year round. Using greenhouses to cultivate celtuce in spring results in a short growing period, supplies the market, and provides relatively high economic returns.

For spring celtuce in greenhouses, large and small seedlings are generally planted separately in greenhouses already covered with film in early to mid-November, with a plant spacing of 25 cm × 30 cm, and they can be marketed in mid-February. The cultivation techniques are as follows:

1. Temperature and humidity management. In the early stage after planting, attention should be paid to ventilation and dehumidification. When the nighttime temperature is above 0°C, ventilation is needed; when it is below 0°C, a small arched shed should be covered and straw curtains added; during the day, the straw curtains should be uncovered. When the stem begins to expand until before harvest, the greenhouse temperature should be 15-20°C during the day, ventilated when it exceeds 24°C, and should not be lower than 5°C at night.

2. Fertilizer and water management. After planting, sufficient water should be applied to stabilize the roots; after 5-6 days, when the seedlings have recovered, water should be applied to help them recover, and at the same time a seedling-promoting fertilizer should be applied with the water, with 10-15 kg of ammonium sulfate per mu, followed by 2-3 continuous cultivations and loosenings of the soil. When the plant begins to form a rosette, apply fertilizer again with water, with 20 kg of ammonium sulfate per mu, then continue cultivation and seedling restraint. When the stem begins to expand, water promptly, and apply 25-30 kg of ternary compound fertilizer per mu with the water. After that, the soil should be kept moist.

3. Disease control. In the early stage of disease, use 25% metalaxyl-mancozeb wettable powder at 800-900 times dilution mixed with 50% procymidone wettable powder at 1500 times dilution, or with 50% carbendazim suspension concentrate at 500-600 times dilution, and spray 2-3 times (once every 7 days).

4. Harvest. The best harvest time is when the top of the main stem is level with the tip of the highest leaf. To bring it to market earlier, it can be harvested appropriately early, harvesting the large ones and leaving the small ones, and marketing in batches.