A Detailed Guide to the Growth Habits and Cultivation Techniques of Lettuce

Lettuce is also known as goose lettuce, mai zai cai, and wu zai cai. It is an annual or biennial herbaceous crop that can be eaten raw; it is crisp and refreshing with a slight sweetness. So let us take a look at the cultivation techniques for lettuce.

Growth Habits of Lettuce

Lettuce prefers a cool environment; it is neither cold-tolerant nor heat-tolerant. The suitable temperature for growth is 15°C-20°C, and the growth period is 90-100 days. The seeds are relatively tolerant of low temperatures and can germinate at 4°C. The optimum temperature for germination is 18-22°C; above 30°C, they almost do not germinate.

During the plant's growth period, it prefers a cool climate, growing best at 15-20°C with high yield and good quality; when continuously above 25°C, growth is poorer, the leaves become coarse and old, and there is a slight bitter taste. However, it is also quite cold-tolerant; 0°C or even short periods of subzero low temperatures do not greatly hinder growth.

Lettuce has a well-developed root system, and the leaf surface has a waxy coating, giving it fairly strong drought tolerance, but when cultivated in fertile, moist soil, the yield is high and the quality is good.

The suitable soil pH is 5.8-6.6.

Cultivation Techniques for Lettuce

Selecting and Sowing Good Seed

Suitable varieties should be selected according to need, such as glass lettuce, Emperor, Caesar, head lettuce, oakleaf lettuce, Dahoo 659, and others.

Preparing the Seedbed

For raising lettuce seedlings, it is advisable to choose fertile sandy loam with good water- and fertilizer-retention capacity. Seedbed soil preparation: for a 10 sq m seedbed, use 10 kg of decomposed organic fertilizer, 0.3 kg of ammonium sulfate, 0.5 kg of superphosphate, and 0.2 kg of potassium sulfate; mix thoroughly, spread flat, and rake fine; water thoroughly to saturate the bed, and sow after the water has seeped in.

Sowing and Raising Seedlings

To ensure even broadcasting, a small amount of fine sandy soil can be mixed into the seeds when sowing. After sowing, cover with 0.3-0.5 cm of moist soil and cover with plastic film to retain moisture. The sowing rate is 30-50 grams per mu. When the seedlings begin to emerge, the plastic film on the bed surface should be removed promptly to prevent leggy growth. The seedbed temperature should preferably be controlled at 18°C-20°C during the day and 12°C-14°C at night. Pay attention to ventilation; if there is strong sunlight exposure, shade is needed. When the seedlings grow to 2-3 true leaves, transplant them at a spacing of 6-8 cm between plants and rows; when they grow to 4-5 true leaves, they can be planted out. During the seedling stage, generally do not water unless there is a water shortage. To prevent seedling-stage diseases, spray 1-2 times with a 600-fold dilution of 75% chlorothalonil solution.

Scientific Fertilization

Lettuce requires clay loam rich in organic matter with strong water- and fertilizer-retention capacity. Lettuce prefers slightly acidic soil, with a suitable soil pH of 5-7. For every 1000 kg of lettuce produced, it absorbs 2.5 kg of nitrogen, 1.2 kg of phosphorus, and 4.5 kg of potassium. Among these, head lettuce requires more potassium. During the growing period, nitrogen, phosphorus, and potassium fertilizers need to be used in combination. The plot for planting lettuce should be deeply plowed and carefully prepared; before planting, apply sufficient base fertilizer, with 3000-3500 kg of decomposed farmyard manure per mu; after application, plow deeply, water thoroughly to saturate the soil, and make beds after the soil surface dries.

Careful Planting Out

The day before planting out, irrigate the seedbed to moisten the seedling clumps; on the second day, lift the seedlings with as much soil as possible to reduce root damage. When planting out, first open furrows on the bed surface, 4-6 cm deep; on a 70 cm bed surface, plant 3 rows. After opening the furrows, apply 25 kg per mu of compound fertilizer and then irrigate; after the water seeps in, place the seedlings at a spacing of 24 cm between plants, earth up, and close the furrows; rake the bed surface level, cover with plastic film, and draw the seedlings out through the film.

Management After Planting Out

Lettuce prefers moisture and requires a sufficient water supply throughout the entire growth period. Water once with recovery water 5-7 days after planting out. After watering with recovery water, for plots not covered with plastic film, carry out 2 rounds of intertillage, loosening the soil, and weeding. Afterward, water 3-4 times, and in conjunction with watering, apply nitrogen and phosphorus fertilizers in stages, at 15-20 kg per mu. Stop watering before harvest to facilitate storage and transport.

Scientific Harvesting

Non-heading lettuce can be harvested flexibly according to market prices. Head lettuce is best harvested after the leaf heads are firm; harvesting too early will affect yield, while too late will cause the stem inside the leaf head to elongate, the leaf head to loosen, and quality to decline.