When to Plant Lettuce? Introduction to the Latest Planting Times
Lettuce is an annual or biennial herbaceous crop of the genus Lactuca in the Asteraceae family, native to the Mediterranean coast of Europe and domesticated from wild species. It was first eaten by the ancient Greeks and Romans, and has a long history of introduction into China, with more cultivation in the southeastern coastal areas, especially the outskirts of major cities and the Guangdong and Guangxi regions. Now let us take a look at when lettuce should be planted!
Growth Habits of Lettuce
Lettuce prefers a cool environment; it is neither cold-tolerant nor heat-tolerant. The suitable growing temperature is 15-20°C, and the growth period is 90-100 days. The seeds are fairly tolerant of low temperatures and can germinate at 4°C. The optimum germination temperature is 18-22°C, and they barely germinate above 30°C. During the growing period it likes a cool climate, growing best at 15-20°C with high yield and good quality. Growth is poorer when the temperature stays above 25°C, but it is also quite cold-tolerant, and 0°C or even short periods of sub-zero low temperatures do not greatly hinder its growth. It has a well-developed root system and waxy leaves, and is fairly drought-tolerant, but when cultivated in fertile, moist soil it produces high yields and good quality. The suitable soil pH is 5.8-6.6.
Sowing Time for Lettuce
Lettuce likes a cool climate, so sowing is generally done in spring and autumn. In spring, sowing usually starts from February to April, and harvest can be done from May to June; for autumn sowing, it can start at the end of August, and harvest can be done from September to October. Because different varieties of lettuce have different characteristics, when choosing the sowing time you should first read the instructions for the lettuce seeds you bought, and then sow according to the sowing times above. Spring and summer are suitable for sowing loose-leaf lettuce (such as butterhead lettuce and colored-leaf lettuce), which is more heat-tolerant; autumn and winter are suitable for sowing head lettuce (also called iceberg lettuce), which is not heat-tolerant.
Sowing Methods for Lettuce
1. Sowing: Lettuce seeds are too small and light, so they need to be mixed with fine sand, stirred evenly in a container, and then scattered onto the soil, covered with 0.5-1 cm of soil, just a thin layer. At 15-20 degrees they germinate in about 3-5 days; when the temperature is above 25 degrees germination is difficult. When planting in summer, the seeds need to be pre-germinated: soak the seeds for 1 night, then wrap them well in a damp gauze and put them in the refrigerator's cold storage compartment (about 5 degrees), and sow when more than half of the seeds have sprouted.
2. Seedling stage: During the lettuce seedling stage, keep the soil moist and not dry, and keep the soil well-drained. Thin the seedlings when there are 2-3 true leaves, with a plant spacing of 5-8 cm.
3. Transplanting: When the lettuce seedlings grow to 5-6 true leaves, transplant them. Before transplanting, water thoroughly, and move them together with the soil on the roots into a large pot. For loose-leaf lettuce, the plant spacing is 15 cm, and 30 cm for head lettuce. Water thoroughly. In summer, first place them in a shady spot to recover; after about 1 week, once the roots have taken hold, give them normal sunlight.
4. Fertilizing: One week after transplanting the lettuce seedlings, apply fertilizer once (nitrogen-based fertilizer, with well-rotted organic fertilizer being best). Two weeks and four weeks after transplanting, apply organic fertilizer or a compound fertilizer based mainly on nitrogen, phosphorus and potassium once each. Stop fertilizing 2 weeks before harvest.
5. Watering: When lettuce is grown in high temperatures, water in the early morning and evening; small amounts and frequent watering are best, but avoid waterlogging. In the early growth stage it is suitable to control water, keeping the soil just moist.