Lettuce, like lettuce, is also called lettuce, an annual or biennial herb. It is 25- 100 cm high, the stem is upright and solitary, the basal leaves and the lower stems and leaves are large and undivided, oblanceolate, oval or elliptical, with a sharp tip, a short cone or a circle, and no stalk. The leaves on the lower part of the spike and the upper part of the spike are extremely small, egg-shaped and heart-shaped, and sessile.

The heads are numerous or extremely numerous, arranged in panicles at the top of stems and branches. Achenes are oblanceolate, compressed, light brown, sharp-pointed, and slender, almost as long as achenes. The flowering and fruiting period is from February to September.

Extended data

Growth habit: Lettuce is a cold-resistant vegetable, which likes cold climate and is not resistant to high temperature. The germination temperature is above 4℃, and 15-20℃ is the best. If the temperature exceeds 30℃, it will not germinate. Its seedlings can tolerate sub-zero low temperature, the suitable temperature for seedling growth is 15-20℃, and the growth temperature for stem is 1 1- 18℃. Lettuce likes a large temperature difference between day and night, so it needs a higher temperature for flowering and fruiting, and the optimum temperature is 19-22℃.

It is extremely sensitive to the state of soil surface water and needs continuous water supply to keep the soil moist. And is suitable for growing in clay loam or loam with rich organic matter and water and fertilizer conservation. Lettuce likes slightly acidic soil, and the suitable soil pH is around 6.0.