Spring or summer.

The production period of lettuce is from January to April.

Lettuce originates from the Mediterranean coast and was introduced to China around the fifth century.

The above-ground stems are edible. The stem skin is white-green, the flesh of the stem is crisp and tender, the young stems are green, and turn white-green when mature.

The main edible fleshy tender stems can be eaten raw, cold, stir-fried, dried or pickled, and the young leaves can also be eaten.

The stems and leaves contain lettuce, which contains lettuce (C11H14O4 or C22H36O7).

It tastes bitter and has analgesic effect.

Lettuce has strong adaptability and can be cultivated in spring and autumn or overwinter. It is mainly cultivated in spring and harvested in summer.

Extended information: Nutritional value Lettuce is rich in nutrients, especially in the leaves.

Every 500 grams of fresh lettuce leaves (Beijing area) contains 10 grams of protein, 2.5 grams of fat, 16.5 grams of carbohydrates, 190 mg of calcium, 185 mg of phosphorus, 5.5 mg of iron, 10.7 mg of carotene, 0.6 mg of vitamin B2, and vitamins

C75mg etc.

But the content in the stems is much lower. Every 500 grams of lettuce stems contains only 1.5 grams of protein, only 0.2 grams of fat, only 4.7 grams of carbohydrates, and very little carotene and vitamin C.

Eating more lettuce is very beneficial to children's growth and development. Eating 200 grams of lettuce leaves a day can meet their carotene needs, and eating 500 grams of lettuce leaves can meet their vitamin C needs.

In addition, it is also rich in phosphorus and calcium, which is very beneficial to promoting the normal development of bones, preventing rickets, and helping normal teething.

Baidu Encyclopedia-Lettuce