The appearance of lettuce is:

The height of lettuce is 25 cm to 100 cm, the stem is upright, solitary, the basal leaves and lower stems and leaves are large, undivided, and draped upside down. Needle-shaped, oval or oblong-lanceolate, with sharp, short acuminate or rounded top, without handle.

The leaves at the lower part of the panicle branches and the leaves on the panicle branches are very small, egg-shaped, heart-shaped, and sessile. There are many or very many flower heads, arranged in panicles at the tops of stems and branches.

The growth habits of lettuce:

Lettuce is a cold-tolerant vegetable that likes cold climates and is not resistant to high temperatures. The temperature for germination is above four degrees Celsius, with fifteen to twenty degrees Celsius being the best. If the temperature exceeds thirty degrees Celsius, there will be no germination.

The seedlings can withstand subzero temperatures. The suitable temperature for seedling growth is 15 to 20 degrees Celsius, and the growth temperature of the stems is 11 to 18 degrees Celsius. Lettuce likes a large temperature difference between day and night, and requires higher temperatures for flowering and fruiting. The optimum temperature is 19 to 22 degrees Celsius.