Asparagus lettuce萵苣筍

Celtuce (Lactuca sativa var. asparagina, augustana, or angustata), also called stem lettuce, celery lettuce, asparagus lettuce, or Chinese lettuce, is a cultivar of lettuce grown primarily for its thick stem, used as a vegetable
The stem is usually harvested at a length of around 15-20 cm and a diameter of around 3-4 cm. It is crisp, moist, and mildly flavored, and typically prepared by slicing and then stir frying with more strongly flavored ingredients.
...............................
Climatic requirements:
Cool season crop. Mean temperature 50-60 F.
Propagation and care:
It should be planted from the seed in the fall, winter, or early spring, spaced at about 8 inches in the row and treated like regular lettuce. Soon after the development of the outer leaves, a central stalk bearing tiny leaves at the top starts to grow. When the stem is 12 to 18 inches long cut it off down into the leafy part of the plant. Peel the stem because the outer edges contain a bitter milky sap. The soft, translucent, green central core is the edible part.
........................................
It is a cool season crop. Seeds germinate poorly when temperature is high. Usually, optimum germination temperature is 15-20℃. Except special summer cultivars, most celtuces are sensitive to bolting in hot summer. Shortage of water and fertilizer as well as big day-night temperature difference may contribute to premature bolting. Recommended planting density: 20-26cm between plants in a row. For commercial production, transplanting is recommended.
The stem is used for vegetable in China. however, the leaves may be eaten in salads at a young tender stage.
http://www.agrohaitai.com/rootstem/celtuce/celtuce.htm