Celtuce

Lactuca sativa var. asparagina

Other names: celery lettuce, asparagus lettuce, stem lettuce, Wo Ju, Woo Chu, Wo Sun, Stemuretasu, Kaki-Jisha.
Celtuce is native to China. It is mostly grown in South China. 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: 20-30cm between plants in a row. For commercial production, transplanting is recommended.
The stem is used for vegetable in China. The leaves can be used as lettuce for salads.