Choy sum (sometimes known as white choy sum or more ambiguously as Chinese leaves) is a green leafy vegetable used in Chinese and South-east Asian cooking. It has firm white stems and dark green leaves. It is actually a member of the cabbage family (brassica chinensis, or brassica campestris, Chinensis group). Unlike a conventional western cabbage, the heads are very loose and outward fanning instead of closing in on themselves.
Choy sum properly refers to a vegetable that has stalks that are about 1" wide with some vertical space between them. Choy sum is sometimes confusingly used to refer to the tender innermost part of any related vegetable.
Choy Sum is related to:
- bok choy - 2"-wide stalks with very little vertical spacing, more bitter, more likely to be damaged due to larger size
- yu choy - 0.4"-diameter branching stems, rarely sold, may include flowers
- Chinese cabbage - tight head (Pekinensis group), very common