Choy sum is a green leafy vegetable similar to gai lan, and can be characterized by the distinct yellow flowers which it bears. Each flower has four yellow, oval to round petals with six stamens on fleshy, erect stems which are 0.5-1.0 cm in diameter and 15-20 cm tall with light to dark green, and are oval (becomes acuminate shaped, or basal-shaped near the flowering stage) with slightly serrated margins leaves, which never forms compact heads like the cabbage. When selecting, choose greens that are not wilting nor contain brown spots. The stalks should be firm and not limp or fibrous looking. To prepare, wash the greens thorougly and then trim a small amount from the bottom of the stalks. The stalks can be served cooked until wilted but retain the crunchy texture. The greens can be prepared by boiling, steaming or stir-frying. If blanched to eat as a vegetable, choy sum can be served at room temperature and dressed lightly with soy sauce or a sesame oil. To store, place the greens in a plastic bag and refrigerate.