Yu choy (Brassica rapa var. parachinensis), also spelled yau choy or yow choy and known in English as choy sum or flowering oilseed rape, is a leafy cool-season brassica grown for its tender flowering shoots — slim green stalks carrying oval leaves and clusters of small four-petalled yellow flowers, all of which are eaten. It is among the most eaten leafy greens of southern China, a workhorse everyday vegetable with a robust, distinctly green, faintly mustardy flavour and a gentle bitterness. It cooks in moments and is most often blanched and dressed with oyster sauce or stir-fried hard with garlic, the stems added a beat before the leaves so both finish crisp-tender at once.