Joi ChoiÂ is an excellent variety with dark green leaves and pure white stems which grow uniformly and neatly. ItÂ isÂ slow to bolt and has a good frost resistance. Pak Choi has been grown in China for about 1500 years. It is used whole when it is about 10cm tall or grown larger so that the individual leaves can be used. Pak Choi can be used raw in salads but when it is cooked, it is slightly spicy in taste.