Bok choy, pak choi, pichay/petsay, or pok choi is a type of Chinese cabbage. Chinensis varieties do not form heads and have green leaf blades with lighter bulbous bottoms instead. Maximize the shelf life of bok choy, refrigerate in a plastic bag and do not wash until ready to use. Properly stored, bok choy will usually keep well for about 3 to 4 days in the refrigerator.