Bok choy or pak choi is a type of Chinese cabbage. Chinese varieties do not form heads and have smooth, dark green leaf blades instead, forming a cluster reminiscent of mustard greens or celery. Wikipedia
I have planted one store bought Bok Choy that still had lot of roots on it and planted it in my new vertical garden planter.
A deep green leafy vegetable that resembles Romaine lettuce on top and a large celery on the bottom, Bok Choy is a crucifer more closely related to cabbage. The entire vegetable can be used, in stir fries or in salads.
Most vegetable gardeners growing leafy vegetables will have heard the term 'cut-and-come-again'. As a harvesting technique the term is often poorly understood, and many gardeners may not appreciate quite how useful the system is -- especially if they have just a small piece of land.