Crisp and loose-headed, the kind of Chinese cabbage known as pak choi or bok choy (Brassica rapa var. chinensis) -- and a handful of other spelling variations -- is a versatile Asian green that is used fresh in salads, stir-fries and casseroles. You have dozens of varieties of pak choi from which to choose, including 'Green Baby,' which is ideal for growing in containers; 'Summer Boy,' which does well in warm climates; 'Joi Choi' for cooler regions and 'Mei Qing Choi,' which flourishes in a range of temperature conditions. Either sow pak choi seeds or plant seedlings.
Sow pak choi seeds in the ground about 4 inches apart within their rows, leaving 18 inches between the rows. The seeds need to be sown at a soil depth of 1/2 inch. Water the area thoroughly after sowing.
Thin the seedlings that emerge, removing enough so that the remaining plants are about 18 inches apart in all directions. Alternatively, set pak choi seedlings or transplants into the ground at a spacing of 18 inches apart in rows that are 18 inches apart.
Set a 2-inch-thick layer of straw, finely chopped bark or another mulch material around -- but not touching -- the plants. Mulch suppresses weeds and keeps roots cool during the hot days of summer.
Keep the pak choi bed evenly moist as the plants grow, aiming for the top 6 inches of soil to be moist after each watering. Long-growing pak choi cultivars benefit from the addition of a handful of compost worked into the top few inches of soil near the base of each plant. Do this about halfway through their expected growing season. Avoid disturbing the plants' roots.
Harvest the whole heads of the pak choi when they reach maturity, which happens about 30 to 55 days after sowing the seeds, depending on the variety. Your seed packet should include the average maturity date for the specific pak choi cultivar.