Bok choy (Brassica rapa var. chinensis) is a cool-season vegetable usually grown as an annual. Bok choy produces heads of white, celerylike stalks with tender leaves that are deep green in color. Both the leaves and stalks are edible. Its mild flavor makes it useful in soups and stir-fries. When you harvest your bok choy depends on whether you want to use the stalks, leaves or both.
Bok Choy Basics
Bok choy can grow in fall or spring -- or both -- depending on your climate. For the plants to thrive and the seeds to germinate, bok choy needs temperatures between 50 and 80 degrees Fahrenheit.
Provide your bok choy plant with full sun. It can also grow in partial or filtered shade. Rich, moist, well-draining soil with plenty of organic matter is a must. Bok choy tolerates soils ranging from slightly acidic to slightly alkaline -- a pH range of 6.0 to 7.5. Boy choy heads are usually ready for harvest within 45 to 60 days after planting. Baby bok choy varieties, such as "Green Baby" and "Riko Baby" mature faster than their full-sized counterparts.
Bok choy tolerates cooler temperatures but does not handle frost. Start your bok choy seeds and transplant the seedlings outdoors after the threat of frost has passed. When starting your plants indoors in flats, plant seeds four to six weeks before the last frost date.
If you are starting your plants outdoors, sow the seeds 1/2 inch deep in the soil in rows that are 2 to 2 1/2 feet apart. Allow 6 to 12 inches of space between plants. Bok choy plants begin to emerge within four to seven days of planting the seeds.
Harvesting the Leaves
You can harvest bok choy leaves from your plants as soon as three weeks after the plants have emerged. If you wait until four weeks, the leaves are larger and have more flavor. To ensure your plants continue to produce new leaves throughout the growing season, cut or pick the leaves at the start of the white stem. Choose leaves from around the outside of the plant. Leave the inner leaves on the plant to stimulate new leaf production. Always pick off and remove wilted, dead or diseased leaves to ensure that your bok choy plant remains healthy and vigorous.
Bok choy heads are ready for harvest anywhere between one and 56 days after reaching maturity. Use your judgment and allow heads to remain in the ground if you want them to grow some more. It is possible to harvest bok choy heads before they reach maturity, but this decreases the production of your plants.
Mature bok choy is generally 12 to 16 inches long at maturity. To harvest the heads, cut the bok choy at the base of the stalks, leaving a few leaves behind to encourage new head production. If you notice your bok choy heads cracking or splitting, this is typically a sign of excess nitrogen or lack of water. Harvest cracked or splitting heads immediately to prevent the head rotting or dying.