By Dr. Mercola
Long a staple in Asian cuisine and embraced within traditional Chinese medicine, bok choy — also known as bok choi, pak choi or pak choy — is now recognized worldwide. This green leafy vegetable closely related to cabbage is characterized by large lettuce-like leaves on top and creamy, celery-like stalks on the bottom. Bok choy leaves are smooth and tender, with a flavor somewhere between cabbage and chard.
The entire vegetable is edible, and when served raw or lightly blanched, bok choy adds a satisfying crunch to salads, stir-fries and soups. Koreans love to ferment bok choy with daikon radish, garlic, ginger and scallions to make a traditional spicy side dish called kimchi. Others enjoy shredded bok choy as a coleslaw. It is also delicious when sautéed with ginger and garlic.
While you will likely find it and other varieties of Chinese cabbage in your local grocery store, you may want to try growing your own. Because bok choy matures quickly and regrows easily, you won’t regret the time spent cultivating this tasty, nutrient-dense vegetable.
How to Recognize Bok Choy
Bok choy (Brassica rapa) is a type of Chinese cabbage related to other cruciferous vegetables like broccoli, cabbage, cauliflower and kale. Bok choy is characterized by broad green leaves flaring outward from an upright head. Its stalks, which resemble a fatter type of non-string celery, can be either green or white. Bok choy flower stalks emerge from the center of the plant during warm weather and can shoot up to be twice the size of the plant.
Similar to broccoli, bok choy flower stalks are characterized by brilliant yellow clusters resembling the ribs of an umbrella. The appearance of flower stalks may indicate the end of life for this cool-season vegetable. Flowering also signals the arrival of tougher, more fibrous leaves, a bitter aftertaste and, eventually, the end of the leaf harvest.
That said, some find the flower stalks to be tasty, suggesting these tender shoots possess a flavor similar to broccoli rabe. The size of mature bok choy plants depends on the variety grown. Typically, baby bok choy is less than 10 inches tall, with a stalk diameter of about 2 to 4 inches. Standard (or large) bok choy varieties reach 1 to 2 feet tall and have an average stalk diameter of around 6 inches.
Getting Started With Bok Choy
- Bok choy is a biennial and somewhat winter hardy
- When covered, it may survive in U.S. Department of Agriculture hardiness zones 4 to 7
- As a cool-season crop, bok choy will quickly flower and bolt to seed when temperatures warm up in the spring
Soil: Bok choy will flourish in well-draining soil with lots of rich, organic matter. If your soil is lacking nutrients, use an organic fertilizer high in nitrogen. While bok choy can survive in a soil pH ranging from 6.0 to 7.5, a pH in the 6.5 to 7.0 range is ideal.
Sowing indoors: To get a jump-start on the growing season, start bok choy seeds indoors about four to five weeks before the last expected frost in your area. Plant seeds one-half inch deep, spaced 1 inch apart. Bok choy seeds germinate quickly, usually within four to eight days.
Sowing outdoors: You can direct seed bok choy outdoors, in containers or your garden bed, beginning one to two weeks before the date of your last expected frost. The planting instructions for indoor sowing also apply outdoors.
Sun: While bok choy can handle full sun, it will thrive in partial shade. So, plan for your plants to receive three to five hours of sun daily. In summer, partial shade can prevent your plants from premature bolting.
Thinning: For best results you will want to thin plants when they have a couple of inches of growth. For full-sized bok choy, thin to allow for at least 6 to 8 inches of spacing between plants. The thinned plants are edible and will be tender and delicious, so be sure to eat them!
Transplanting: Bok choy transplants do better when you wait until nighttime temperatures are consistently maintained above 50 degrees F. If you move them outdoors in cooler temperatures, be sure to cover them. When exposed to frost or prolonged cold temperatures, bok choy plants may mistake it for winter and start to bolt as soon as the weather warms up.
Water: When planting bok choy, be sure to water your starter soil and garden bed well both before planting the seeds and immediately after. During the growing season, bok choy requires consistent watering, especially in the fall. Dry conditions will result in less juicy ribs and may also cause premature bolting.
Bok Choy Pests and Problems
Fortunately, bok choy is not usually affected by the common diseases that damage other members of the brassica (cabbage) family.3 It can, however, be disturbed by many of the insect pests, including cabbage loopers and cabbage worms, common to other cabbages. Use floating row covers to minimize damage from those pests as well as flea beetles, which can riddle the leaves in early spring. Aphids, slugs and white flies can also do harm to bok choy leaves.
Four Ways to Grow and Harvest Bok Choy
According to Rodale’s Organic Life, you have your choice of four basic ways to grow and harvest bok choy:4
1. Baby bok choy: Plant seeds for these fast-maturing dwarf varieties 3 to 4 inches apart in every direction. Slice entire mini-heads off at the soil level when they reach a desirable size or as soon as you see the tip of a flower stalk rising out of the center of the plant. For a continuous supply, you can plant a few dozen seeds every two weeks throughout the spring and, if desired, again in midsummer to fuel your fall harvests.
2. Baby bok choy greens. Ready to harvest in as little as 30 days, baby leaves are the speediest way to grow bok choy. You’ll want to plant about 60 to 100 seeds per square foot in your garden. As soon as the plants reach 4 to 5 inches tall, you can begin harvesting the leaves by cutting about 1 inch above the base of the leaves.
After the initial cutting, your plants should continue to grow more leaves, allowing for at least one or two more harvests. For a continuous supply of fresh greens, be sure to plant new seeds every four to six weeks throughout the growing season.
3. Individual ribs and leaves. For this method, you should cultivate bok choy as you would for whole, mature plants (see below), but start harvesting as soon as the first outer leaves present with fat crisp ribs. This usually happens in about 45 to 60 days after seeding.
For intermittent harvesting (as for individuals and small families), bend individual leaves away from the plant and gently press down on the base of each rib to separate it from the central stem. For a continuous supply, plant a few seeds every four weeks throughout the spring and again in midsummer if you want a fall harvest.
4. Whole mature plants. This method requires the most patience since large bok choy plants can take from 60 to 80 days to fully mature. As mentioned, you can shorten the time in the garden by starting seeds indoors and transplanting when overnight temperatures stabilize around 50 degrees F. For a continuous supply, plant a few seeds every two weeks during springtime and again beginning in midsummer if you want a fall harvest.
Types of Bok Choy and Tips on Harvesting
Given proper growing conditions, and depending on the variety, weather and climate, the most common types of bok choy reach maturity in about 45 to 60 days. Despite the availability of literally dozens of varieties, seed packets may be generically labeled “bok choy,” without reference to a specific variety name. When identifiable, a few of the varieties you may want to consider planting include:5,6
- Black Summer: A dark-leafed variety maturing in 45 days, which is ideal for fall planting and winter harvesting
- Ching-Chiang: Quick-growing dwarf known to produce 14-inch plants with smooth, medium-green leaves in about 40 days
- Joi Choi: Medium-sized plant maturing in 45 to 55 days that is valued for its resistance to bolting and cold temperatures
- Mei Qing Choi: Fast-growing hybrid dwarf ready in 35 to 45 days
- Win-Win: Producer of extra-large dense heads in about 52 days and slow to bolt
The best technique for harvesting bok choy is to use a sharp knife to slice the plants off about 1 inch above the ground. (Remember, using the right knife can increase nutrients.) In doing so, bok choy will automatically regrow a second time. The new crop will be characterized by smaller, yet equally tasty, leaves and stalks.
Eating Bok Choy
Besides using it in stir-fries, raw bok choy adds a satisfying crunch and loads of nutrition to salads or sandwiches. Feel free to eat it raw as you might celery sticks, or add it to soups and stews. While some steam it and eat it with a little salt and pepper, others enjoy sautéing it with ginger and garlic. In virtually any recipe, you can substitute bok choy for other cabbages — as in coleslaw, for example. As with the Korean specialty kimchi, bok choy can also be fermented. If that sounds appealing, check out my Korean kimchi recipe.
Health Benefits of Bok Choy
As a dark green leafy vegetable, bok choy is a rich source of vitamins A, C and K, as well as minerals such as calcium and iron. Due to its standing as a nutrient-dense food, bok choy is featured on my Healthiest Vegetables List. Following are some of the health benefits of bok choy:7,8
Builds healthy bones
The calcium, iron, magnesium, phosphorous and zinc in bok choy, as well as its healthy amounts of vitamin K, support your body in building and maintaining healthy bone structure and strength.
Decreases blood pressure
Calcium, magnesium and potassium, all of which are present in bok choy, have been found to decrease your blood pressure naturally. One cup of bok choy contains about 20 percent of your recommended dietary allowance of potassium, which acts as a vasodilator to relieve tension on your blood vessels, thereby reducing the strain on your cardiovascular system.
The vitamin C found in bok choy helps stimulate the production of white blood cells, while selenium also plays a role in fighting infection by stimulating production of your body’s killer T-cells.9
Bok choy is a good source of vitamin A, including the carotenoids lutein and zeaxanthin — antioxidants known to protect your eyes and lower your risk of age-related macular degeneration. Vitamin A has long been associated with eye health and the prevention of macular degeneration and oxidative stress in the retina.
Possesses anticancer properties
Bok choy and some of its cruciferous cousins are known to possess anticancer properties through the presence of powerful antioxidants like vitamins A and C and phytonutrients such as isothiocyanates, lutein, sulforaphane, thiocyanates and zeaxanthin, which stimulate detoxifying enzymes and may protect against cancers of the breast, colon, lung and prostate. Folate and selenium also play anticancer roles.
Promotes healthy skin
Bok choy’s rich stores of vitamin C support your body’s need for collagen, which is vital for healthy, supple skin. Vitamin C is a powerful antioxidant useful for preventing skin damage caused by pollution, smoke and sun. Vitamin C also promotes collagen's ability to reduce wrinkles and the signs of aging by improving the overall texture of your skin. The iron and zinc in bok choy also play a role in collagen production and maturation.
Whether you’ve been enjoying bok choy for years or have yet to try it, it’s a tasty, nutrient-dense vegetable well worth your time. As you make plans for your garden this year, I hope you will consider growing bok choy. If you do grow your own, you might want to try fermenting it, especially given the many benefits of fermented foods.