How to Grow Bok Choy (Brassica rapa subsp. Chinensis L.)

How to Grow Bok Choy (Brassica rapa subsp. Chinensis L.)

Bok Choy growing

By Erin Marissa Russell

Ready to grow some bok choy? This member of the Brassica family has been cultivated by Asian gardeners for over 1,000 years. That’s likely why most of us are most familiar with this cruciferous vegetable as a part of Asian cuisine, served either on its own (check out our recipe for grilling baby bok choy) or as part of stir fries, soups, congee, dumplings, egg rolls, and noodle dishes.

Bok choy has a fresh taste that falls somewhere between that of cabbage and that of chard. Gardeners in USDA Hardiness Zones 2 through 13 can grow their own bok choy in their garden, in containers, or even indoors.

First, you should be aware that bok choy goes by a ton of different names with even more spelling variations. You may see this tasty member of the Brassica family referred to as any of the following.

  • Baak choi
  • Bok choi
  • Cai thia
  • Cai trang con
  • Canton pak choy
  • Celery cabbage
  • Celery mustard
  • Chinese cabbage
  • Chinese chard
  • Chinese Savoy
  • Chongee
  • Japanese white celery mustard
  • Joi choy
  • Lei choy
  • Mustard cabbage
  • Osaka-na
  • Pai tsai white stalk
  • Pak choy
  • Pak choy sum
  • Paksoi
  • Pak toy
  • Paktsoi
  • Piao’erbai
  • Qingjiang cai
  • Shakushina
  • Shanghai baicai
  • Shanghai qing
  • Spoon cabbage
  • Taisai
  • Tak tsai
  • Tatsoi
  • White mustard cabbage
  • Xiaoqing cai

The classic bok choy is a green biennial plant with white stems in the middle of each leaf, but varieties are available with green stems as well. Plants grow in an upright barrel-shaped formation with very thick stalks that resemble celery (without the strings).

Bok choy grow to reach heights between 10 inches and 24 inches with a 12-inch spread, and the stalk can stretch to heights twice that of the rest of the plant. Baby bok choy is generally less than 10 inches tall. When the plant goes to seed, it produces a flowering stalk that grows from the center of the plant and blossoms in the yellow four-petal cross that is commonly seen with cruciferous vegetables.

Varieties of Bok Choy

Bok choy has a long history of cultivation, so there are a variety of heirloom and hybrid species that gardeners can choose from. A selection is listed below, with a bit of information about each one. Choose the type of bok choy that sounds like it will do best in your climate and with the soil and sun you have available in your garden.

Asian Delight: Asian Delight is a unique variety of bok choy, with distinctive ruffled leaves in a deep shade of emerald green with contrasting white stems. It produces dense, compact heads that are heavy even when harvested at the miniature or baby size. The flavor of this species is mild, and heads grow up to 8 to 10 inches tall and 5 to 7 inches wide. This variety is exceptionally resistant to both heat and bolting, resulting in a longer harvest period and increased yields as compared to similar varieties that are not as adaptable—generating harvests of double the yield of similar varieties or even more, as a matter of fact. Growing as a winter crop is an option in regions that have temperate weather. 2018 All American Selections National award winner; 30-50 days to maturity.

Black Summer: Black Summer produces heads of dark green leaves that grow from light green stems instead of the traditional white stems. This variety performs best when the bok choy is allowed to grow to full size instead of being harvested as mini or baby bok choy, though it is suitable for mini heads as well. Black Summer is known for being very slow to bolt, and it is a little smaller than most bok choy varieties, growing to 10 to 12 inches tall. 45 days to maturity.

Ching-chiang: This variety of bok choy is an early maturing dwarf type that is excellent when harvested for baby bok choy. The Ching-Chiang species is a bit sturdier and stockier than most other dwarf bok choy varieties. It’s known for its mild taste and tender leaves that are light on the stringiness that can be bothersome with some types of bok choy. Ching-Chiang is well suited for planting in early spring, late summer, or fall, as it has been cultivated to withstand heat, rain, cold, and dampness. 40-50 days to maturity.

Green Pac: Green Pac bok choy gets its name from its distinctive deep dark green oval leaves and pale green stems. It is especially well suited for harvesting as a baby bok choy. When allowed to mature to full size, Green Pac reaches heights of 10 inches tall. 48 days to maturity (21 days for baby bok choy). 

Joi Choi: Joi Choi is a versatile type of bok choy that has been bred to tolerate both hot and cold weather, and it is also slow to bolt, making it a versatile variety that is suitable for growing in a broad range of climates. It is a hybrid with white stems that contrast with the glossy dark green leaves and is valued for its juicy leaves with mild flavor that is similar to mustard greens. Joi Choi is known for maturing quickly, producing high yields,  and growing to large sizes, up to around 18 inches tall when finished growing. 45-55 days to maturity.

Li Ren Choi: Unlike most varieties of bok choy meant to be harvested as baby bok choy, Li Ren Choi creates heads that are proportionally shaped and completely filled out with dense, tightly packed leaves. Its small size saves space in the garden and matures quickly. Prized for its tender dark green leaves with pale green stems that have crisp texture and sweet flavor. This variety flourishes in chilly weather, so it can be sown repeatedly from late summer until the middle of autumn. In some areas, Li Ren Choi can even be grown through the Thanksgiving holiday season. 40-45 days to maturity (21-24 days for baby bok choy).

Mei Qing Choi: Mei Qing Choi is famous for being the first bok choy hybrid green stem dwarf species that is both resistant to bolting and tolerant of both hot and cold weather. Produces uniform, compact, vase-shaped heads with a thick, heavy base and broad oval leaves in a rich shade of green that are prized for their tenderness. This adaptable variety can be grown in spring or fall, and gardeners in cool areas can grow it in summer as well. 40-50 days to maturity.

Red Pac/Red Bok Choy: Instead of the usual green leaves, Red Pak bok choy has leaves that are dark reddish purple or burgundy in hue. Their pigment results in a mild flavor similar to that of mustard greens. Red Pak is best suited for harvesting as baby bok choy. 45 days to maturity (21 days for baby bok choy). 

Rosie: This hybrid variety creates vase-shaped heads packed with leaves that are bright strawberry red, with greenish red stems. Rosie grows to heights of up to 12 inches tall if allowed to mature to standard size, though it is also well suited for harvesting as baby bok choy. This species is just as beautiful as it is tasty, and it is sometimes used as a border plant in the garden. 45 days to maturity (21 for baby bok choy).

Win-Win: Win-Win produces miniature or full-sized bulky vase-shaped heads of green leaves on white stems that are slightly smaller with denser heads than those of the Joi Choi variety—around 10 to 12 inches tall. This species of bok choy is renowned for the excellent flavor of its leaves. 52 days to maturity.

Growing Conditions for Bok Choy

Bok choy performs best when the temperature is between 64 and 68 degrees Fahrenheit, although plants can survive in temperatures up to 95 degrees and down to 27 degrees. However, gardeners should be aware that temperatures in excess of 75 degrees will result in tipburn, while more than a week of temperatures that dip lower than 50 degrees will cause plants to flower and begin the bolting process when the weather warms up again. 

Some gardeners choose to delay planting until the weather is warmer to avoid the risk of bolting, although this delay means that bok choy plants will face some serious heat while they’re maturing. While there are heat-tolerant varieties available, experiencing hot weather while the head is forming will cause the bok choy to form heads that are less dense and leaves that are narrower than they would normally be.

Another way that gardeners can discourage bolting in bok choy when it’s planted as a spring crop is to choose a location for bok choy plants that offers partial shade, then make sure to keep the plants consistently hydrated. Baby bok choy is also less likely to bolt than standard sized bok choy because of the 10 to 14 fewer days required for baby bok choy to mature.

When days are short, the plant will focus its resources on growing the foliage we eat as a vegetable. Longer days will trigger the plant to focus instead on reproduction, triggering the growth of the flowering stalk. Asian greens with smaller leaves than bok choy do better than it does over the winter, but in USDA Hardiness Zones 4 to 7, bok choy may survive through the winter if it’s protected by growing under cover. However, once spring arrives, the plants will go to seed.

Choose an area in your garden for bok choy that offers full sun if possible, though the plants will tolerate partial shade if needed. At minimum, bok choy needs to get between three and five hours of sunlight each day to grow strong and healthy. Make sure the area where you plan to grow your bok choy has not been host to a Brassica crop (such as broccoli, Brussels sprouts, cabbage, cauliflower, rutabaga, or turnips) in the previous four years.

The plant prefers growing in sandy soil rich in nutrients that drains well but also retains moisture to keep it available for the plants. It will tolerate a pH level ranging from 5.5 to 7.5, but really thrives when the pH range is between 6.5 and 7.0. (If you aren’t sure of the pH level in your garden, refer to our article “How to Test pH in Your Soil.”

Prepare the ground where you plan to grow bok choy by amending the soil with compost or well-rotted manure and organic fertilizer. Choose a fertilizer that has a high value for all three of the numbers separated by hyphens, because bok choy is a heavy feeder that needs plenty of nitrogen, phosphorus, and potassium (the nutrients the three numbers represent). 

How to Plant Bok Choy

Four to five weeks before the last expected frost of the spring in your area, you can start your bok choy seeds indoors. (If you aren’t sure how to determine your last frost date, you can find out in our article How to Learn Your Last Frost Date or Freeze Date).

Don’t transplant your bok choy seedlings into the garden until the temperature is staying above 50 degrees Fahrenheit at night—and if the temperature falls below 50 degrees after you’ve transplanted your bok choy, cover the seedlings to protect them. If your young bok choy plants experience a prolonged period of chilly weather or a frost, they will think they’ve gone through the winter season and will respond by bolting.

If you prefer, instead of starting seeds indoors and transplanting them, you can wait until one or two weeks before the last frost date in your area to sow your bok choy seeds directly into the garden outdoors instead. The seeds germinate relatively quickly, usually in about four to eight days.

Seeds should be planted between a quarter of an inch and half an inch deep, with an inch of space between each plant. Once the seedlings are a few inches tall, thin them out to at least six inches apart if you’re growing full-sized bok choy instead of baby bok choy. For baby bok choy, thin to four inches apart. 

Care for Bok Choy

Make sure to keep the soil evenly moist as you wait for the seeds to germinate and sprout. Don’t allow the ground to try out while the seedlings are working to germinate. A layer of mulch spread over the surface of the soil where bok choy is growing can help the soil to retain moisture and also maintain a cooler temperature. You may also wish to set up floating row covers to help stave off some of the insects that tend to prey on bok choy plants so that you can harvest leaves that aren’t full of holes and ugly markings where insects have munched.

Succession planting bok choy seeds every few weeks will allow gardeners to have a longer harvest period, during which they’ll enjoy a continuous flow of bok choy from the garden. You’ll need to stop planting once hot weather arrives, but midsummer is a good time to start new plants to transfer into the garden in the fall.

Bok choy plants need lots and lots of water, especially if they’re planted in the fall. A period of drought when the plants are permitted to dry out can cause them to go to seed, so make sure to give your plants plenty of water on a regular basis, and never let the ground where they’re growing dry out between waterings.

Garden Pests and Diseases of Bok Choy

Although it’s a member of the Brassica family, bok choy does not usually struggle with the diseases that can plague other Brassicas. However, it does tend to face infestation from a variety of insect pests. Using floating row covers or otherwise protecting the crop can help prevent gardeners from facing these infestations. The pests and diseases listed below are ones that tend to impact bok choy crops in various regions.

Alternaria blight/Alternaria leaf spot: The hallmark of Alternaria are brown spots on leaves between half an inch to three quarters of an inch wide, which turn black in color as the fungus behind Alternaria begins to produce spores. Spots run together and merge as the disease progresses, discoloring entire leaves to yellow and brown or causing a scorched appearance. The disease strikes most often in June and July when temperatures are warm, in areas where dew forms in the morning, the humidity tends to be high, and the air remains stagnant without a breeze. The name “Alternaria leaf spot” and “Alternaria blight” are actually used to describe an entire group of fungal diseases caused by several types of closely related fungi.

Alternaria tends to be a problem in overcrowded gardens because it spreads via wind, water splashing, or is transmitted by gardening tools and equipment or the gardener’s hands and clothing. The fungi that cause Alternaria can survive over the winter on debris from infected plants, if it is left in the garden until the next season. Clean this debris along with any fallen leaves out of the garden frequently to prevent the disease, and also refrain from watering plants from above and splashing the foliage. You can also prevent Alternaria by setting plants up with plenty of space between them for air and sun to circulate. Quarantine and desroy any infected plants; they should not be eaten, fed to animals, or used in compost. Learn more about how to diagnose, prevent, and treat Alternaria in our article Dealing With Alternaria Blight.

Aphids (cabbage aphid, green peach aphid, potato aphid, turnip aphid): Although there are many different varieties of aphids that can vary in size and color, all of them are tiny, and all can be found on the underside of the leaves of infested plants. Aphids suck the moisture from the foliage of plants they are afflicting, so the plants show symptoms of distorted, withered, or misshapen leaves. You can treat to get rid of aphids with a homemade spray using one liter of warm water, four or five drops of dish soap, and a tablespoon of neem oil. Learn more in our article How to Spot and Get Rid of Aphids with Organic Methods.

Bacterial soft rot: The name “bacterial soft rot” is used to refer to an entire group of diseases, which combined result in more crop loss across the globe than any other plant disease. Bacterial soft rot results in damage to the succulent parts of crops in nearly every plant family, such as bulbs, fruits, stems, and tubers. The woody parts of plants are not normally affected. The disease can spread to all kinds of cruciferous vegetables as well as carrots, cucumbers, melons, potatoes, pumpkins, squash, and tomatoes. The worst damage happens when temperatures are between 70 and 80 degrees Fahrenheit, especially when oxygen is scarce and the weather is wet. Damage can be most severe when plants are in need of calcium. Signs first show up as water-soaked areas that become sunken and soft as they enlarge. Underneath these spots on the surface, interior tissues also become discolored (ranging in hue anywhere from cream to black) and mushy in texture.

Soft rots are notorious for causing a strong unpleasant odor as they break down affected plant tissue. Several different bacteria cause bacterial soft rot, and they can enter plants through punctures or wounds that result from damage from gardening tools, insects, severe weather, or natural openings in the plants. The bacteria can then travel from plant to plant via means such as insects, contaminated gardening tools, or the movement of infected plant debris, water, or soil. There is no treatment for bacterial soft rot; impacted plants must be removed and discarded. They must not be buried or used in compost.

Cabbage looper/alfalfa looper: Cabbage loopers look like green caterpillars with a distinctive “looping” gait similar to that of the inchworm. They transform into brownish gray moths with white spots that, like the caterpillars, will eat holes in plant foliage. You can manage them by using floating row covers, picking off larvae manually and dunking them in soapy water to kill them, scraping eggs from the undersides of leaves and discarding them, or deploying parasitic wasps to prey on them.

The natural pest control botanical Bt (bacillus thuringiensis) is also an effective treatment against cabbage loopers. Learn more in our article How to Control Cabbage Loopers.

Damping off: Damping off is a disease that strikes when plants are at the seedling stage, causing the tiny plants to wither away and die or fail to germinate at all. The term describes a group of fungal diseases transmitted through the soil that are most prevalent with seeds started indoors. However, plants that are growing in the outdoor garden can also be affected if the soil they’re growing in gets too cold and wet.You can prevent damping off by using sterile potting soil and gardening tools and by not overwatering your seedlings and making sure they get adequate light and air circulation. Learn more in our article How to Prevent Damping Off [https://www.gardeningchannel.com/how-to-prevent-damping-off/].

Downy mildew: Downy mildew is a fungal blight that normally strikes when the weather is cold and wet. Affected plants will show fuzzy spores on the undersides of leaves in shades of gray, purple, or brown. They may also display stunted growth, contract other diseases, or drop their flowers and fruit. The spores behind downy mildew travel and spread via wind, insects, or splashing water. You can prevent downy mildew by keeping moisture managed and making sure it doesn’t get excessive in the garden, and you can treat it with an organic fungicide. Learn more in our article Identify, Prevent and Treat Garden Problems: Downy Mildew Fungal Disease.

Leafminers: Gardeners may see leafminers at any part of their life cycle: as eggs, the larvae that tunnel through plant foliage, or as the moths, beetles, and flies that the larvae eventually grow into. Plants that have been chomped on by leafminer larvae will have wiggly lines in the leaves, and the larvae may be visible at the end of the line as a dark spot. It’s important to catch a leafminer problem before it gets too severe, or you can lose entire harvests. You can fight leafminers with parasitic wasps that prey on the larvae. Learn more in our article How to Fight Leafminer Insects.

How to Harvest Bok Choy

When you’re growing bok choy to its standard size, expect a maturation period of between 40 and 60 days, depending on the variety you’re growing. Baby bok choy usually takes about three weeks (21 days) to mature so that it’s ready to be harvested. You should harvest bok choy when it has between 10 and 15 leaves. If you wait too late and the bok choy grows more than 15 leaves before you harvest the plant, the taste of the leaves will turn bitter.

You can treat bok choy as a “cut and come again” crop by cutting the plants off at about an inch above the ground. They will put out new leaves from the inch of foliage you left behind, and although the second round of leaves will never reach the same size as they did originally, their taste won’t suffer at all.

Bok Choy at the supermarket

How to Store Bok Choy

When you’ve just harvested a bok choy plant from the garden, you can keep it at room temperature for the first day or two. However, if you won’t be using it within two days, it’s better to store the bok choy in the refrigerator, where it will last for five days or longer.

If you need to store bok choy for longer than five days, your best option is to freeze it. After thoroughly washing the leaves, blanch them in boiling water for two minutes. Remove the leaves with a slotted spoon, and transfer them into an ice water bath, letting them soak for at least two minutes more. Then move the leaves to a colander or onto paper towels or dish towels to dry. 

Once the leaves have dried, divide them into the portion amount you will use when cooking. (Use whatever amount makes sense for your family, whether it’s one cup or two or three cups per portion.) Pack each portion into a freezer safe plastic zipper bag (removing as much air as you can) or into a plastic food storage container that’s made to be frozen, then place them in the deepest part of your freezer. The bok choy will stay good for five to six months in food storage containers or for 10 to 12 months in freezer safe zipper bags.

As you can tell, there’s a reason that bok choy has been cultivated for centuries. It’s a versatile crop that can be grown at several different times of year, as baby bok choy or standard sized bok choy, with red leaves or green, with white or green stems—the options and adaptations are almost endless, especially when you start learning about the various varieties of hybrid and heirloom bok choy that are available. When you start growing your own bok choy, you’ll see why this rewarding crop has such a long history, too. So why not plant some bok choy of your own in your garden?

Learn More About Bok Choy

https://cals.arizona.edu/crops/public/docs/AZbokchoy.pdf

https://edis.ifas.ufl.edu/hs1337

https://extension.umn.edu/vegetables/growing-chinese-cabbage-and-bok-choy

https://www.gardeningknowhow.com/edible/vegetables/bok-choy/planting-bok-choy.htm

http://www.gardening.cornell.edu/homegardening/scene0bdf.html

https://homeguides.sfgate.com/grow-bok-choy-indoors-68399.html

https://www.medibank.com.au/livebetter/be-magazine/healthy-kids/growing-bok-choy-from-scraps/

http://www.omafra.gov.on.ca/CropOp/en/spec_veg/brassicas/bokc.html

https://www.rhs.org.uk/advice/grow-your-own/vegetables/pak-choi

http://www.ucanr.org/blogs/blogcore/postdetail.cfm?postnum=28354

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