Growing Tatsoi, The Spoon-Shaped Mustard

Are you looking for a cool weather brassica that is as versatile as spinach, but keeps longer? Look no further than growing tatsoi. Packed with nutrients and easy to cultivate, tatsoi (Brassica rapa) is an Asian green that is cooked like bok choy. Tatsoi has origins in China. It is structured like bok choy but is smaller and slightly more bitter. 

At the end of winter or in the fall, it’s a poor time to grow flowers or warm weather lovers like okra, tomatoes, and peppers. So, why not try an Asian green like tatsoi? Growing tatsoi is easy! Sow one crop in spring, and find that another can be grown in fall. Pack your meals full of nutritious greens, raw or cooked. 

Tatsoi growing practices are easy. Cold-hardy and nutritional, this brassica needs just a little room to grow. Rosettes fan out to less than 10 inches tall in most regions. Tatsoi hosts less pests and diseases than most brassicas, too. It has a structure like bok choy, but smaller. Adapt it like spinach to incorporate into dishes. Its mustard flavor fits into many different profiles.

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• Monterey BT Caterpillar Killer
• Bio Solution BB Fix Beauveria Bassiana Powder
• PyGanic Botanical Insecticide
• Garden Safe Slug & Snail Bait
• Southern Ag Liquid Copper Fungicide

Quick Care Guide

All About Tatsoi

Tatsoi’s taxonomic name is Brassica rapa subsp. narinosa or Brassica rapa var. rosularis. It has many common names: tatsoi, tat choy, spoon mustard (due to its spoon shaped leaves), Chinese flat cabbage, broadbeak mustard, spinach mustard, wu ta cai in China, and tasai in Japan. It has been consumed and grown in Japan since 500 AD.

Tatsoi has convex spoon shaped leaves. You’ll find tatsoi growing in rosette formation, just as other members of the asian green family do. But tatsoi has smaller, 3 inch leaves and hugs close to the ground. It does not grow more than 10 inches tall to 12 inches tall in warmer climates and it grows 6 inch tall plants in cooler climates. Plants spread to 12 inches wide like other asian greens. 

Tatsoi leaves are dark green. Leaf stalks are small and white to pale green. If left to bolt, small yellow flowers with four petals arranged in a cross shape bloom from a central stem. All parts of tatsoi are edible. 

Tatsoi is grown biennially in temperate weather climates. Best planting times are in late winter or early spring, and late summer or early fall. Like other brassicas, consume leaves throughout the season before flowering. Harvest in just one and a half months. That’s quick compared to the 5-10 month growing time of broccoli or cauliflower.      

Cook rosette leaves into dishes like stir fries and soups. Serve it wilted, braised, or lightly fried as a side dish. Eat the whole plant — flowers and all — raw in salads, especially with baby greens. It’s great food medicine, too. Growing tatsoi will give you and your garden an excellent source of vitamins C, A, K, carotenoids, calcium, potassium, and folate.  

Planting Tatsoi

Sow seed outdoors two weeks before the last frost, or at the start of fall six weeks before the first frost. Avoid planting seeds or seedlings in late spring and summer. Tatsoi is not suited for warm conditions. It thrives in the cool late spring. Once summer hits, your first round of crops is done. Heat causes bolting and flowering, which makes tatsoi bitter in flavor. Harvest in spring, and grow another set of crops in the beginning of fall up to winter for a second fall harvest. 

Find a full sun to partial shade, area of your garden to plant. Tatsoi prefers well-drained, well-worked, loamy or sandy soils rich in nitrogen. It thrives outdoors in raised beds or in prepared ground soil. If gardening in-ground or in a raised bed is not an option, no problem. It will do well in carefully placed containers indoors and outdoors. If you have to grow indoors, find a south-facing window with plenty of space to place your container. 

To sow seed, amend unprepared soil with compost at an average depth of 10 inches. Seeds prefer 50 to 80 degrees to germinate. Create rows ½ to ¼ inches deep, spaced 18 to 24 inches apart. Tatsoi grows outward in a radial fashion, so ensure there aren’t other plants crowded out in that process. Drop seeds in the trench at 1 to 2 inches apart. Seed germination rates are high at 75%, so drop 2-3 per spot. As seedlings mature, thin them to 6 to 8 inches apart. This gives plants plenty of room to grow. Starts mature in 6 weeks.

Plant seedlings in the same temperature conditions you would for seeds but a couple of weeks later, with temperatures between 50 and 80 degrees. Grow tatsoi starts 6 to 8 inches apart, and harvest when leaves are mature — throughout the season until the flowering stage. Starts reach harvest maturity at about 3 weeks.   

Care

This plant is easy to care for. Meet tatsoi’s foundational requirements and maintain a healthy and long harvest. 

Sun and Temperature

Tatsoi, Brassica rapa grows in full to partial sun (at least 3 hours per day up to 5 hours). A full light-only location is ok if rows are covered with shade cloth. Shade cloth not only protects leaf tissue, but it also keeps out insects that might enjoy eating your plants. 

Tatsoi thrives in USDA hardiness zones 4 through 7, which provide enough cool weather, but not too much heat, which causes flowering. Seeds and starts prefer 50 to 80 degrees, and mature plants thrive at 60 to 70 degrees. But you can grow tatsoi in areas near these zones with extra care. 

A little frost is not a problem for tatsoi growing. It’s optimal to sow seed near the last frost. Harvests occur at lows of 15 degrees Fahrenheit. Once heat exceeds 80 degrees, tatsoi bolts. Then the growing season is over, and you can collect seeds. Alternatively, if conditions are too cold, leaves take on damage and wilt. 

Water and Humidity

These plants like generous amounts of water, up to 1 inch per week. Keep soil moist, but not drenched. Water tatsoi plants daily in the morning before ultraviolet rays are at their peak. Watering at this time prevents overheated soil temps which damage cold-loving Asian greens. 

Since all brassicas are prone to mildews, use a soaker hose or drip irrigation to water at the base of the plant for root absorption. Avoid wetting the leaves if at all possible. Watering may not be necessary if heavy rains or blanketed snow occurred recently. 

Soil

Grow tatsoi plants in sandy, loamy soils with good drainage. If soil is poor, prepare the area with compost up to 12 inches below the ground’s surface. Tatsoi plants cannot thrive in poor, clay-rich soils, so use a pH tester to ensure levels are at 6.0 to 7.5. Ideally, they prefer a pH of 6.5 to 7.0. 

Fertilizing

Prepare soil ahead of time (before you plant tatsoi, 3-6 weeks before the last frost) with nitrogen-rich addendums, like chicken manure compost, rabbit pellet compost, or coffee grounds. These provide a slow release of nutrition throughout the season. For subsequent applications, a reliable full spectrum fertilizer gives your tatsoi plants a boost. Look for balanced fertilizers that have a low NPK ratio. Fertilize tatsoi plants once per week at dusk in temperate times of the year with liquid fertilizers, or per manufacturer’s recommendations for granular slow-release fertilizer. 

Never fertilize plants in freezing temperatures or close to the last frost when they are in a stressed state. In this same vein, do not fertilize a sick plant. In these sensitive times, plants get burnt and damaged by fertilizers. For liquid applications, an initial soil soak is appropriate once the plant is established. In subsequent weeks, apply a lighter foliar spray. Space fertilization far enough apart to prevent malnourishment.

Pruning

Remove damaged or browning foliage from the rosette as they appear. Check daily to ensure damage to tatsoi is not related to fungal or insect pests. As tatsoi plants bolt in warm weather, remove any flowers and add them to a salad or eat them raw. Bolts are a sign the life cycle is completing. However, leaves can still be harvested up until the season is over if tatsoi bolts. The mustard flavor of tatsoi decreases into bitterness at the point of flowering. 

Propagation

Since tatsoi is biennial, the best mode of propagation is by seeds. Tatsoi’s life cycles aren’t long. Therefore, propagation by division is impossible. As summer or late winter draws near, let tatsoi bolt and flower. Shake flowering stems to release seeds, and gather them for the next season.

Harvesting and Storing

Harvesting tatsoi is easy! Begin doing so in 30-45 days. Although delicate and difficult to keep for long periods without much process, you can enjoy all parts of the plant throughout the season. 

Harvesting

When leaflets are at a 2-3 inch length, it’s ready to be harvested. Snap off fronds from outer edges or cut them off with clean garden shears. Let inner leaves remain to prolong the life cycle of your tatsoi. That way you’ll have greens throughout the growing season. Cut entire heads at the base and remove them at the end of the season. 

In heat, tatsoi bolts and flowers. Keep tatsoi from veering into the bitter realm at this stage by snapping off flowering heads just below the growth point of the first set of leaves. Again, all parts of the plant are edible, so eat those flowering heads in a salad or wilted as a side to your favorite protein. 

Storing

Store tatsoi the same way you would bok choy, in a plastic bag or damp towel in the refrigerator for up to one week. Due to their sensitive tissue, these gentle greens don’t do as well in the freezer as their brassica friends kale and collards. Dehydrate tatsoi at 140 degrees for 15 hours and store in a dark, dry place. Use dry pieces in salads or eat them as you would chips. 

Troubleshooting

Tatsoi becomes diseased if it is grown in unsuitable conditions. Give tatsoi what it needs, and it will thrive.

Growing Problems

Growth diminishes when seedlings are too warm. More mature plants bolt in higher temperatures. Intense cold below 15 degrees stunts plants and causes cold damage. 

Leaf browning could be an indication the soil content is not suited for growing tatsoi. If this is the case, it’s possible to save your tatsoi plant by digging a small trench in a circle around the base and filling that trench with nitrogen-rich compost. 

Tatsoi will wilt and brown if it does not receive enough water. Provide enough water to keep the soil moist, and check soil dampness daily. If soil is dry up to a 2-3 inch depth, add water. Water in the morning before the soil is warmed by the sun. 

Pests

Search your garden regularly for pests like slugs, cabbage worms, and flea beetles — the most common pests for tatsoi. Provide row cover to keep them off the tatsoi rosette. If that’s not an option, here are some other ways to contend, and make the flavor of these greens last throughout the season. 

Add washed and ground eggshells to the soil surface for slug issues. This method can even be applied proactively before planting seeds or starts. Slugs dislike the texture of eggshells. Commercial options for slug treatments include wool pellets and bait. Search your garden and handpick slugs for removal. This is the most effective method of pest control for slugs. Provide slugs with a trap crop of greens you don’t mind giving up. Plant these in rows around your tatsoi, or try a beer trap that kills them via alcohol poisoning. 

Cabbage worms are another common tatsoi pest. These feed off leafy greens to reach the pupation stage and eventually become moths, which do more of the same. Removed worms by hand, or plant moth decoys in the garden. BT, Bacillus thuringiensis, is an effective treatment. 

If you notice little round holes in the leaves of your tatsoi plant during your garden search, this is most likely flea beetle damage. Flea beetles are members of the leaf beetle family in the Altica genus. They can devastate leafy greens. Not only do adult beetles eat tatsoi, but they also reproduce below ground. Baby beetles hatch and consume roots to survive. 

Trap crops are not an option, as infestations spread into other areas. Instead, apply organic pesticides. Treat soil with diatomaceous earth. Beauvaria bassiana is a commercial fungal pesticide that when consumed liquefies their insides. Dilute before application, and do so at dusk as the sunlight kills spores. Apply pyrethrins daily if things get out of hand. 

Diseases

Clubroot (or Plasmodiophora brassicae) is a fungal disease that affects all brassicas in certain conditions. Plants infected with clubroot deform and crack. Eventually, they are unable to absorb nutrients at the root level. The only possible solution at later stages is to pull the entire plant and treat the soil. Ensure the pH level of the soil is optimal (6.5-7.0 for tatsoi) before growing tatsoi. Avoid pH levels of 7.2 in your garden to prevent clubroot. 

Powdery mildew presents as round white spots and occurs on tatsoi for many reasons. It proliferates from watering above your plants rather than at the base with a soaker hose or drip line. For the same reason, overcrowding causes powdery mildew. Treat plants by removing damaged parts, and thin over-crowders.

Poor drainage and overapplication of foliar fertilizers cause powdery mildew as well. There are fungicidal treatments available. These come in spray form and do not need to be diluted. Many organic options are safe for human consumption. Apply these up to one day before harvest. 

Downy mildew, although similar in name to powdery mildew, is not a fungal pest, but a parasitic algae from the Peronospora or Plasmopara genus. Leaves infected with downy mildew yellow and wilt rather than turning white. Downy mildew manifests near the base of a plant. Both mildews present in the same conditions: too much moisture in persistent cooler temps. 

Check for mildews when rains are heavy and the climate is cooler. Copper fungicide applications treat outbreaks as long as they are accompanied by proper garden hygiene. Even though downy mildew is not fungal the copper eliminates algae.

Frequently Asked Questions

Q: How long does tatsoi take to grow?

A: Tatsoi grows from seed to full maturity in 45 days. Starts mature in 20-25 days.  

Q: Can you eat tatsoi raw?

A: Yes! Eat tatsoi raw or cooked. It is a lovely addition to salad mixes, especially baby greens. 

Q: Can tatsoi grow in shade?

A: Tatsoi prefers partial shade, but full shade will stunt plant growth. Ensure tatsoi has at least 3-5 hours of full sun per day. Too much more causes tatsoi to bolt and lose flavor over time.