Tatsoi: cultivation, care & use of leaf mustard

Tatsoi is also known in our country as leaf mustard because of its flavour and is visually very reminiscent of pak choi. The Asian vegetable may look exotic, but with the right knowledge it can be cultivated in a home vegetable garden without any problems.

Are you looking for a cold weather leafy vegetable that is as versatile as spinach, but lasts longer? Then we recommend the tatsoi (Brassica rapa convar. narinosa). Those who try to grow tatsoi will quickly discover that the Asian vegetable is unpretentious and easy to care for. We will teach you everything you need to know about cultivating and using exotic leaf mustard.

Tatsoi: origin and characteristics

So far, there is disagreement about the actual origin of tatsoi: some say that it originates from China, while others claim a Japanese origin. What is certain is that this plant, which originated in Asia, has been cultivated and consumed since around 500 AD. Today, it is cultivated in the warm temperate zones of Asia and even in the tropics. Just like its close relatives pak choi (Brassica rapa subsp. chinensis) and Chinese cabbage (Brassica rapa subsp. pekinensis), Tatsoi is increasingly finding its way into our cuisine and is now also cultivated in Europe and North America.

Tatsoi is also called spoon mustard or leaf mustard because of its small, spoon-shaped leaves. It is equally known as rosette pak choi. As its names suggest, tatsoi has a mild, mustard-like flavour, with the younger leaves resembling spinach (Spinacia oleracea). The hardy plant thrives in cool weather and can withstand temperatures as low as -26°C for short periods. Even snowfall is not a problem, which is why tatsoi is the ideal winter vegetable. In this process, tatsoi grows biennially, forming an inflorescence up to 1 m tall in the second year, and seed formation occurs.

This is how you can recognise tatsoi:

• Low-growing herbaceous plant that develops a taproot
• Spoon shaped, dark green, stalked leaves with white ribbing
• Leaves arranged in a densely growing rosette of leaves about 20 cm high
• Differs from spinach with its special taste
• Typical cruciferous flowers: about 1.5 cm in size, four-leaved, with intense yellow colouration

Growing tatsoi

Tatsoi can be sown directly or grown in advance on the windowsill. If you want to make the work a little easier, purchase pre-sprouted seedlings from the garden centre. For sowing, the right time is crucial because tatsoi shoots if grown too late in the spring or too early in the autumn.
Pre-cultivation for the spring and direct seeding for the autumn is recommended, which will provide plants for late harvest in the winter bed.

The right location for tatsoi

Tatsoi grows quickly and is ready for harvest after about 45 days, with baby leaves even ready four weeks after planting. Since it does not mind cooler temperatures, it can be sown in autumn for a second harvest. Although tatsoi is undemanding as far as temperatures are concerned, it requires a site sheltered from the wind and a well-drained, loose and humus-rich soil. The plant preferes full sun if it is sufficiently watered. Tatsoi’s water requirements are generally low – but it must not be allowed to dry out to avoid premature flowering.

How to plant tatsoi?

Nutrient-poor soils should be improved with some compost or manure before planting. Alternatively, fresh, high-quality soil can be worked into the soil. A nutrient-rich substrate such as our Plantura Organic Tomato & Vegetable Compost, which unlike many conventional vegetable soils is peat-free, is suitable for this purpose. Its increased potassium content meets the needs of cruciferous plants such as tatsoi.

• Prepare the planting site by digging the soil 15 to 30 cm deep to loosen it up.
• Take the seedlings and plant at a distance of 10-15 cm. It is essential to make sure that the heart of the plant is above ground – even after watering.
• Water plants and keep moist for the next few days.

Outdoor sowing

If you want to sow tatsoi directly outdoors, you can do it at two different times: either between mid-April and mid-May in spring. Alternatively, sowing is done between August and mid-October in late summer for an autumn and winter harvest into the new year. However, you should take into account that direct seeding extends the culture time by about a week. Plants sown later than mid-October remain in the bed through the winter and can be harvested the following year.

When direct seeding tatsoi requires a row spacing of about 30 cm. Tatsoi seeds are placed in a furrow and then covered with soil. Well watered, the seeds germinate after only four to eight days and can be thinned out as soon as the seedlings are about 10 cm tall. A distance of 10 to 15 cm between the specimens must be maintained. Fortunately, thinned out plants do not have to be disposed of, but can be used in a salad. If the tatsoi is grown as a baby leaf for lettuce, it is not necessary to separate the young plants.

Sowing indoors

From approximately mid-March, sowing and pre-cultivation of tatsoi can begin indoors. To do this, fill seeding trays with a high-quality, low-nutrient seedling soil such as our Plantura Organic Herb & Seedling Compost, as this will encourage vigorous root growth and promote healthy plant development. About 60 to 100 seeds are needed for an area of one square metre. After sowing, they should be covered with a little soil. Covering them with cling film with a few holes poked in it creates a kind of mini-greenhouse, which provides optimal conditions for germination. In a bright place, the seeds will germinate at 18 to 22 °C within four to eight days. The film can then be removed.

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Once the seedlings are around 10 inches tall and there is no fear of prolonged frost, acclimatise the tatsoi by placing the plants outdoors in a shaded area during the day. After another five to seven days, they are finally transplanted into the bed. Alternatively, tatsoi can be grown in a pot and then placed on a terrace or balcony.

Tip: The right temperature for seedlings and young plants is crucial, as they tend to shoot if it is too cold. Therefore, a temperature of 18 to 22 °C must be maintained during sprout development.

The most important care measures

Tatsoi requires a little care during growth – it particularly needs watering and fertilising. It is important to ensure a steady supply of water to the plants, otherwise drought damage will quickly occur. However, you should also pay attention to certain diseases and pests. These points are important in the care of the plant.

Watering tatsoi correctly

Make sure that the tatsoi plants do not dry out. On hot days, regular watering is essential for plant health. A mulch layer of lawn clippings, straw or bark mulch additionally reduces evaporation while suppressing the growth of wild weeds. Heat, as well as drought, may cause the plant to shoot and blossom. Flowering is then unavoidable, but to prevent a bitter taste the flowering heads are cut off just below the first leaf set. However, shooting can be prevented at an early stage through the right timing of sowing and appropriate care. As with pak choi, all parts of the plant are edible. The flowering heads can be eaten in a salad, for example, but taste more intense and somewhat bitter.

Tatsoi – like many cruciferous plants – is susceptible to mildew, so watering should only happen at the base of the plant. For this purpose, a soaker hose or drip irrigation is particularly well suited, or you can carefully water with a watering can or garden hose. Avoid wetting the leaves.

Fertilising tatsoi

During the short growing season, fertilisation of tatsoi is necessary. For this purpose, a nitrogen-rich fertiliser is suitable, which optimally covers the nutrient requirements during the intensive growth phase. A slow-release fertiliser in granular form releases nutrients into the soil over a longer period of time. The plants absorb this, which supports healthy leaf growth. For example, our Plantura All Purpose Plant Food promotes soil life as well as healthy plant development thanks to its high content of organic raw materials.

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A high-quality flower fertiliser is also suitable for pot culture and low nitrogen soil. For example, our Plantura Liquid Flower Food is significantly more nitrogen-rich than a liquid vegetable fertiliser and perfectly meets the needs of tatsoi.

Common diseases and pests

As already mentioned, mildew on tatsoi can become a problem due to incorrect watering. However, the fungal disease cabbage hernia is also a danger that should not be underestimated. Pests such as flea beetles but also leaf aphids, the small cabbage white butterfly and the cabbage fly can occur on tatsoi.

Harvesting and using leaf mustard

Those who grow tatsoi can look forward to the harvest soon after.

How to harvest tatsoi

Tatsoi is ready for harvest after 40 to 50 days, or baby leaf plants after just 30 to 35 days. Refrain from harvesting tatsoi during frost as damage occurs at the points of contact with the delicate leaves. To harvest, cut the heads about 1 cm above the ground with a sharp, clean knife. In mild weather, tatsoi may resprout if pruned a little higher up, allowing for another harvest. The second rosettes are smaller than the first, but equally aromatic.

Storing tatsoi

Tatsoi can be stored the same way as pak choi – in an airtight bag or wrapped in a damp towel, the cabbage will keep in the refrigerator for up to a week. Because of its fine tissue, tatsoi does not freeze as well as other plants in the brassica family, such as kale (Brassica oleracea var. sabellica) or rosewood (Brassica oleracea var. gemmifera).

Usage

Tatsoi can be used in many ways. The cabbage is wonderful as a pesto, salad, steamed, stir-fry, tatsoi vegetable and garnish for soups. It is an extremely versatile leafy vegetable that can be served raw or cooked. Tatsoi is used wherever you would use spinach or pak choi.

Discover the variety of Asian cabbage plants and also get to know the pak choi a little better in our special article.