Chinese flat cabbage (Brassica chinensis) or Tah Tsai lettuce

How to Grow Tatsoi

Tatsoi is a cool-season crop grown for its delicious leaves that can be eaten fresh in salads or cooked in stir fries or lightly steamed.

Sowing 

Because Tatsoi is a cool-season crop it should be sown in early spring, autumn and even in the winter if grown under cover. When growing Tatsoi in your Harvst it is important not to keep the tray too warm, temperatures greater than 24°C will cause it to bolt, flower, and set seed. As bolting equals the end of harvest, keep well below the limit. The seeds tend to germinate really quickly, usually within 4-8 days. 

Tatsoi is fairly easy to grow from seed and can be direct sown or transplanted later. It is a perfect crop to sow in your Harvst as it can stay in there till it matures or be transplanted outside. 

Fill a tray with compost and water it. Sow the seeds about 5cm apart (or closer if transplanting early) and sprinkle 0.5cm of compost on top. Press down slightly to make sure that the seeds are in good contact with the compost. Carefully water again. 

Keep the soil evenly moist until seeds germinate because if they dry out they will most probably not germinate at all. This can be aided with a plastic dome over the tray but it is not a must.  However, as a general rule, the colder the soil the less moisture you need.

Plant care 

Keep the soil well watered throughout the growing season to avoid bolting and ensure good flavour. Also keep them fed throughout the growing season.

Growing options 

You can choose from one of the growing options below or do a combination of 2, 3 or 4! 

  1. Baby Leaves: Thin the seedlings to 7.5-10cm apart and then start harvesting directly from your tray when the leaves are big enough. If you pick one or two leaves of each plant from the outside, rather than the whole plant, it should keep on growing for a while and give you a few harvests! 
  2. Grow till maturity in your Harvst: When the seedlings have emerged, thin them to 15-20cm apart. This can be done by cutting the rejects with scissors (eat them in a salad!) or carefully using a stick/pencil to loosen the soil and lift the seedling up by its leaves and transplant to elsewhere. Make sure they are big enough to handle before you set out to do this. The compost will only have enough nutrients for a few weeks so you will have to feed the plants with an organic fertiliser throughout the growing season. 
  3. Plant outside: When the seedlings have developed their true set of leaves (not the first set appearing but the second set) they can be transplanted out into your garden. Space them 20cm apart. If you have problems with slugs, keep them in your Harvst a little longer till they’re about 10cm high. A bigger plant can resist a slug attack much better! When planting outside it is best to make sure that your soil is great before planting by adding well rotten manure or other organic material so that it’s full of nutrients for your plants. If your soil is not great you can feed the plants with an organic fertiliser throughout the growing season. When transplanting seedlings, ideally plant out early morning or evening and/or on an overcast day. Avoid planting at peak sun times or on windy days as this can cause sun or windburn which can lead to death! 
  4. Container Grown: Tatsoi grows well outside but as it is heat-sensitive, move containers into the shade on warm days and keep in mind that containers will warm quicker than garden soil in spring so keep it well watered. Also, keep in mind that the compost will only have enough nutrients for a few weeks so you will have to feed the plants with an organic fertiliser throughout the growing season. 

Harvesting 

Tatsoi leaves can be harvested as soon as they are big enough to eat and it is up to you if you like the small baby leaves or the larger ones!  Baby leaves are ready to harvest in 30 days, while semi-mature to full-sized rosettes take 45–75 days.  Leaves can be picked one at a time from the outside or a mature rosette can be harvested by cutting it at ground level. In any case, finish harvesting before the weather gets hot, as it will make the leaves tough and strongly flavoured and also make the plant bolt.

Watch out! 

Flea beetles are the biggest problem leaving the leaves covered in small holes and damaged areas turning brown. They tend to be more of a problem in spring than autumn but should in any case not be a problem in your Harvst! When planting out seedlings are particularly susceptible. The best solution is to grow plants under horticultural fleece and keep the soil moist. Also keep the plants well fed to help the crop outgrow the pest. Slugs can also be a problem when planting out and it may be better to keep them in your Harvst for longer.

Pro Tip

Tatsoi is very hardy when mature but exposure to cold temperatures in spring can trigger early bolting. However, in autumn exposure to light frost can improve Tatsoi’s flavour.

Nerdy facts

The botanical name is Brassica rapa and therefore belongs to the cabbage family. Tatsoi has been cultivated since 500 A.D in Japan.