Japanese Pantry
Komatsuna (Japanese Mustard Spinach): A Mild Leafy Green
小松菜（こまつな）
By the Aoi's Japanese School Lunch team · October 31, 2026 · 1 min read
What komatsuna is, how Aoi uses it in tuna onigiri, how it compares with spinach, and which greens to use if you can't find it.
In the video "How To Make Delicious Onigiri At Home," the first rice ball mixes tuna and komatsuna into rice. Komatsuna is a mild Japanese leafy green that shows up often in Japanese school lunches; more than 40 recipes on this site use it.
What is komatsuna?
- A leafy green from the cabbage family. In English it is often called Japanese mustard spinach, but it isn't a kind of spinach. The leaves are tender and mild, and the stems are crisp.
- A good source of calcium. In Japan's official food composition tables, 100 g of raw komatsuna leaves has 170 mg of calcium and 2.8 mg of iron. Raw spinach has 49 mg and 2.0 mg.
- Quick to cook. A short boil is all it needs.
How it's used in the video
- 0:27 The first onigiri is tuna and komatsuna.
- 2:46 The komatsuna is cut into pieces, boiled briefly, cooled under running water and squeezed dry, then mixed into the cooked tuna rice. Aoi says it adds color and nutrition, and that a quick boil keeps it bright green.
Tips
- Wash the stems well. Soil tends to collect where the stems meet.
- Squeeze out the water after boiling so the rice doesn't turn soggy.
Can't find it?
- Try Asian grocery stores and farmers' markets. It may be labeled "komatsuna" or "Japanese mustard spinach."
- Use another leafy green. In the video, Aoi says other leafy greens work too. Spinach or bok choy are good choices.
The other Japanese items in this video: aburaage, the drop lid and Japanese rice vinegar.
Related recipes
- Tuna Nameshi (Rice with Greens): the tuna and komatsuna rice from the video
- Komatsuna Nibitashi (Simmered Greens in Dashi)
- Miso Soup with Komatsuna and Aburaage
- Sumashijiru (Clear Soup with Komatsuna and Tofu)
