Komatsuna microgreens

Every entry in this directory eventually reaches the same unanswerable question: should you have left it another two days? Holding a tray longer adds weight and changes the crop, and almost nobody has measured both halves of that on the same plants.

On komatsuna somebody did. A controlled study grew it and weighed it at first true leaf and again at second true leaf, and got 2.34 kg per square meter against 2.95. That is 26 percent more fresh weight for one more leaf stage, from the same seed, in the same trays, under the same lights.

Set against that, the crop's own suppliers say the flavor intensifies as the leaves darken and the tray moves toward baby leaf. So the trade is legible for once: about a quarter more weight, for a product that tastes more strongly of mustard and is further from the tender thing that was ordered. Which side of that you want depends on whether you are selling by weight or by tenderness, and this is the only page here that can put a number on the first half.

What it is, and how to tell you grew it right

Komatsuna is Brassica rapa var. perviridis, sold in English as Japanese mustard spinach and often as Tendergreen. It is the same species as turnip, pak choi, mizuna and tatsoi, and a different variety of it, which is why it looks and behaves like all of them in a tray.

Two forms are genuinely sold: Komatsuna Green, with green-white stems and green leaves, and Komatsuna Red, with green leaves carrying red and purple highlights, usually in the leaves and veins rather than as a solid red stem. That is a real pigment distinction and not relabeling.

A correct tray is an even carpet of slender pale green to white stems with paired broad cotyledons, around two to three inches, over a fine white root mat at the medium. Growth climbing the stems is not part of it.

Identification at cotyledon stage is not possible and this page will not pretend otherwise. Komatsuna, pak choi, mizuna, tatsoi and generic mustard are all confusable, and no source opened here establishes a visual tell between them at that stage. The useful difference arrives at true leaf: komatsuna's is broad and spoon-shaped or oval, where mizuna develops conspicuously divided and fringed leaves. Before that, the seed label is the identification.

What it tastes like, and what to do with it

Mild, slightly sweet mustard-spinach with a gentle peppery bite. It is not hot the way a sharp mustard is, and a Red komatsuna supplier positions it specifically as suiting palates that find mustard too strong.

Its flavor is not fixed, and that is unusual enough to plan around. Suppliers report it intensifies as the leaves darken and develop, which is the same clock the yield section above is measuring from the other end. A day-10 cut and a day-14 cut are meaningfully different products, and neither is wrong.

Use it where soft leaf volume and a restrained brassica bite help: a rice or noodle bowl with soy, sesame and ginger, egg on toast, an avocado and cucumber sandwich, or a handful dropped onto soup at the end. It is a poor choice when the plate wants real heat, where radish or arugula belongs, or when it wants the crunch of pea shoots.

Who will not like it: people who dislike mustard-family bitterness or a sulfurous brassica aroma, and that dislike gets stronger the longer the tray is held.

Growing it: only what differs from the standard method

Everything general about trays, medium, light and watering is on the standard tray method for growing microgreens. Komatsuna's deltas are genuinely few, and saying so is more useful than inventing some.

Do not soak. Two crop-specific suppliers say so outright. At roughly 400 seeds per gram this seed is small but not dust, and wet seed clumps rather than spreading.

Sow evenly on a level bed and press for contact, do not bury. Level distribution matters more than depth here. A lumpy sow becomes a lumpy stand, and the crop is short enough that it never grows out of it.

Cover for two to four days, three being the target. This is a short blackout by the standards of this directory, where several brassicas take four to seven. Use only enough weight to keep seed and medium in contact; no komatsuna-specific weight has ever been published. Uncover when most seedlings have emerged and are pushing the cover, before the stems elongate and start trapping moisture.

Then bottom water and give it air. Nothing establishes that komatsuna wants more or less light, water, airflow or blackout than a default brassica tray, and this page will not manufacture a difference. The general daily light integral target of 9 to 16 is a baseline, not a komatsuna prescription.

Hold it at 64 to 75°F. A supplier reports poor germination below about 54°F and heat stress above about 77°F. Those are supplier thresholds rather than an experiment, but the shape is the usual cool-season brassica one.

What goes wrong with komatsuna specifically

First, patchy emergence, in the first two to three days. Bare zones from uneven contact or a surface that dried. On a crop this fast there is no recovery to an even market tray: the gaps are still gaps at harvest. Fix the sowing, not the tray.

Then, elongated pale stems. The cover stayed on too long. Get it into light immediately, and it will green up, but severe lodging does not straighten.

Then, damping-off. Water-soaked or pinched stems at or below the medium line with seedlings collapsing. Pythium can begin at the root tips and Rhizoctonia rots at the line. Discard rather than harvest.

And the root-hair confusion, which on this crop has the ordinary answer. Normal root hairs are bright white, confined to the roots at the medium, and become less conspicuous with moisture. Mold spreads as a web across medium and tissue, persists, smells off, and travels with collapse. Unlike the mucilaginous crops in this directory, komatsuna adds nothing that muddies that test, so use it.

Late, a different crop rather than a spoiled one. Darker, more developed leaves and stronger flavor, moving toward baby leaf. The signal is true leaves expanding past whichever stage you were aiming at. That is a decision rather than a failure, and the numbers section below is the place it gets priced.

Nutrition, and what is actually established

There is no USDA record for komatsuna microgreens, and mature komatsuna values are a different food.

One controlled study has measured this crop properly, and it is unusually thorough: fresh and dry yield, dry matter, color, eleven minerals, carotenoids, volatiles, anthocyanins and polyphenols, chlorophyll, ascorbate and antioxidant capacity, all at both first and second true leaf. Komatsuna came out highest along with pak choi for phosphorus and potassium in that comparison. It used a red-pigmented genotype in controlled chambers, so it describes those plants under those conditions rather than a retail nutrition label.

What is not supported is the marketing you will meet: that komatsuna microgreens are packed with vitamins A, C and K, that they prevent cancer or diabetes, or that they carry some quantified high calcium value. No USDA entry and no crop-specific human study backs any of it. The study above measured composition and in-vitro antioxidant capacity, which is a statement about chemistry and not about people.

Which seed to buy

Two forms are verified, Komatsuna Green and Komatsuna Red, and no controlled comparison establishes a difference between them in stem length, tenderness, days or yield. Choose on appearance. Ask for seed sold expressly for microgreens or sprouting, untreated and food-use, with lot and germination information; one supplier publishes an 80 percent minimum germination, which is the shape of answer to expect.

That is roughly 138 times the bulk price, and it beats endive's 85x for the widest gap on this site. The mechanism is the same one endive found: the garden shelf sells this species in packets counted for a vegetable patch, and a microgreen tray eats a packet at a time.

The difference, and it is good news, is that on komatsuna the bulk bag actually exists. Endive had no five-pound option a home grower could reach. Here there is a one-pound bag at $21.24, explicitly sold for microgreens, which sows somewhere between twenty and forty-five trays depending on whose rate you follow. Buy the pound. The named F1 hybrids in the gram packets, Green Boy and Summer Fest, are bred for field and greenhouse leaf production, and nothing establishes that either does anything different in a tray.

A bad lot shows as slow patchy emergence or weak seedlings, and on an eight to twelve day crop those gaps cannot fill before harvest. The loss is the whole tray's media, labor and rack time rather than the seed, which at bulk is under a dollar.

Is it worth growing?

Yes for a beginner, and yes for a home grower who wants something with more character than broccoli and less heat than radish. It is fast, it needs no soak, the blackout is short, and at bulk prices the seed is cheap.

For a market grower the honest answer is: trial it yourself first. Komatsuna is absent from the trade's 29-variety yield trial, so there is no 1020 benchmark measured the way broccoli's and kale's were, and the figures on this page come from a controlled study in trays a fifth the size of yours. That is better than nothing and it is not the same thing.

Its competition is the rest of the Asian brassica bench, pak choi, mizuna and tatsoi, all of them the same species, all similar in a tray. Pak choi wins on being better known to buyers, mizuna wins when the plate wants that fringed leaf, radish and arugula win when heat is the point. Komatsuna wins on broad tender leaf volume with a bite that stays polite, and it is the one to reach for when a customer likes the idea of mustard greens more than they like actual mustard.

A note on the numbers above

Komatsuna is the first crop in this table whose tray-day is blank for a NEW reason. Every other blank in that column is a missing yield. Here the yield exists and is measured; what is missing is the day count that goes with it. The study weighed the crop at leaf STAGES and never published days-to-stage, and the suppliers who publish days never state a stage. Pairing a supplier's day 10 with the study's first-true-leaf weight would look like a calculation and would actually be an assumption, so the column stays empty and says why.

The yield is an area conversion and the trays were small. 14 by 19 centimeters is about a fifth of a 1020, and small trays are more affected by edge effects than large ones. This is the same treatment fennel and spinach get and it carries the same warning: it is the only measurement in existence for this crop, and it is not a weighed 1020.

The seed rate is the interesting corroboration. The study's 70,000 seeds per square meter converts to about 22.6 g per 1020, which is close to MP Seeds' 24 g and roughly double Bootstrap Farmer's 10 to 15. A controlled study and a supplier arriving independently at the same density is worth more than either alone, and it means the twofold disagreement in the spec block is not a coin toss: the high end has support the low end does not.

And the cost figure is new work rather than dossier work. The research for this crop could not price it, because the one supplier it opened showed a price that was not tied to any of its three pack sizes. Checking the seed shelf directly turned up a named 1 lb bag at $21.24 sold for microgreens, which is what makes the value-per-dollar column possible at all.

A blank means nobody has published that figure. Every crop here has a full research file; where no measured number exists this site leaves the cell empty rather than repeating an estimate. How the numbers work

All 61 crops, sortable, on the microgreen comparison.

Komatsuna sits between the two halves of that table on purpose. It has more figures than anything below it and one fewer than everything above it, and the missing one is a day count rather than a weight. If somebody publishes days-to-first-true-leaf for this crop, it moves up into the ranked half at roughly 1.0 ounce per tray-day on a ten-day cut, which would put it near the top. That is a real number waiting on one small piece of reporting.

Sources

• Shared source note, added 2026-08-09: this same study supplies the pak choi entry's research figures. The two pages are not independent of each other, and pak choi's numbers are corroborated by Johnny's separate trial rather than by this page. On pak choi the study's area-converted yield lands within 4 to 13 percent of two measured 1020s, which is the only check this directory has on the conversion it uses here.
• Comparative study of Brassica microgreens at two harvest stages (PDF) - the controlled study behind this page's yield: 2.34 ± 0.05 kg/m2 at first true leaf and 2.95 ± 0.09 at second, n=3, 70,000 seeds/m2 in 14 by 19 cm peat trays, 24°C dark germination then 24/18°C, plus the mineral, carotenoid, volatile, chlorophyll, ascorbate and antioxidant measurements and the phosphorus and potassium finding.
• Bootstrap Farmer, microgreen cheat sheet - 8 to 12 days with an ideal of day 10, 10 to 15 g per 1020, and 3 to 5 blackout days.
• Golinucci, Komatsuna Green microgreens - Brassica rapa var. perviridis, about 400 seeds per gram, no presoak, 2 to 4 dark days, 10 to 12 days total, the green versus red distinction, and an 80 percent minimum germination spec.
• MP Seeds, Komatsuna Red microgreens - 24 g per 10 by 20 tray, 10 to 12 days, light green stems with green to purple leaves, and the positioning for palates that find mustard too strong.
• Mumm's Sprouting Seeds, komatsuna - no presoak, the mild slightly sweet mustard-spinach description, flavor intensifying as leaves darken, and the instruction to harvest dry and dry before sealing.
• Micropod, komatsuna microgreen seeds - the 64 to 75°F ideal, poor germination below 54°F, heat stress above 77°F, and the raw culinary uses.
• Kings Seeds, Komatsuna Red Leaf microgreen - the red leaf form and surface sowing.
• Johnny's microgreens yield trial, method and discussion - the absence of komatsuna from the 29 varieties tested, and the warning that one system's yields do not transfer.
• University of Maryland Extension, growing microgreens and baby greens indoors - the standard tray method the deltas above are measured against.
• Virginia Tech Extension SPES-756 (PDF) - the general 60 to 70°F microgreen range, the 9 to 16 daily light integral baseline, and storage at or below 41°F.
• UC IPM, damping-off - Pythium and Rhizoctonia, root-tip onset, and damp conditions favouring disease.
• USDA FoodData Central - no komatsuna microgreen record.