Kale microgreens

Kale is measured at 10 grams of seed per 1020 tray returning 11 ounces at first true leaf, which puts it within half an ounce of broccoli on yield while using less seed. The two crops are close to interchangeable in a tray, and this page says so rather than inventing a difference. What you are actually buying when you choose kale is Red Russian's purple stems and the word on the label.

There is a wrinkle underneath all of it. Kale is generally Brassica oleracea var. sabellica, but Johnny's own Red Russian page labels that particular seed Brassica napus, a different species. Red Russian is also the only kale anyone has put through a trial. So every published kale microgreen figure in existence, including the ones at the top of this page, comes from the cultivar whose botanical name does not match the crop it is sold as.

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

Kale microgreens are seedlings of kale, cut above the medium once the cotyledons are fully developed or the first true leaf begins to emerge. The trade sells at least six of them for microgreen use: Red Russian, Toscano, Bright Green Curly, KX-1, Unicorn, and a Kalefetti mix.

A correct tray is a short, even stand of two rounded mid-green cotyledons on fine light stems, roughly half an inch to two inches tall, cut clean above the medium. It should not look like miniature mature kale: no blue-green cast, no waxy coating, none of the crinkle. Cultivar changes the picture more here than on most crops. Red Russian carries bright purple on the stems and leaf margins and produces serrated first true leaves. Toscano is the exception in the other direction, the darkest green of the kales on light green stems.

It is confused with broccoli, and at cotyledon stage there is no honest way to tell them apart. The cotyledons and the fine light stems are near identical, and nothing opened for this page offers a reliable one-glance test. That is the truthful answer, and the practical consequences follow from it: either wait for the first true leaf, or keep the seed identity and label the tray. On Red Russian specifically the true leaf settles it, because it comes in serrated with bright purple margins and stem. That tell belongs to Red Russian, not to kale in general, so do not expect a green cultivar to announce itself the same way.

What it tastes like, and what to do with it

Mild and gently earthy, recognizably kale without the toughness or the bitterness the mature leaf can carry. Johnny's describes Red Russian as mild kale flavor and Toscano as mild and earthy. There is no heat in it at all.

That mildness is the whole use case. Kale microgreens are volume rather than accent: fold them through a salad, layer them into a sandwich, put them on an entree as a light garnish. They are tender enough to eat in quantity, which is the thing mature kale is not, and that contrast is worth more to a customer than any flavor note you could write.

It is the wrong choice when the plate wants heat, in which case radish or mustard does the job, and it is the wrong choice when someone wants the chew of mature kale, which no microgreen will give them.

The people who will not like it are the ones who do not like brassica flavor at all, even mild. That is a real group and there is nothing to be done about it. Nobody has run a consumer sensory study on kale microgreens, so how large that group is remains genuinely unknown.

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. Kale barely departs from it, and being honest about that is more useful than manufacturing deltas.

Ten grams per 1020, not twenty to thirty. Johnny's ran Red Russian in its 2017 trial at 10 g per tray, about three flats to the ounce of seed, and repeats the figure on the product page. Toscano's page lists 10.5 g. Kale seed runs about 146,600 seeds to the pound, so this is a fine-seeded crop and it should be sown by weight rather than by eye. Seed lower if you intend to grow past first true leaf, because a thinner stand has better airflow and depletes water and fertility more slowly. Do not raise the rate until a trial in your own system shows the stand stays healthy.

No soak, and no source says otherwise. The documented instruction is to broadcast dry, press firmly into the medium for contact, then cover lightly with mix or vermiculite, or use a humidity dome. Nothing opened for this page establishes a useful soak time or water temperature for kale seed. The federal seed-testing table does not prescribe one either.

Broadcast at an eighth to a quarter inch apart and press, do not bury. Bottom water or mist rather than watering overhead, because the crop is short and overhead flow splashes medium up into it.

Warm to germinate, then cool. Johnny's calls for 75°F at the medium until germination and 60°F after it, with 65 to 75°F ambient generally favorable, and warns that above 75°F germination can be inhibited and disease pressure rises. Virginia Tech's general microgreen target is 60 to 70°F.

The blackout is the honest gap on this page. Neither kale supplier page nor the yield trial gives a number of blackout days or a weight in pounds, which is a strange hole in the crop the category most often hands to beginners. What is documented is the signal rather than the number: uncover once the majority of seedlings have germinated, which across species generally falls between two and five days. Anyone quoting you a kale-specific blackout schedule is quoting a preference, and the growers on r/microgreens quoting one are being more useful than the literature, which is not something this directory gets to say often.

What goes wrong with kale specifically

The honest headline is that kale has no signature failure of its own. What it has is the general seedling disease complex, made likelier by the one thing this crop does do differently, which is grow densely at 10 g in a tray.

Before emergence: seed rot and a stand that never arrives. Pythium can begin at the root tips, and those seeds are not recoverable. You find out by counting gaps.

Just after emergence: damping-off. A water-soaked or darkened, pinched stem at or below the medium line, then toppling. Individual seedlings do not recover, so remove them and fix the cause, which is nearly always drainage or airflow rather than anything to do with kale.

Then: spread through a wet, crowded tray. More gaps, more collapse. Shared water and shared medium carry the pathogen, so a broadly affected food tray is a discard rather than a treatment problem. Pythium favors cool and wet; Rhizoctonia will work warmer and drier. Neither is a kale disease.

And the one that is about timing rather than disease. Kale's measured figures belong to a first-true-leaf cut. Johnny's notes that each day past that can materially change plant size and yield, and advises sowing lower if you intend to grow larger. You can see it coming: true leaves progressing well beyond the first, and the stand starting to crowd and shade itself. What nobody has measured is what that costs you in texture, flavor or saleability, so this page does not claim a penalty it cannot source.

A bad lot looks like technique. It presents as a low, patchy or delayed stand at a sowing weight you know is right, which is exactly what a watering mistake looks like. Test a retained sample before committing trays. Worth knowing that Johnny's trial excluded obvious poor-germination flats from its averages, which is precisely why a published average cannot certify a lot you just bought.

Nutrition, and what is actually established

There is no kale microgreen entry in USDA FoodData Central, checked 2026-08-08. The search returns a branded product, BRIGHTFRESH MICROGREENS MICRO KALE MIX, FDC ID 1549661, which is a mix and not a composition record for kale. It also returns mature raw kale entries, which are a different food at a different stage and are not a substitute.

The accessible kale-specific literature is one study, and it is more interesting than a marketing line would be. Zanzini and colleagues (2020) grew kale in trays and compared 15-day microgreens against 40-day baby leaves and 60-day adult plants, measuring carotenoids, minerals, phenolics and antioxidant capacity. The result runs in both directions: the microgreens and baby leaves carried higher micronutrient levels and higher phosphomolybdenum antioxidant capacity, while the adult kale carried higher phenolics and higher total carotenoids.

That is the useful finding, and it is the opposite of the claim in circulation. On the compounds this study measured, the mature leaf beat the microgreen on two of them. Anyone telling you kale microgreens are simply more nutritious than kale is not describing this study, and no other kale-specific composition source exists to describe instead. A fixed vitamin K or vitamin C figure, a multiple against mature kale, or the word superfood, are all unsupported here.

Which seed to buy

Two cultivars have real published detail behind them and the rest do not.

Red Russian is the default and the only one with trial numbers: medium-green serrated leaves, bright purple stems and margins, mild kale flavor, 10 g per tray, 13.5 days to first true leaf, and 11 oz average yield. Toscano is the visual opposite, the darkest green of the kales on light green stems, mild and earthy, listed at 10.5 g per tray and 13 days. Between them they cover the two looks a buyer might want.

Bright Green Curly, KX-1, Unicorn and the Kalefetti mix are all sold for microgreen use, and none of the opened listings gives a measured stem length, days to harvest or yield for any of them. Their mature-kale reputations do not transfer, so treat those four as untested rather than assuming the name tells you something.

Order seed sold explicitly for microgreens or food use, name the cultivar and the lot, and require untreated seed. SDSU Extension is direct about why: seed treatments may be present in the young shoots, and the shoots are what gets eaten. Organic is useful additional assurance and is not a substitute for a clean system. And specify the cultivar rather than accepting generic kale, because Red Russian's purple stem is the reason a buyer picks this crop over broccoli, and generic kale might arrive green.

Is it worth growing?

Yes, and the reason is narrower than the category pretends.

By the numbers kale and broccoli are close to the same crop. Kale uses 10 g against broccoli's 13, returns 11 oz against 11.5, and takes 13.5 days against 12.5. Nothing there is a reason to choose one over the other. What is a reason: Red Russian's purple stems, which broccoli cannot produce at any seed rate, and a label that says kale, which some buyers want specifically. If neither of those matters to your customer, broccoli is the cheaper tray and the honest recommendation.

It suits the beginner who wants a mild brassica on a short cycle, the market grower who now has a real 10 g and 11 oz benchmark to plan against rather than a guess, and the home grower who wants something to eat by the handful rather than a garnish. Choose something else if the buyer wants heat, if they want a crop that cuts twice, or if the pack needs a color no kale produces.

Its competition is broccoli first, on the mild green brassica slot, and then cabbage and kohlrabi in the same lane. Against radish and mustard it is not really competing on flavor at all, only for space on the rack.

A note on the numbers above

The correction here is the broccoli correction again. Twenty to thirty grams became a measured 10 g, and 5 to 8 oz became a measured 11. On both crops the published seed rate was two to three times too high and the published yield was understated by roughly a third to a half, in the same direction, for the same reason: the provisional numbers were written from general knowledge rather than from the one trial that measured them.

Three fields are blank on purpose, and the blackout one is the surprise. Nobody publishes how long a kale tray holds a good cut, nobody has measured hull retention on it either way, and, more oddly, no supplier page and no trial gives a blackout period or a tray weight for kale at all. That last gap sits on the crop this category most often recommends to a beginner. Blank here means no published figure exists, which is different from not applicable and different again from nobody having looked.

Days to harvest spans 8 to 15 because three sources measured different things. Johnny's trial averaged 13.5 days to first true leaf, its product page says 10 to 15, and Virginia Tech's crop table says 8 to 14 without stating a stage. Toscano's page says 13. They are not in conflict; they are answering slightly different questions, and only the trial figure carries a stated harvest stage.

One number on this page is a test protocol, not a growing instruction. The 68 to 86°F range is what the federal seed-testing table specifies for a standardized kale germination test, with a first count at three days and a final count at ten. It describes a laboratory procedure. It is not a recommendation for your rack, and it circulates as though it were.

That last table is the one nobody else can build, and it only became possible once four crops had been researched to the same standard with prices dated the same day. All four land within three and a half ounces of each other on yield, and they are nearly three times apart on what that yield costs in seed. Broccoli returns 14.5 oz per dollar of seed and Daikon radish returns 5.0. Radish earns its place on speed and on color, not on economics, and that is a conclusion no single-crop page could ever reach. Prices move, so the dollar figures are dated rather than permanent; the ranking is the durable part.

Sources

• Johnny's Selected Seeds, kale Red Russian organic microgreen seed - 10 g per 1020, 10 to 15 days, mild kale flavor, serrated leaves with purple stems and margins, 146,600 seeds per pound, dry sowing at an eighth to a quarter inch, 75°F then 60°F with 65 to 75°F ambient and the above-75°F warning, 5 to 10 days storage, the Brassica napus labeling, and the $48.50/lb price behind the cost calculation, listed 2026-08-08.
• Johnny's kale Toscano organic microgreen seed - 10.5 g per tray, 13 days to first true leaf, darkest green leaves on light green stems, mild and earthy.
• Johnny's microgreens yield trial results (PDF) - Red Russian at 10 g per 1020, 11 oz average, 13.5 days to first true leaf, about three flats per ounce of seed, and the rounding and variation caveats.
• Johnny's microgreens yield trial, method and discussion - the 2017 greenhouse method, at least three seedings per variety, exclusion of poor-germination flats, the advice to sow lower for larger plants, and the warning that one system's yields do not transfer.
• Johnny's microgreens, top picks for getting started - the kales listed among the explicit easy starting choices.
• Johnny's microgreen catalogue - Bright Green Curly, KX-1, Unicorn and Kalefetti sold for microgreen use with no measured figures published.
• Virginia Tech Extension SPES-756 (PDF) - kale as B. oleracea var. sabellica, the 8 to 14 day range, the 60 to 70°F general target, uncovering once most seedlings have germinated at typically two to five days, and damping-off as the leading disease concern.
• SDSU Extension, growing microgreens at home - salad, sandwich and garnish uses, about a week refrigerated in a bag or container, rinsing in cool water before eating, and why treated seed is unacceptable on a crop eaten as young shoots.
• Purdue Extension, grow microgreens at home - about a week unwashed in the refrigerator, washed just before eating.
• UC IPM, damping-off - Pythium and Rhizoctonia, Pythium often beginning at root tips, and the conditions each favors.
• UMN Extension, how to prevent seedling damping-off - the failure sequence and why a broadly affected tray is a discard.
• Oregon State Extension, high desert gardening newsletter, April 2025 (PDF) - the water test for root hairs against mold, and mold becoming more web-like when wetted.
• 7 CFR 201.58, federal seed-testing table - the standardized kale germination test at 20 to 30°C with a first count at three days and a final count at ten, and no presoak.
• Zanzini et al., 2020, kale at three growth stages - 15-day microgreens against 40-day baby leaves and 60-day adult plants, with microgreens higher in micronutrients and phosphomolybdenum antioxidant capacity while adult kale was higher in phenolics and total carotenoids.
• USDA FoodData Central - searched 2026-08-08, no single-ingredient kale microgreen record; FDC ID 1549661 is a branded micro kale mix, and mature raw kale entries are a different food.