How to Grow Red Cabbage Microgreens from Seed to Harvest

8 juin 2026

Back in December of 2019 we published a video called How to Grow Microgreens from Seed to Harvest. It was one of the first true, start-to-finish microgreen walkthroughs on YouTube, and it is the grow that took our channel from around 1,000 subscribers to 50,000 and set everything else in motion. Years later it is still our most-watched video of all time. We have never written the blog to go with it, so here it is.

The crop in that video is Red Acre cabbage, a beautiful purple brassica that is one of the most beginner-friendly microgreens you can grow. Below we walk the entire grow exactly the way we did it on camera, from measuring seed to weighing the final harvest, with the day-by-day detail that makes this method easy to repeat at home.

Dense tray of purple-stemmed microgreens lifted to show the leafy canopy and white root mat at On The Grow

Quick Answer: Growing Red Cabbage Microgreens

Red Acre cabbage microgreens are typically ready in about 8 to 12 days from seed to harvest. Seed a 10x20 tray with roughly 17 to 20 grams of seed onto a moist growing medium, blackout under weight for a few days, transition to light, bottom water once roots reach the reservoir, and harvest when the cotyledons are fully open and the first true leaves begin to show. In the grow below we took ours to day 13 on purpose to let it stretch a little taller for an easier harvest. The same method works for Mammoth Red Rock cabbage, another red cabbage variety we love.

What You'll Need

Seed: Red Acre cabbage seed. We get ours from True Leaf Market.
A way to measure seed: A kitchen scale is ideal. In the video we used tablespoons (about 2 tablespoons equals roughly 20 grams), but a scale lets you dial in your density and take real data.
A growing medium: We used coco coir in the original video. You can grab coco coir on Amazon. Soil and our reusable silicone grow medium both work for cabbage too.
Three trays: A solid bottom tray with no holes for the water reservoir, a tray with holes to hold your medium so roots can reach the water, and a second solid no-hole tray (a dark one is ideal) to flip on top for blackout. Our 10x20 shallow trays are the size we use most.
Something for weight: We use a paver of about 15 pounds during the weighted blackout phase for coco coir. For reusable mediums only use about 5 to 7 lbs.
A spray bottle on a fine mist setting for the blackout days.
Fertilizer (optional): We bottom water with Ocean Solution 2-0-3 once the tray is in light.
A sharp harvest tool: A harvest knife or a clean pair of scissors.

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Why Red Acre Cabbage Is a Great Beginner Crop

Red Acre cabbage is a brassica, the same easygoing family as broccoli, kale, and radish. It germinates reliably, grows predictably, and has a forgiving harvest window, so you are not stuck in a 12-hour scramble to cut it at the perfect moment. The flavor is mild and similar to other brassicas, and the deep purple color is what makes it stand out on a plate. If you are brand new to all of this, it pairs well with our beginner's guide to growing microgreens and our cornerstone broccoli microgreens guide.

While this video focuses on Red Acre cabbage, another favorite of ours is Mammoth Red Rock cabbage. It is just as beautiful, just as beginner-friendly, and it can be grown the exact same way using every step below. One difference worth knowing: in our space Red Acre can sometimes grow a little slower and a little shorter than Mammoth Red Rock. Because Mammoth Red Rock tends to be a touch more vigorous, we typically only run it about 3 to 4 days under weight followed by a single day of blackout, rather than the longer dark stretch we gave the Red Acre in this grow. So if you have Mammoth Red Rock seed on hand instead, follow the same process and just shorten the dark phase.

Step 1: Seeding the Tray

Start by measuring your seed. In the video we used about 21 grams for a single 10x20 tray. That worked, but it gave us a few late bloomers in the canopy, so we noted that next time we would dial it back to around 17 grams. For Red Acre cabbage, somewhere in the 17 to 20 gram range on a 10x20 is our sweet spot. Set your measured seed aside.

If you are using coco coir, break down the block with water first, then scoop it into your holed tray and spread it as level as you can. You do not want high spots and low spots, because uneven medium leads to uneven germination. Break up any big chunks as you go.

Red cabbage microgreens just germinating with pink radicles and fuzzy root hairs on a reusable silicone grow medium

Once your medium is level, spread the seed evenly across the surface. The goal is full, even coverage with seeds nearly touching but not piled in clumps. Dense clumps reduce airflow and invite problems later. After seeding, give the surface a good fine mist. This is most of the tray's water source for the first few days, so get it nice and saturated. If you want a deeper look at spreading technique and density, our common growing mistakes guide covers the most frequent slip-ups.

Step 2: The Weighted Blackout Phase

Set your seeded tray on top of the solid bottom tray. There is no water in that bottom reservoir yet, and there will not be until roots appear. Place the second solid tray upside down on top of the seeds, then add your weight. For coco coir, we use a paver of about 15 pounds. For reusable silicone we suggest 5 to 7 lbs. This is what we mean when we say a tray is "weighted." The weight encourages even germination and strong root contact with the medium.

We kept ours weighted for three days. Twice a day, lift the top tray, brush any stray seeds off it, give everything a light mist so it stays saturated, then re-cover and re-weight. Do not add water to the bottom tray during this phase. If you are growing Mammoth Red Rock instead, it tends to move a little faster, so we usually run it about 3 to 4 days under weight. If you want the full reasoning behind weighting, we ran a 4-tray test in our why microgreens need weight experiment.

Early red cabbage microgreens showing bright magenta stems and seed coats on a reusable silicone grow medium

Step 3: Switching to a Blackout Dome

After about three days weighted, the seeds have germinated and built enough strength that the weight has done its job. At that point we put the paver away and flip the top tray into a blackout dome, leaving it propped over the canopy without the heavy weight. This second stretch of darkness encourages the microgreens to reach up and grow a little taller, which makes for an easier harvest and a bit more product.

How long you dome depends on the variety. For Red Acre we ran three days under the dome in this grow because it can be a little slower and shorter and we wanted extra height. For the more vigorous Mammoth Red Rock, we usually only need a single day of blackout after the weight. During the dome days, keep misting the top lightly as needed, and start checking underneath for roots. Once you see roots reaching down, give the bottom of the medium a light mist so those roots do not dry out and turn brown. You want them to stay that healthy white color. We still are not bottom watering yet at this stage. For the full breakdown of when to move between these phases, see our weight vs. blackout timing guide.

Dense canopy of red cabbage microgreens with vivid purple stems and green-purple cotyledons grown on a reusable silicone grow medium

Step 4: Bringing It Into the Light

We ran three days weighted and three days under the blackout dome, which put us at day six. By then the canopy had reached the height we wanted, so it was time for light. Set the tray under your grow lights and the pale stems will start greening and showing their true purple color within a day or two. We run our lights on a 16 to 17 hour daily schedule. Our full setup is in the microgreen lighting guide.

This is also when bottom watering begins. The roots are happy and reaching into the reservoir, so we stop misting the top and pour water into the bottom tray instead. Because it is the first time in light, we start small with about a half cup of Ocean Solution 2-0-3 water in the morning and another half cup at night. They do not need much yet.

Red cabbage microgreens just out of germination on a reusable silicone grow medium in an On The Grow Kratky tray kit

Step 5: Bottom Watering Through to Harvest

From here on, the routine is simple: bottom water once or twice a day, and increase the volume as the tray drinks more. We went from a half cup, up to about a cup, then a cup and a half, and finally around two cups a day as the plants got bigger and the medium started drying out faster. Watch the medium for dry spots, especially toward the back. If one side dries faster than the other, your surface is probably a little uneven, so tilt the tray to even out the watering. Keep an eye on the roots and keep them from drying out so they stay white instead of browning.

We use Ocean Solution 2-0-3 because cabbage grows fuller and heavier with a little feeding on coco coir or silicone. For watering volumes, schedules, and the full bottom-watering method, our complete watering guide goes deep. Note that on soil you generally do not need to add liquid fertilizer, since most quality soil mixes are already nutrient rich. If you want to compare feeding options, our best nutrients and fertilizers guide breaks them down.

Hand lifting a tray of red cabbage microgreens on a reusable grow medium with white roots showing underneath at On The Grow

Step 6: Knowing When to Harvest

Our grow was ready on day 13. A few signs told us it was time. First, in spots the microgreens were starting to separate and lean away from each other, which means they are getting tall and want to be cut. Second, we could see the first true leaves just beginning to poke through above the cotyledons. With cabbage that true-leaf stage is your cue. We did not water on harvest day.

Most Red Acre cabbage grows are ready in the 8 to 12 day range. We took ours a touch longer to get extra height for an easier cut, which is a personal preference and totally fine with this crop. Mammoth Red Rock often finishes a little quicker for us thanks to its shorter dark phase.

Close-up of red cabbage microgreens with deep purple stems and green cotyledons growing in a tray

Harvesting and Weighing

Use a sharp knife or sharp scissors so the blade glides through the stems instead of crushing them. A sharp tool makes the whole job faster and cleaner. We harvest into a bowl sitting on a scale so we can record our weights. If you are comparing harvest tools, we broke them all down in knife vs. scissors vs. electric trimmers.

One tip from the video: when you are growing on coco coir, do not cut right down at the base of the canopy. Cut a little higher so you do not pull medium up into your harvest. It saves you a lot of washing later.

From 21 grams of seed, our tray gave us 287 grams of fresh Red Acre cabbage microgreens. We were very happy with that. We also noticed a little late blooming in the canopy, a few shorter greens that germinated behind the rest, which is exactly why we would lower the seed density to about 17 grams on the next grow.

Handful of freshly harvested red cabbage microgreens with purple stems held over a growing tray

Check Your Roots and Store Your Harvest

After cutting, it is worth peeking at the underside of the tray to see the full root system. A healthy mat of interwoven white roots is a great sign. This is also a good moment to spot any trouble you could not see from above, like the browning that can come from overwatering or damping off. If you ever see mold during a grow, our mold prevention and identification guide walks through what to do.

[IMAGE: underside of the tray showing the dense white interwoven root system]

Bag your harvest and store it in the fridge. Even when you are sure you know what crop it is, write the variety and the harvest date on the bag. When you grow several brassicas that look alike, it is easy to mix them up, and a quick label saves the confusion. When the grow is finished, our guide on what to do with used grow medium covers cleanup, and our cleaning and sanitizing guide keeps your trays and reusable mediums ready for the next round.

Vibrant red cabbage microgreens with purple stems harvested into a glass bowl

Are Red Cabbage Microgreens Good for You?

Red cabbage microgreens are one of the more nutrient-dense microgreens you can grow at home. In the landmark 2012 study from the University of Maryland and the USDA, researchers tested 25 different microgreens and found that, in general, microgreens contained four to 40 times more of certain nutrients than their fully grown counterparts. Red cabbage microgreens stood out in that research for having the highest concentration of vitamin C of all the varieties tested, along with notable levels of vitamins K and E. You can read the University of Maryland summary of that work in their Mighty Microgreens article, and the original peer-reviewed paper is Xiao, Z. et al. (2012), published in the Journal of Agricultural and Food Chemistry.

Like other brassicas, red cabbage also contains plant compounds such as glucosinolates and antioxidants, and research has linked diets rich in these vegetables to a range of potential health benefits. We are growers, not nutritionists, so we always point readers to the research itself and to a qualified professional for personal guidance. What we can tell you from experience is that these greens taste mild and slightly sweet, and they are an easy way to add fresh color and crunch to almost any meal. For ideas, see our guide on easy ways to eat microgreens.

A Note on Growing Mediums

We grew this batch on coco coir, and Red Acre cabbage also grows well on soil or on our reusable silicone grow medium. The silicone is the one growing medium we make ourselves, and it is built to be used again and again across many grows. If you want the full medium-by-medium walkthrough for the standard tray size, see our 10x20 tray growing guide.

Frequently Asked Questions

How long do red cabbage microgreens take to grow?

Red Acre cabbage microgreens are usually ready in about 8 to 12 days from seed to harvest. In our video grow we took ours to day 13 on purpose to let the greens stretch a little taller for an easier harvest. Mammoth Red Rock often finishes a little sooner for us because we give it a shorter dark phase.

How much seed do I use for a 10x20 tray?

We recommend about 17 to 20 grams of Red Acre cabbage seed per 10x20 tray. We used 21 grams in the video and got a few late bloomers, so we would lower it slightly next time. For precise rates by tray size and variety, grab our free tray-specific seeding guide.

Do I need to fertilize cabbage microgreens?

Cabbage grows fine on plain water, but a light feeding of Ocean Solution 2-0-3 on coco coir or silicone tends to give a fuller tray and a heavier harvest. On soil you generally do not need liquid fertilizer, since most quality soil mixes are already nutrient rich.

Are red cabbage microgreens healthy?

Red cabbage microgreens are considered very nutrient dense. In the 2012 University of Maryland and USDA study, red cabbage microgreens had the highest vitamin C concentration of the 25 microgreens tested, along with notable vitamin K and E. As with any food, they are best enjoyed as part of a balanced diet. We are growers rather than medical professionals, so consult a qualified provider for personal dietary advice.

Why do you blackout under weight first, then switch to a dome?

The weighted phase encourages even germination and strong root contact with the medium. Once the seedlings are established, switching to a propped blackout dome lets them stretch taller before they hit the light, which makes for a cleaner, more uniform harvest.

Can I grow red cabbage microgreens on the reusable silicone grow medium?

Yes. Red Acre cabbage grows well on the reusable silicone grow medium, as well as on soil or coco coir. The silicone is built to be reused across many grows, so you can grow batch after batch on the same medium.

Is Mammoth Red Rock cabbage grown the same way?

Yes. Mammoth Red Rock cabbage is another favorite of ours, and it follows the same process as Red Acre cabbage from seeding through harvest. The main difference is timing. Mammoth Red Rock tends to be a bit more vigorous, so we usually run it about 3 to 4 days under weight and just 1 day of blackout, while Red Acre can be slightly slower and shorter and benefits from a little more time in the dark.

How do I store my harvest?

Bag your microgreens, label the bag with the variety and harvest date, and keep them in the fridge. Labeling matters more than you would think when you grow several look-alike brassicas.

Final Thoughts

This grow is the one that started it all for us, and the method still holds up years later. Red Acre cabbage is forgiving, beautiful, and a perfect crop to learn the full seed-to-harvest rhythm on. Once you have it down, the same five-phase process carries over to almost every brassica you will grow, including Mammoth Red Rock cabbage. If you want to go deeper, our beginner's guide PDF and our full Microgreen Masterclass cover every method and crop in detail, and you can find more of our grows over on the video library.

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Nutritional information shared throughout this blog is based on commonly available research, peer-reviewed studies, and public health sources. We are not nutritionists, dietitians, or medical professionals, and nothing in this post should be taken as medical or nutritional advice. Always consult a qualified healthcare provider for personal dietary guidance.

The results and opinions shared in this post are based on our own first-hand testing in our specific, controlled grow space. Any mention of a brand or product reflects our own experience, not a sponsored or definitive review. Your climate, water, seed, and setup are different from ours, so your results can vary. We always encourage you to run your own experiments and see what works best for you.

— On The Grow®, LLC

Happy growing!