How to Grow Wasabi Microgreens: Spicy Not Hot and Easy to Grow!

If you like spicy flavors, then you need to try wasabi microgreens!

Wasabi microgreens are not hot; instead, they are spicy.

There’s a difference, at least to me. Hot is like eating a hot sauce where the flavor and heat stay with you. It continues to burn after you’ve eaten the food.

On the other hand, spicy has a similar heat-like flavor, but the heat or spiciness goes away once you have eaten the food. Only the taste remains on your palette.

The latter is the flavor that wasabi microgreens have. You get that initial spice and heat, then the only taste with no need to run to the refrigerator to get a glass of milk.

Below we will show you how to grow this flavorful and fantastic microgreen.

wasabi microgreens

Wasabi Paste is Not Made From Wasabi Microgreens

To begin with, we want to be clear that the wasabi paste used frequently in Japanese and other Asian food is not derived from the same seed or microgreens.

Wasabi paste is made from the rhizomes of Japanese horseradish or Wasabia japonica.

Wasabi microgreens are grown from a variety of mustard named Brassica juncea.

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FREE Home Microgreens Grow course that teaches you the basics of growing microgreens in your home! There are 12 video lessons (over 120 minutes), downloads, and more written information and tips!

However, both are related as Japanese horseradish and wasabi mustard are in the family Brassicaceae.

But the flavors are similar. 

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How to Grow Wasabi Microgreens

Growing wasabi mustard microgreens is very easy. 

We grow them in two ways.

Both work well, and our chosen method usually depends on the space we have available on the microgreen shelves.

Adding Soil to the Microgreen Tray

We would instead use soil to grow microgreens. We stated the many reasons why soil is better in several posts.

Fill the tray to the top edge with loose potting mix (we, of course, use Home Microgreens Potting Mix) and lightly tamp the soil with the palm of your hand.

Level the Potting Mix

Next, use the lid upside down or some other firm object that will fit inside the tray and pack the soil to be level and smooth.

Firming the soil will put the level to about ⅛- to ¼-inch below the top edge of the tray.

The soil surface should be smooth because the wasabi mustard seeds are tiny and rolly. An irregular surface will collect seeds instead of spacing them out evenly.

leveling the soil

Wetting the Potting Mix 

Use a mist bottle to wet the soil surface.

We do not recommend saturating the soil to the bottom of the tray. The extra moisture can only cause problems later on.

The seeds only need the upper third of the soil column to be moist.

wetting beet microgreen seeds

Now the soil is ready to accept seeds.

How Many Wasabi Mustard Seeds per Tray?

The Home Microgreen tray is about 7.5- by 5 inches, and we use 1.8 grams of wasabi mustard seeds. A 1010 tray uses between 4.7- and 5 grams. 

We do not like to pack seeds completely onto the tray. We give microgreens room to spread their leaves and collect energy from the lights. 

wasabi seed

We have you covered if you don’t have a Home Microgreens tray. 

Measure the dimensions of your tray and use the Home Microgreens Seed calculator to figure out how many seeds you need.

Spreading the Wasabi Seeds

Next, spread the seeds evenly on the soil surface.

We use a shaker bottle as the seeds come out slower. Circle the outside of the tray, and then fill in the middle.

Try not to use all of the seeds on the first go around.

Save some to fill in areas where you may have missed.

Use your fingers if you find an area that is too dense. The seeds are round and will move easily on the smooth soil surface.

Spacing them will give you better results.

Don’t worry if they look sparse. The plants will fill in the gaps.

Too many seeds lead to problems like fungus and tiny undersized microgreens. You will see how full the trays become when fully grown later in the article.

wasabi microgreens seeds

Two Blackout Methods to Grow Wasabi Microgreens

There are two primary blackout methods.

We call these the Weighted Blackout Method and the Domed Blackout Method.

The names are pretty much self-explanatory.

Both methods darken the seeds by excluding most, if not all, light.

Below we will briefly explain the methods, and for more information, check out our online course.

The Weighted Blackout Method for Mustard

The weighted method uses a lid or a cover to apply pressure to the seeds and force a better seed-to-soil contact.

You can use any weight, but it’s best to find a weight large enough to apply even pressure across the cover.

The amount of weight depends on the size of the tray and the type of microgreen. 

Small Trays & Thin Stemmed Microgreens Such as Mustards

Use less weight as the tray walls might distort under the weight (treat trays well, and they will last many years).

Thin stemmed microgreens such as mustards don’t have the power to lift a heavy weight. Too much weight might affect their growth, so it’s best to err on the side of caution.

We use 2.5 pound weights for small trays.

weighted blackout method
covering up microgreens for blackout

The last step is to cover up the trays. If the lid or cover is opaque or doesn’t completely cover the tray, use a tea towel or two to block the light.

For our heavy-duty shallow 1020 microgreen trays, we will use two or three 2.5-pound weights.

If you have more than one tray of microgreens, stack up the trays and use less weight on the very top. 

microgreen in a blackout period

The Domed Blackout Method for Mustard

The domed method is easier to implement than the weighted method.

All that is needed is a tray of similar size (larger is good, too as long as there’s an inch or more of clearance above the planting tray).

Place the empty tray on top of the planting tray forming a dome. 

The Home Microgreens Planting and Watering trays are perfect for the domed method. Use the opaque lid under the planting tray to capture any potting mix that might fall out the holes.

At this point, the watering tray is placed over the planting tray forming a dome.

That is it. 

shallow tray under the blackout dome

Advantages of One Method Over the Other

Both methods have their merit.

The weighted method works great for vigorous-growing microgreens. Promoting deeper rooting and stronger stems. Microgreens that take several days to germinate also benefit from the weighted method, as moisture is better retained.

The domed method is excellent for thinner stemmed microgreens and those that tend to stay short such as arugula.

Ending The Blackout

The most common question we receive concerning the blackout is when to end it and place the microgreens under lights.

We wish there were a set time, but there are so many variables, such as temperature, moisture, humidity, and even seed genetics; we can provide some keys to help you know when the time is right.

Removing Wasabi Microgreens From the Blackout

If you use the weighted method, you want to wait until the plants have started to push the lid off the tray. Or when the seedlings have grown stems and are looking for a way out from under the lid.

With the weighted method, removing the weight sooner is better than leaving it on too long. But the seedlings can grow quite a bit under the weight, as the photo shows below.

With the domed method, it’s easier to tell when to remove the dome. Remove the dome once the seedlings have reached the top.

Below is a photo of wasabi mustard seedlings after 3-days growing using both methods. The weighted method is on the left, and those grown under a dome on the right.

wasabi mustard out of blackout

The wasabi seedlings are yellow but will green up once they receive light. The bend-over stems on the weighted tray will straighten out.

The white fuzzies near the soil on the domed tray are root hairs and not mold. They will disappear in a day.

As you can see, the weight forced the plants to set roots and push the lid and weight off themselves.

Under the dome, conditions are perfect for roots to grow and get moisture from the damp air under the dome and have no reason to grow downward.

Place the Wasabi Mustard Seedlings Under Light & Water

When your wasabi microgreens have reached the stage above, it’s time to place them under lights and give them water.

The color temperature of your lights should be greater than 5,000K. We recommend using these lights for 2-foot-long shelves and 4-foot-long shelves. 

We recommend bottom watering all microgreens. It’s better for the plants and better for you.

Remember that we don’t recommend soaking the whole soil profile, so it’s time to add water.

Before you add the water, lift the tray and remember this weight. You will use this weight as a key for later watering.

Pour about 1/4-inch of water into the watering tray and slowly place the planting tray into it. The potting mix will draw up the water wetting the soil. 

After one day, you won’t recognize the wasabi mustard microgreens. The yellow plants will be green, and upright, and the root hairs will start to disappear.

wasabi mustard microgreens

Caring for Wasabi Microgreens As They Grow

Caring for your microgreens is easy.

All you need to do is keep them under the lights and water when necessary.

In the previous section, we asked you to remember the weight of the microgreen tray when you removed it from the blackout period.

When the tray gets to that weight again, add more water. 

Another benefit that the Home Microgreens trays have is that it’s hard to overwater. The water will overflow if you add too much. So start with a 1/4-inch of water and let it soak into the potting mix. 

Lift the tray again and judge if you should add more water.

Common Mistakes with Wasabi Microgreens

Wasabi Microgreens are easy to grow.

The most common mistake is to overwater the microgreens.

Another mistake are leaving the weights on too long, although they usually recover from this.

With the domed method, you can remove the dome too soon, and the shallow-rooted seeds will dry out. 

Be sure to leave the dome on until the greens reach the top of the dome.

Harvesting Your Wasabi Microgreens

Under the right conditions, you can harvest wasabi microgreens in as few as 8-days. More commonly, it takes 10 to 12 days before they are ready for harvest. 

In the first stages, you’ll harvest the microgreens in the cotyledon stage.

Wasabi microgreens can be grown until they sprout their first true leaves. This takes about 25 days. Some people prefer the taste of mustard microgreens at this stage. 

Like the wasabi microgreens below grown in the Home Microgreens Tray.

We wait until they are 3- to 4-inches high and use scissors or a sharp knife to harvest what we need for that meal.

wasabi microgreens ready for harvest
tray of wasabi microgreens

 Below we’re harvesting peas, but the process is the same, except wasabi microgreens are cut closer to the soil.

harvesting pea shoots

In the photo below, the wasabi microgreens show their first true leaves.

wasabi microgreens

The advantage of growing microgreens at home is that you can harvest as much as you need and continue to let the rest grow until you are ready for more. Food is more nutritious and flavorful when fresh.

You can’t get fresher than growing microgreens at home.

After Harvesting Wasabi Microgreens

If you need to harvest more than you can use, place them in a dry zip lock bag and poke a few holes in it. Squeeze out the air and put it in the crisper section of the refrigerator. 

Do not wash microgreens before storing them. Wait until you use them, then, by all means, rinse them. Washing before storage will greatly reduce their shelf-life. 

Wasabi microgreens are cut below the first leaves so they will not grow back. A few of the remaining seeds might sprout but not enough so to make it worthwhile.

For several reasons, we do not recommend reusing the soil. You can read more about reusing soil by clicking this link

How to Use Wasabi Microgreens in the Kitchen

Like the actual wasabi root, wasabi microgreens are fantastic to use with seafood. 

Whether this is with sushi, in California rolls, wraps, fish tacos, or an edible garnish to salmon or whitefish dishes. 

We use wasabi microgreens in tacos or burritos and on nachos, 

In non-meat dishes, wasabi microgreens are great in spring rolls, lentils, or mixed in hummus.

Where to Buy Wasabi Microgreen Seeds

Home Microgreens carries wasabi microgreen seeds in the perfect size packets for the Home Microgreens tray and 1010 trays. We also have one-ounce, quarter-pound, and pound bags when this microgreen is in stock.

Do You Have a Pinterest Microgreen Board?

If not, why not start one! Use this pin as the first or add to your existing boards.

wasabi microgreen article


  • Todd

    Todd is the founder of Home Microgreens & the Home Microgreens store. He also writes for several other websites, including MyViewFromTheWoods.com. Todd worked at a large farm market, garden & nursery center for 20 years. Somehow he snuck off to become a geologist and professor before coming back to his senses to write & lecture about microgreens and gardening. When not at the computer, he can be found in the garden, trout stream, or mountain trail with his new Springer Spaniel Caden.

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