How to Germinate Microgreens: Part 2, The Buried Blackout Method

This article on the Buried Blackout Method is the second in a four-part article and video series on how to germinate microgreens.

There are links to the other articles in the series below.

The Buried Blackout Method is similar to the weighted blackout method in that you place a weight on the tray once you finish sowing the seeds.

The difference is how we plant the seeds.

In the buried blackout method, less soil is initially placed in the tray. Then, the seeds are sown on the lower surface before being covered with additional soil. Hence the name buried blackout method.

The Buried Blackout Method Explained

You might be asking why we would want to bury seeds with soil. Especially since in Part 1 of this series, I said that the weighted blackout method could germinate all microgreens.

There are two reasons I use this method.

Reason One

The first reason is that some seeds tend to dry out during germination.

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Because large seeds, like peas, create a gap between the soil and cover when using the weighted blackout method and allow moisture to escape. 

In larger trays, more weight can be added to reduce the gap, but smaller trays aren’t as sturdy, and heavier weights can’t be used.

Or, whole cilantro seeds that take a long time to germinate can dry out, or the extended time allows mold to develop.

Burying seeds keeps moisture around larger seeds. Also, the soil naturally keeps mold from growing on those that take several days to germinate.

Reason Two (the most common reason)

Some microgreen seeds contain a hard husk that remains on many microgreen plants as they grow.

These hard husks are challenging to take off the plants and are definitely not edible.

Beet and Swiss chard, cilantro (whole seed – the split seed doesn’t seem as bad), buckwheat, sunflower, and probably a few others are the common seeds with hard husks.

I use the buried blackout method mostly with beets, Swiss chard, and sometimes with cilantro (coriander). I use another sunflower germination method. I will discuss germinating sunflowers in this series’s fourth part.

The How to Germinate Microgreens Series

How Does The Buried Method Remove the Husk?

I realize we haven’t discussed the methods behind the buried method. Still, it is probably self-evident that we will bury the seeds.

However, burying the seeds isn’t enough.

We still need to add weight on top of the tray. As the seed germinates, the friction of the soil and the amount of force required by the plant to overcome the weight will pull the spent seed husk off of the seedling.

I have read that pre-soaking beet and Swiss chard seeds remove the husks, but in three attempts of pre-soaking beet seeds, it didn’t seem to make a difference. 

How to Germinate Microgreens Using the Buried Blackout Method

The video below shows a snapshot of the tray preparation method and the results when the microgreens germinate.

Videos in the Home Microgreens Fundamental Microgreen Growing Course show the process at a slower speed with a descriptive narrative. 

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Preparing the Trays for the Buried Blackout Method

The first step is to find a tray, sheet pan, or something larger than the microgreen tray you will use. 

The tray below is a Doughmate Artisan Dough Tray.

Soil is not messy if a couple precautions are taken. Notice I made the video in my living room on my coffee table. I have no worries about a mess. 

Step 1: Partially Fill the Planting Tray

Fill your planting tray (the one with holes) with soil and slightly compact the soil to about 1/8- to 1/4 inches below the top rim.

It is easier to spread the seeds evenly if the surface is semi-smooth.

Step 2: Wet the Soil Surface

Take a spray bottle and wet the soil surface. As with all my germinating methods, wetting the whole soil profile is unnecessary. The seeds do not need water at the bottom of the tray.

If you are planting seeds in a larger tray, I use a handheld sprayer like this Vivosun Garden Sprayer or a hose connected to a facet.

Step 3: Spread the Seeds Across the Soil Surface

Next, spread the seeds as evenly as possible across the soil surface. For larger seeds, I like to use the 250-mL measuring cup.

I use the same measuring cup to seed larger 1010 or 1020 trays. 

You can clearly see that the soil level is down by the lower lip on the Home Microgreens Tray.

Step 4: Mist the Seeds

Once the seeds are spread on the soil surface, mist them one or two times with water.

Step 5: Bury the Seeds and Wet the Surface

Now it’s time to bury the seeds.

Place enough soil over the seeds to fill the tray. Again, compact the soil with your hand. Good soil will not compact tightly but spring back up, nestling the seeds in a protective coating but not so much to discourage oxygen exchange.

I clean off the tray’s rim so the soil doesn’t make a mess and for a lid or tray separator to rest on top of the rim.

Once the surface is smooth, wet the soil to help it stay in place and give the plants a little more resistance to germinate.

Step 6: Place the Tray in the Weighted Blackout

From here on out, the process is precisely like the weighted blackout method.

At this point, I put the planting tray inside the watering tray so no soil falls from the bottom – again, using soil does not have to be messy.

Place a tray lid (upside down) or a tray separator over the tray and put the whole set up in a location that is out of the way.

Instead of the lids that come with the Home Microgreens Trays, I’ve been using coroplast tray separators.

Coroplast is corrugated plastic like they use for all of those annoying political signs placed every 10 feet at road intersections.

I buy my sheets from Michaels Crafts and cut them up. But, they are a pain, so if you don’t want to go through that, I started to offer them pre-cut in the Home Microgreens Store.

Step 7: Add Weight and Cover Up the Tray

Once the tray has a location, I place the weight on top of the lid or tray separator.

I discussed the weight I use on each tray type in Part 1 of this How to Germinate Microgreens Series. You can get that information from that article. 

At this point, I place an inexpensive tea towel over the works, turn the lights off, and let the seeds germinate for a few days.

When to Remove the Tray From the Buried Blackout?

From this point on, the process is like the Weighted Blackout Method.

Place the young microgreens under the lights when they have germinated and grown to the point where they look like they are trying to escape from weight by growing sideways. 

In the video near the beginning of the article, there are several frames of the growth stage of Bull’s Blood Beets. The first is as they start to grow out of the soil.

Be aware that plants might take a day or two longer to appear as they have to grow up through the soil. 

The second image is still too early to remove the weight, and they should go back into the blackout.

The young beet microgreens in the third image are ready to go under the lights.

Lastly, the fourth image is the same tray of Bull’s Blood Beets after a day under the lights. 

Growing Beets and Swiss Chard

Here are some articles showing the buried blackout method in action.

The Secret to Removing for Removing the Seed Husks from Beets
How to Grow Swiss Chard Microgreens Without the Nasty Seed Husks
How to Grow Vibrant Magenta Sunset Swiss Chard Microgreens

The Buried Blackout Method is Very Useful

The weighted blackout method is the most common way to germinate microgreens. All microgreens can be started using that method.

But that doesn’t mean there aren’t better ways to germinate some microgreen varieties.

The Buried Blackout Method has proven to be an effective way to remove those persistent hard husks on beet and Swiss chard microgreens.

I often also use it when I plant whole cilantro seeds. However, I find that my germination of cilantro is often better when I use the buried blackout method.

I hope you found this article helpful.

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