How to Germinate Microgreens Part 4: The Hybrid Blackout Method

The Hybrid Blackout Method is the last in a four-part series on germinating microgreens.

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

The Hybrid Blackout Method is for microgreen varieties that have persistent seed husks, or it is to your advantage to grow taller quickly.

I also apply the hybrid blackout to vertically-challenged microgreens, as the dark, tall dome elongates the stems, making them easier to harvest.  

hybrid method with sunflowers

The Hybrid Blackout Method

As the name implies, the hybrid blackout method modifies not one but two different germinating blackout methods to improve results.

The three best examples are germinating sunflowers, pea shoots, and arugula. All for different reasons. 

I'll explain the reasons below, but first, let's talk about how the hybrid blackout method works.

How the Hybrid Blackout Method Works

The hybrid blackout method starts with the weighted blackout method.

With the weighted blackout method, the tray is placed under the lights once the seeds have germinated. However, in some circumstances, it might be beneficial for the germinated microgreens to remain in the dark.

But the close quarters under the weight will stunt or kill the microgreen growth.

So for a short time, we apply the domed blackout method, where the microgreens have a little more room for growth, and the humidity remains high.

The Hybrid Blackout Method Video - Quick Version

Why Not Use The Domed Blackout Method From The Start?

One would think it best to use the domed blackout method. After all, that is how we finish the blackout. So why not start with the dome method?

However, if you remember from the weighted blackout method article, the purpose of the weight is to promote strong root growth and sturdy stems. 

How to Start Microgreens: All my articles on germinating microgreens and the blackout period.

Taller microgreens and those with larger leaves need a robust root system and sturdy stem to hold themselves upright.

The domed blackout method will cause shallow root growth, and microgreen stems appear to have a smaller diameter than those grown under weights.

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Three Reasons to Use the Hybrid Blackout Method - With Examples

Here are the three reasons to use the hybrid blackout method.

Germinating Sunflowers

Sunflower microgreens, or as some people call them, sunflower shoots, have a persistent seed hull that often remains on the sunflower after germination. 

Sometimes it even stays on the microgreen after the cotyledons are several days old. Worst, some hulls are so persistent that they don't allow the cotyledons to spread out.

sunflower microgreen hulls stopping growth

Indeed, many of these hulls will eventually fall off. However, this sometimes only happens after the true leaf starts to form and increasingly forces the cotyledons apart.

I like sunflower microgreens' flavor before the true leaves form, as they are less bitter.

How the Hybrid Blackout Method Removes Sunflower Hulls

The hybrid method, starting with the weighted first stage, promotes a robust root system. This is because the lower stems become stronger as they lift the weight off themselves.

By adding the dome in the second stage, the dark dome increases the growth rate as the plants reach for the light that they instinctively know is upward.

The stems become more prolonged, and the upper portion of the stem is now more tender because of the freedom to grow quickly and without being held back by the weight.

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What also happens under the dome is that the humidity stays high. If you watched the quick video above - if you didn't scroll up and watch it now, it's short - you can see the moisture on the sunflower leaves.

The moisture does two things. One, it allows the more stubborn sunflower seeds to germinate. Not all sunflower seeds germinate at the same time. Some take longer, and the dome's humidity triggers more germination.

Second, the persistent sunflower hulls remain wet and soften up, making it easier for the cotyledons to shed the hulls naturally or with a light brushing with your hand.

hulls shedding off germinating sunflowers

Here are the benefits of the the hybrid blackout method.

  • It has produced sunflower shoots with a strong root system.
  • The lower stems are sturdy.
  • The upper stems are more tender.
  • More sunflower seeds will germinate, and seed hulls are easier to remove by themselves or with a light brushing with your hand.

However, as successful as the hybrid method is with removing persistent microgreen hulls, I do not use the method with microgreens such as beets and Swiss chard.

These tender stemmed microgreens will not hold up to the extra humidity and wetness.

How the Hybrid Blackout Method Makes Pea Shoots Taller Quicker

Pea shoots, like sunflower shoots, need a robust root system to support the tall leafy shoots, and let's face it, the taller a pea shoot is, the more there is to eat.

As discussed in the section about germinating sunflowers, the first phase of the hybrid blackout method forces microgreens to grow a robust root system and sturdy lower stems.

When microgreens receive light, the leaves increase in size to absorb light and start photosynthesis. Unfortunately, this process slows the vertical growth rate of plants.

The purpose of the second phase of the hybrid method (doming) is to delay leaf growth and increase stem length as the plants search for light.

tender pea shoots

The elongated stems are more tender and less woody than would be otherwise.

The tender pea shoots shown above have been removed from the hybrid blackout and have spent their first day under the light.

Once the pea shoots reach the top of the dome and are released to the light, more leaf nodes will form, producing better pea shoots and more volume and mass.

Like the tray of pea shoots shown below.

full tray of pea shoots

I always use the hybrid blackout method to grow pea shoots.

The Hybrid Method Can Be Used On Vertically Challenged Microgreens

Some microgreens grow short.

Not that being short is terrible because that is how they grow naturally.

However, the downfall comes when you try to harvest short microgreens.

It is harder to cleanly harvest microgreens like arugula and sorrel because the leaves are so close to the soil (or grow mat) surface.

Like the red-veined sorrel microgreens shown below.

red veined sorrel microgreens

This is especially true if the grow media is below the edge of the tray.

The hybrid blackout method can help make harvesting these shorter microgreens easier.

It is the same process as with peas. The second phase of the hybrid method will increase the length of the stems.

Like the tray of arugula shown below grown by the hybrid method. Even slightly longer stems make harvesting easier.

tray of arugula microgreens

Same process same result, but for different purposes.

The hybrid method will not add much extra mass or volume to microgreens like arugula or sorrel.

But, it will cause the stem to grow a half-inch to an inch taller, making it much easier to harvest these tasty microgreens.

Summary of the Hybrid Blackout Method

The hybrid blackout method is a combination of two previously discussed methods. The weighted blackout method and the domed blackout method.

In the first phase of the hybrid method, you follow the procedure of the weighted method to increase seed germination and develop a robust root system and sturdy lower microgreen stems.

In the second phase of the hybrid method, instead of placing the microgreen tray under lights, you place a dome over the top of the germinated microgreens.

The hybrid blackout method is finished when the microgreens reach the top of the dome.

The purpose is to increase the stem length and, if needed, soften up the seed hull so they shed off the microgreens more easily.

Even though the hybrid method softens seed hulls, it should not be used on water-sensitive microgreens like beets and Swiss chard. The extra humidity and moisture will cause problems with these types of microgreens.

I successfully applied the hybrid blackout method to sunflowers, peas, arugula, and sorrels.

if you haven't read the first 3 articles in the how to germinate microgreen series you can access them by clicking the links below.

How to Start Microgreens: All my articles on germinating microgreens and the blackout period.

If you like these articles and want to learn more tips and tricks as well as receive how-to-grow microgreen articles be sure to sign up to get an email when a new article is published. 

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Author of this Article is Todd

Todd is the founder of Home Microgreens & the Home Microgreens store. He also writes for several other websites, including

His microgreens have appeared in Better Homes & Garden magazine and other websites.
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. He will be in the garden, trout stream, or on a mountain trail with his Springer Spaniel Caden when not at the computer.

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