Microgreen Growing Mediums: What We Found to be the Best

We continue the series on microgreen growing mediums by changing the microgreen trays and adding one new microgreen growing medium.

Instead of trays 1-1/2 inches tall, we tried shallower-sided trays. In the last article, the taller sides of the trays appear to restrict the growth of the microgreens.

The microgreen growing mediums comprised our Home Microgreens Potting Mix, Terrafibre Hemp Matting, and bamboo grow matting. In addition, we added a thick coco-coir grow mat.

You can see the microgreen growing medium in the photo below. The other articles and videos in the series are also included below.

Choosing the Microgreen Growing Mediums

 The microgreen growing media in the photo are from top to bottom are:

Home Microgreens Potting Mix

This is our favorite microgreen growing medium. We believe in soil for several reasons.

1. Nothing has outperformed or grown microgreens better than Home Microgreens Potting Mix in any of our trials.
2. Seeds are meant to grow in soil.
3. We utilize the soil for other growing purposes and in the garden after growing microgreens.
4. Coconut coir fiber is a waste product, so using products like this makes a lot of sense.

The main reason is that nothing we have tried grows microgreens as quickly as the potting mix.

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We have tried many different media, and this is the best so far.

Many of these trials are published on this website. Unfortunately, many other media were complete failures.

Home Microgreens Potting Mix contains coconut coir, peat moss, and many natural amendments and minerals.

Bamboo Grow Mats

Bamboo is a very renewable material. The plant will regrow quickly, so there is no re-planting, no fuel use, or soil disturbance. However, it doesn’t grow everywhere, so it’s debatable if it is sustainable.

We like this microgreen growing medium because it is:

1. Very clean, with no dust or fibers when cut.
2. Retains water well.
3. The material is light, thus reducing shipping costs.

However, bamboo fiber is tightly woven and not very thick, which might make it difficult for roots to penetrate.

TerraFibre Hemp Matting

We like TerraFibre for quite a few reasons.

1. It is easy to procure in mass
2. Hemp fiber mats are lightweight and easily stored.
3. TerraFibre is a popular product, and many people know how to use it.
4. The hemp grow mat is thick and not woven tightly, allowing roots to penetrate the material more easily.

Hemp, and items made from hemp, are often labeled sustainable. Yes, it can be grown in more locations than bamboo. However, it needs to be re-planted and often in tilled soil.

But it is a better material than peat moss, which is probably being mined quicker than new peat bogs are forming.

We are not in love with hemp grow mats because of the number of fibers that fall off the product when placing it in trays or trimming it to fit into trays. 

It is much messier than soil.

Coco Coir Grow Mats

We were shipped a case of coco coir grow mats to try quite a while ago and have never tried them. 

The main reason is the amount we need to purchase to stock the grow mats. 

But, tired of seeing them lay around, we decided to give the go this time.

We like coco coir grow mats because:

1. They are thick and loosely woven – airy, making growing roots easy.
2. Coco coir holds a lot of water. However, unlike the other mats or finely ground coir, these mats may need soaking.
3. They are a stiff mat, making them easy to move around during growing and at harvest.
4. Fibers are less of an issue than hemp, only shedding when cut to shape.

The fibers in coconut coir grow mats are much longer than what is contained in potting mixes. So adding amendments to them pre-watering is not possible. So unlike the HM potting mix, liquid fertilizer is necessary to grow great microgreens.

Microgreen Growing Mediums Comparison Video

In the video below, we show how each microgreen grow media is prepared and planted and the growth stages of the microgreens throughout the test. 

The results and recommendations are also presented.

The Low-down on the Microgreen Grow Medium Test

As shown in the video, we grew Mighty Microgreen Mix on trays with around 38 square inches of surface area.

The Home Microgreens Potting Mix is placed in an HM planting & watering tray.

The fiber grow mats were placed on shallow trays about the same size.

Mighty Micro Microgreen Mix contains Broccoli, Red Russian Kale, Red Acre Cabbage, and Komatsuna seeds. It is very popular in the Home Microgreen Store and with our retail & wholesale microgreen customers.

By the way, if you like the large green tray, you can purchase them here.

Wetting the Microgreen Grow Media

The grow media are pre-wetted with a spray bottle. The potting mix needs a few more passes to get the moisture down about 1/4 to 3/8 inches.

The bamboo and hemp fiber mats wet quickly and easily.

We had difficulty determining if the coco coir mat was wet enough. Presoaking the mats for an hour or more might be better to pre-wet coco coir grow mats.

Seeding the Microgreen Grow Mediums

Each tray received three grams of Might Micro Mix spread as evenly as possible. 

The potting mix, leveled and tamped before wetting, was the easiest to use. 

The bamboo and hemp mats are quite uneven (I didn’t want to compact the fibers more than they are), and seeds roll into low spots on the grow mats.

The coco coir grow mat took the seeds; some bounced off, and most disappeared into the weaves of the fibers making it more difficult to tell where to seed.

After the seeds are spread, they are misted to wet and settled into the grow media.

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Blackout Period

Each tray is placed into a blackout period by covering the tray with a plastic lid, placing 2-1/2 pounds of weight on the lid, and covering the tray with a towel to exclude light.

The trays are kept in the blackout period for three days, about 72 hours.

Removing Microgreen trays From the Blackout Period

On day three, the towel, weight, and lids are removed from the trays and put beneath a light bank.

The lights are two Barrina 24-watt grow lights. We are trial-testing these lights, which are working out great so far!

The lights to the naked eye are white or natural, but the camera picks up more on the red LED light. 

From left to right, the microgreen growing mediums are coco coir grow mat, TerraFibre grow mat, bamboo grow mat, and Home Microgreens Potting Mix.

The grow mat trays are elevated to bring them as close to the lights are the potting mix tray.

The trays are also watered for the first time. We use Ocean Solution, an organic liquid fertilizer, at a rate of 1 ounce per gallon of water. Even though the potting mix doesn’t need to be fertilized, we did since the water is right there. 

The video shows close-ups of each tray. 

First Day Under the Lights

The growth on the potting mix and coconut coir grow mat are impressive after one day. 

Again, the video shows close-up photos of each tray. But without a doubt, the soil and coco coir grow mat is doing better.

You can see where we missed adding seed to the front right corner of the coco coir grow mat. If we had presoaked the coco coir grow mat, we would have had better results along the edges of the mat.

Cut to the Chase – Which Microgreen Grow Mediums Are the Best?

Here is a photo of the result. The video goes into more detail on the results.

The microgreen growing mediums are from left to right; coconut coir grow mat, Terrafibre hemp grow mat, bamboo grow mat, and Home Microgreens Potting Mix. 

Without a doubt, the Home Microgreens Potting Mix did the best, also, with less work and worry. 

The thick coconut coir mat (left photo) did well too. The leaves aren’t quite as large, and neither is the total canopy size. 

The TerraFibre hemp grow mat didn’t do as well as in the previous test. The bamboo did the worst of the bunch, although the stems’ color seems brighter than the others. 

Easy of Care with Microgreen Growing Mediums

Preparing the grow media for planting

Regarding preparing the growing mediums, the bamboo grow mat is the easiest to work with. It is thin, folds and unfolds nicely, wets well, and can be stretched to fit the tray.

To me, the soil is next. Yes, we recommend keeping soil in a container, so there is that, but as long as you have a container under the tray when filling it, there is no mess.

Also, the surface can be made very smooth, making it much easier to seed.

The TerraFibre is so messy because fibers are always falling off it. Even with a container beneath it, the fibers fly around and stick to clothes and everything else when cutting and handing.

It wets well, but the surface is hard to make smooth. 

The coco coir fiber mat is challenging to store because it is stiff and oversized. You can cut it with a good pair of scissors, but it isn’t like cutting through butter. Maybe like cutting frozen butter.

Coir matting is also challenging to wet on the fly. It is hard to know when it is wet enough. Soaking that beforehand is the way to go. But I rarely plan when I’m going to plant microgreens. I do it when I have time. One more thing to think about and plan out.

Care of Microgreens on the Growing Mediums

We give this one to the potting mix. It is easy to tell when it needs water and takes up water quickly from the bottom. Because of the thickness and mass of the growing medium, it doesn’t need to be watered as often.

The other grow media mats are about the same. However, it is difficult to tell when it needs water, and without the reserve of media mass, it can dry out quickly.

Easier to make a watering mistake with the grow mats. So if you are busy and forget about your microgreens, soil is the best microgreen growing medium for you.

Growth of Microgreens 

The potting mix grows microgreens larger and quicker than any other growing medium.

Again, look at the photos in this test and the microgreen growing medium tests we have done.

Also, there is no need to buy fertilizer. None is needed for tremendous growth. Not so with any of the grow mats.

Recommendations for Microgreen Growing Mediums

We will continue to grow microgreens in a potting mix. No more tests between soil and grow mats are necessary. 

Right now, the coconut coir grow mats seem to do a great job. 

In the video, I was hedging which microgreen grow mats to stock in the Home Microgreen Store.

But we’ve decided to continue to carry the TerraFibre hemp grow mats.

We have also found a supplier for coconut fiber grow mats and will carry those as well.

Ultimately, what microgreen growing mediums you use doesn’t matter to us. We will try to provide as much information as possible for each type. 

We only want you to grow microgreens and other food sources at home. As food prices increase, the quality and comfort of where food is grown go down. It makes sense to start exploring more local avenues for food procurement. 

Growing your own is as local and as fresh as you can get!

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