An Organic Microgreens Fertilizer: Do Microgreens Need Fertilizer?

I ran a microgreens fertilizer test trial on a product a customer mentioned in an email. He mentioned how well his microgreens are growing when using this fertilizer. 

It has been a while since I ran any tests, and it was a great opportunity to get back to what built this website.

Besides showing the fertilizer’s results, I will provide my best guess on improving growing microgreens in pure coconut coir instead of a potting mix.

do you need to use a microgreens fertilizer

Do Microgreens Need Fertilizer?

That is the purpose of this article. The trial will show what type of microgreens need fertilizer the most, also, how microgreens respond to fertilizer depending on the media used to grow them.

Before I mention the fertilizer, I want to discuss how I set up the trial.

Two sets of four trays were grown. The seeds are Purple Vienna Kohlrabi as the faster-growing microgreen—and Genovese Basil as the slower-growing microgreen variety.

The four trays in each set are filled with pure coconut coir and Home Microgreens Potting Mix. One tray of each soil type will be watered with tap water and the other with fertilizer.

Why Home Microgreens Potting Mix and Pure Coconut Coir

I choose HM potting mix because, so far, in all of the tests I’ve done, the HM Potting mix has outperformed all other potting mixes.

home microgreens sells seeds

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When I say pure coconut coir, I mean coir that has been hydrated from a block and separated, similar to a potting mix.

Pure coconut coir is what many seed companies and other microgreen websites recommend using because of its availability and cost.

Some seed companies call this “Minute Soil,” just like those Jiffy pellets you can buy at any garden center or home improvement store.

I have many similar tests on different potting mixes and grow mats like Terra Fibre, bamboo, and fertilizers. You can see links to these tests on my Article Directory Page.

What Will This Test Show?

Ultimately, we will know if fertilizer is needed to grow microgreens for fast-growing microgreens. Those that take less than 14 days to grow.

Also, if longer growing microgreens, those that take over 14 days to grow, benefit more from the fertilizer.

Besides the effects of the fertilizer, the test will compare how each type of microgreen grows in my potting mix and the most common soil media used to grow microgreens. Furthermore, will adding a liquid fertilizer improve growth in the HM potting mix since it contains natural soil amendments?

In the video below, you can see the results of the test and my thoughts on the results of the test.

Below the video, I will include screenshots of the microgreens from the video and a summary of the results.

The fertilizer tested in this trial is Hero Organic Plant Food produced by Nature’s Lawn and Garden. More information on the fertilizer is included in the video and further down in the article.

I was sent the fertilizer to use, but Nature’s Lawn and Garden, and the person that sent me the fertilizer has no idea I did this trial, created this article, or produced a video. I have no affiliations with either. 

The video will have much more information and details than the written summary.

Video: Microgreen Fertilizer Trial Using Hero Organic Plant Food

Growing Purple Vienna Kohlrabi With and Without Hero Fertilier

Purple Vienna Kohlrabi is a quick-growing microgreen. You can go from seed to harvesting this microgreen in as little as ten days. Because it has a beautiful stem color and grows quickly and uniformly, I think it’s the perfect microgreen for this test.

Here is the seed used in the test.

Review of the Testing Procedure

Two Home Microgreens trays are filled with Home Microgreens Potting Mix and two with coconut coir.

The surface of the soil is tamped and pre-wetted. Each tray is planted with exactly 3 grams of kohlrabi seed, wetted, and placed in a weighted blackout.

After Three Days

Three days after planting, the kohlrabi microgreens are ready to come out of the blackout. At this point, I will also give them water for the first time. I water them with ½-cup of water from the bottom. I never water microgreens over the top of the plants.

One tray of each soil type will be watered with tap water—the other tray with the recommended application of Hero Organic Plant Food.

kohlrabi microgreens fertilizer test
The two trays on the left are Home Microgreens Potting Mix, and the right 2 are pure coconut coir.

Mixing the Hero Organic Plant Food

The recommended application is 1-2 ounces of Hero concentrate to a gallon of water. I followed these instructions adding 25 to 30 milliliters of fertilizer to a half gallon of water.

I shook the concentrate well before measuring out the dosage.

More notes on the fertilizer are below the results.

Hero Organic Plant Food

After Five Days

The trays are labeled as follows, and I assume they are self-explanatory.

  • HM Mix No Fert
  • Coir No Fert
  • HM Mix Hero
  • Coir Hero
kohlrabi microgreens after five days
Left to right: HM Mix no fertilizer, Coir no fertilizer, HM Mix with Hero, and Coir with Hero.

The kohlrabi in the HM Potting Mix is a bit taller than those grown in pure coir. The fertilizer doesn’t appear to be making any difference so far.

Purple Vienna Kohlrabi After Day 10

The two trays grown in the Home Microgreens Potting Mix are ready to be harvested.

The microgreens are taller and have larger leaves than those grown in pure coconut coir.

Kohlrabi microgreens after day 10 using fertilizer

All four trays of the microgreens look great, but as mentioned, those grown in the Home Microgreens Potting Mix are ahead of those grown in coir.

Adding Hero Organic Plant Food does not make a difference with these quick-growing microgreens, either in the Home Microgreens Potting mix that already contains nutrients or the pure coir that contains nothing. 

As we will see later (if you haven’t already watched the video), the Hero Organic Plant Food does help microgreens grow, so why didn’t it affect the kohlrabi?

Also, if the added nutrients in the Hero didn’t make the microgreens in the coir grow faster, why did the nutrients in the Home Microgreens Potting Mix help grow the microgreens quicker?

I’ll discuss my thoughts on this later. 

For Reference – Kohlrabi Microgreens After Day 12

After two more days, the growth rate is about the same. The Home Microgreens Potting Mix grows Kolhrabi about two days quicker than pure coir or “minute soil” would, as the microgreens in the coir are about the same size as the HM soil two days ago.

using a microgreens fertilizer on kohlrabi microgreens

Spoiler Alert – Hero Organic Plant Food Does Help

I don’t want you to think that Hero doesn’t help grow microgreens. So I added a little spoiler here.

Let’s get to the Microgreen Fertilizer Test with Genovese Basil

We are going to be much quicker with the basil test. You have seen how the process works. So I’ll show you the test’s start and end with basil.

Basil takes 30 to 50 days to grow, so it tests how well a potting mix can grow microgreens both with the fertility and water-holding capacity.

Here is where the fertilizer helped.

First off, the test procedure is the same, with the following exceptions.

Only one gram of Genovese Basil seed is used on each tray. 

Early waterings were the same, but as the test progressed after day 14, I could no longer water the microgreens on the same day because of differences in the soil composition and growth rates.

The Home Microgreens Potting mix is lighter with the addition of perlite, so it dried out quicker than the pure coconut coir.

The growth in each tray differed enough that some plants used more water than others because of the increase in leave mass.

Therefore, I went back to how I water my microgreens and only added water when the trays were judged to be dry.

Genovese Basil Out of the Blackout – Day 9

The video shows that the trays stayed moist enough, so they didn’t need water during the blackout period.

Nine days after planting, the basil microgreens are ready to go under the lights.

Notice that the basil microgreens on the pure coir are larger than those on the Home Microgreens Potting Mix.

using a microgreens fertilizer on basil microgreens
The two trays on the left are Home Microgreens Potting Mix; the right two are pure coconut coir.

The trays were watered with the same one-half cup of either tap water or Hero Plant Food at 25 to 30 milliliters per half gallon of water.

Skip to Day 30

Now we can see a huge difference in the microgreens grown in Home Microgreens Potting Mix and pure coconut coir and those that received Hero Organic Plant Food.

basil microgreens 30 days old using a microgreen fertilizer.

Reading the writing on the tape might be hard, so from left to right, the trays are in the following order, HM Potting Mix plain water, HM Potting Mix with Hero, Coir with Hero, and Coir with plain water. 

The Genovese Basil grown in the HM potting mix with tap water has more mass, but I believe that is the camera angle. 

The tray watered with Hero microgreen fertilizer has much larger leaves.

comparing basil microgreens using fertilizer with home microgreens potting mix.

You can also see that the basil grown in pure coir and watered with Hero is not quite as far along as those in the potting mix, but it is 1,000 times better than its compatriot that only received tap water.

Genovese Basil After 40 Days Using a Microgreens Fertilizer

After ten more days, there is even more of a difference. The trays that received Hero Organic fertilizer have grown quicker than those without fertilizer.

day 40 of the microgreens fertilizer test using basil as the microgreens

Is that to be expected, but until now, no fertilizer has improved growth in microgreens grown in Home Microgreens Potting Mix.

Ocean Solution grew better microgreens in coconut coir and mats made of hemp and bamboo, but not HM Potting Mix.

Basil grown in HM Potting Mix and watered with Hero Organic Fertilizer is taller and has much larger leaves than without. 

Also, the basil grown in pure coir and watered with Hero is almost as good as the potting mix without fertilizer.

Even Better on Day 48

basil microgreens after day 48

The basil has grown so much in the last eight days that you can’t read the labels. The leftmost tray is HM Potting Mix watered with Hero. The middle tray is pure coconut coir watered with Hero, and the rightmost tray is HM Potting Mix using tap water. 

Microgreens that grow longer than 15 to 18 days will most likely benefit by being watered with Hero Organic Plant Food. If you keep your microgreens in trays longer than 20 days, you will benefit by watering with Hero Organic Plant Food.

Whether it is basil, cilantro, peas, or lettuce that you cut and grow again, you will all benefit from using Hero fertilizer.

Home Microgreens Potting Mix

Home Microgreens Potting Mix has a guaranteed analysis of 0.45-0.18-0.40 derived from natural and composed products. 

It will grow any microgreen well without any additional fertilizers or additives. But as you saw, adding fertilizer might be beneficial once the one-month mark is reached.

But the potting mix doesn’t need any additives for most microgreens.

Why Doesn’t Pure Coconut Coir Grow Microgreens Very Well?

This article is long enough, but I want to discuss a little more on this subject. Here is a podcast that explains my views.

Hero Organic Plant Food

According to the label, Hero Organic Plant Food has a guaranteed analysis of 3-2-2 and is derived from food materials. 

It’s labeled as organic (I didn’t see a certified organic symbol), sustainable, pesticide-free, and made in the USA. 

I like that it is made from recycled food.

As the video mentioned, watering a Home Microgreens Tray costs about 5 cents, and less than 20 cents to water a 1020 tray. That is very reasonable.

I found that it mixed very easily in water. I added some water to the container, added the correct amount of concentrate, then filled the container the rest of the way with water. 

You must add the water slowly as the mixture will foam and bubble up with a stream of water, but it quickly dissipates.

There is a slight earthy odor. It is not a bad or strong smell, and the odor did not last or linger in the house. My dog was interested in the smell, but Caden is always curious about anything I do. He did not bother any tray or plant, only sniffed at it.

After you add water, the mixed product must be used and not stored. 

Hero Plant food can also be used in the garden or on houseplants. It can also be used to foliar feed flower beds and landscape plants.

I would not recommend using this fertilizer if you are watering over the top of your microgreens. 

You should not be watering in this manner anyway. 

Be sure to water at the soil surface or in a watering tray below the planting tray.

I Recommend Hero Organic Plant Food to Bottom Water Microgreens

As the images show, Hero Plant Food will improve the growth of any mid to long-growing microgreen.

You can purchase Hero Organic Plant Food at Nature’s Lawn & Garden. This is not a sponsored article; I currently have no affiliate partnerships with them. 

I do, however, recommend their product.


  • 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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