Effective Microorganisms

Dr. Teruo Higa started studying microorganisms in the 1960s and 1970s, mostly at Ryukyus University in Okinawa, Japan.

By the early 1980s, he was perfecting his liquid culture of specific “facultative anaerobic microbes” that provide amazing benefits when combined together in specific proportions.

KefirKefir is also made with fermenting microbes.

Facultative anaerobic means microbes that can live both in air with oxygen and also in low oxygen conditions.

They’re also called fermenting microbes and some of them are responsible for making your bread, beer, wine and yogurt.

Facultative anaerobic products have various brand names. Effective Microorganisms, or EM, is actually trademarked by one company.

Other companies have given it other names. I encourage you to use any brand as long as it’s manufactured based on the research of Dr. Higa, with the microbe species in the correct proportion to one another.

[Update: I now sell one such brand here.

I will refer to all of these products as EM here, but I’m not affiliated with any of the companies that make it, and my directions on how to use the product may differ from theirs.

There are up to 20 different microbes in the inoculant from all over the world, but when we put them together, the magic begins.

It’s not something you can do at home, but you can buy the inoculant from a manufacturer with the equipment and knowledge to put them together in exactly the right proportions and under the right environmental conditions.

The three groups are lactic acid bacteria, yeast and photosynthetic bacteria, plus some other wild microbes that will be let into the brew.

Not that it’s particularly important to us gardeners, but here’s how the three different classes work together. I’m sure it’s more complex than this, but here are the basics.

The lactic acid bacteria make up the majority of the population. They protect the other two groups by producing acids that control harmful microbes and enhance organic matter breakdown. They can even help fungi to break down difficult-to-digest lignins and cellulose.

The yeasts produce hormones, enzymes, vitamins, and antimicrobial substances that manipulate their environment and protect the photosynthetic bacteria, also known as phototrophic bacteria.

The photosynthetic bacteria can, yes, photosynthesize. They can actually fix both nitrogen and carbon from the atmosphere.

Photosynthetic bacteriaChloroflexus aurantiacus is a photosynthetic bacterium isolated from hot springs (not a component of EM).

While all of the microbes in EM are important, these guys are considered by Dr. Higa to be the “heart of effectiveness” of the group.

They supply amino acids, nucleic acids, sugars, and other bioactive substances, some of which they feed to the others. They break down lignins and even decompose toxins and convert them into nutrients.

More important than all of this is how they work together and provide for each other to contribute a host of benefits to our gardens. They create an abundance of antioxidants, controlled breakdown of organic matter, and according to some people, an extremely positive energy force.

Really, I think of them as providing all of the same benefits as the other beneficial microbes I hope to house in my garden, but they just happen to be exceptionally good at it when they get together. Take any of them out or even change the proportions in the mix too much, and you no longer have EM or the same benefits.

EM was originally developed and used in agriculture where it was found to improve compost and soil organic matter breakdown. It was even found to have a beneficial effect on other microbes in the soil, coaxing them to get to work.

It isn’t as well known in the United States or Canada yet, but it’s used in over 150 other countries and there have been thousands of trials showing its effectiveness.

After its value was seen in soil and composting, EM started to be used in other areas with astounding results. It has helped plants beat diseases such as Botrytis, insects such as weevils and other stressors.

Like compost tea, it’s not a pesticide and can’t be marketed as such. It simply creates health in the plant and helps to outcompete predators.

It also helps crops achieve higher brix and longer storage. One study sticks in my mind because a 50% increase in yield was obtained just with EM.

It’s also been found to have uses with animals. Initially, with livestock, they found it helps to control odors, diseases and insects when sprayed in the air and on the animals in barns. It also acts as a probiotic for animals as part of their water and feed.

It cleans polluted water and can actually make dirty water drinkable.

EM ballsEffective microorganism balls are used for cleaning up wastewater.

It has been used to clean up part of the ocean in a bay in Japan. If you go on the Internet, you can find pictures of groups of Japanese people standing by rivers, all dumping their EM into the river to clean it up.

It is also used to clean septic systems and sewers, where it reduces odors, toxic gases, sludge, pathogens, nitrates and phosphates and ties up heavy metals. If you have a pond, you should spray it with EM to get the microbes in there and even control mosquitoes.

Of course, it wasn’t long before humans tried drinking it.

In my opinion, it’s probably one of the best probiotics in the world. Not only have I been using it myself for many years, but when I used to sell it, I had many clients get amazing health benefits from taking it — even people with irritable bowel syndrome and other digestive issues.

When I look at some of the other probiotics on the market, I see many of them have most of the same microbes, but EM has the photosynthetic bacteria, and I believe that’s what sets it apart.

Plus, it’s often much cheaper than many of these other products. I used to sell a one-quart food-grade version mixed with organic herbs for about $50. I’ve read stories of some health practitioners charging hundreds of dollars for a bottle because it works so well.

While I certainly can’t tell you to do this because it’s not food-grade, I just drink the regular stuff that’s brewed for horticulture. That costs half as much, or if “activated” first, the cost goes down to a couple of dollars per quart. You’ll learn how to activate EM shortly.

People have found many other uses for it, too, as a deodorant, toothpaste, in skin care products, and for cuts and sores. In fact, some people have miraculously cured eczema and other skin problems by externally applying EM.

It’s used to wash fruits and vegetables, as an additive in the laundry, and for general odor control. It even does a decent job of removing rust.

Odor controlWhy not?

I know all of these things work because I’ve been doing them for years. EM is now starting to be used in garbage dumps, for disaster relief, for soil remediation, to clean hospitals, and has the potential to help out when the next petroleum company spews oil all over our oceans.

Of course, EM is not a magic bullet and results vary depending on many environmental factors, but I have found it can work some miracles, sometimes very quickly and sometimes only when used consistently over a number of months.

Making Activated EM

ChloramineMonochloramine is one of several forms of chloramine. Chloramines are formed when ammonia is added to chlorine to treat drinking water. It’s also what makes the “chlorine-y” smell at the pool.

You can’t make EM yourself unless you want to spend tens or hundreds of thousands of dollars to set up a lab and get the proper strains of microbes, but you can buy an existing mother culture from a supplier and multiply that, much like you would make yogurt. The process is called “activating.”

Unlike yogurt, which you can keep going forever, EM can only reliably be activated once, maybe twice, and then you need to get a new mother culture. This is because the microbes need to be in specific proportions, and will move away from this with each activation.

You can definitely do it once, making five gallons of good activated EM from one quart of mother culture. This is done both to save money and to wake up the microbes that may be dormant if the mother culture has been around for a while.

Dechlorinated water is actually not necessary, but definitely beneficial because chlorine kills microorganisms.

Tap water can be dechlorinated by letting it sit out for 24 hours, unless your city uses chloramines, in which case humic acids or ascorbic acid should be added.

Here are my instructions: How to make effective microorganisms

Using EM

EM is preferably applied in smaller doses, more often. Like compost tea, it could be daily, weekly, monthly, or seasonally. Application rates are the same for EM and activated EM, the most common suggested rate for agriculture being 1 to 10 gallons per acre per year, which is approximately 6 tablespoons to 2 quarts per 1,000 square feet per year, spread out over as many applications as are feasible.

Lots of EMThis is enough EM to inoculate a large area. Each bottle should be filled to the top if kept for long-term storage.

For some reason, the application rate given for gardens is 1 gallon per 1,000 square feet per year, which is nearly 44 gallons per acre per year, and the suggestion is generally 1 pint per application.

I’ve done a lot of research and never figured out why this discrepancy exists. It may be that it’s just more economically feasible to apply it at a higher rate for small areas, whereas it would get expensive on a big farm. It may be because a garden is considered a higher-value landscape, or it may be just a marketing thing.

After extensive research into studies that have been done in agriculture, I go for the high end of the agriculture rate and use 10 gallons per acre per year, which is close to 2 pints per 1,000 square feet per year.

More importantly, I generally spread this out into 1/2 cup per 1,000 square feet per month from early spring through late fall.

I may not get to the 2 pint total, but it’s more important to me not to use too much EM and to achieve a sufficient dilution. If you only want to spray three times each year, I still recommend you go for this 1/2 cup per 1,000 square feet rate.

Please keep in mind that more is definitely not always better.

Several research trials have found that 2 teaspoons per 1,000 square feet to be more effective than higher doses. Another study found powdery mildew control at 0.4 teaspoons per 1,000 square feet.

If too much EM is applied, studies have found that organic matter may break down too quickly and the soil may become compacted. For all of these reasons, I believe one pint per 1,000 square feet is too high for one application in many gardens.

I usually end up diluting it 1:200 with water, or at a bare minimum 1:100, which would be one to two teaspoons of EM per quart of water.

It’s technically supposed to be 1:500 or even 1:1,000, but that’s a lot of water and pretty much impossible with a backpack sprayer. Despite the cold water not being the greatest for the microbes, a hose-end sprayer works really well for this because you can just set the ratio on the dial and spray.

Pressure sprayerYou can use a hand-held pressure sprayer, if you don’t like using the backpack type. You may need to use a lower dilution ratio, or refill it a bunch of times.

This ratio also depends on the frequency of application and the area you’re trying to cover.

For example, daily use through irrigation systems often use very diluted ratios such as 1:10,000. Use on turf and in gardens might be more like 1:100, basically to provide adequate coverage, and then watered in with a sprinkler.

Some sources say not to apply it directly to flowers or newly seeded areas, as this could potentially ferment the flowers or seeds. I’ve rarely found this to be a problem, but it is something to watch out for.

Once your EM or activated EM has been diluted in water — often referred to as “extending” the EM — and mixed with any optional biostimulants, it should be used within a few hours.

It’s generally recommended to mix it again with equal parts unsulfured molasses, even though this was also done during the activation stage. This gives the microbes some sugar to work with when they get into the garden.

MolassesMolasses makes great microbe food, and contains minerals as well as sugars.

I also apply it with the biostimulants discussed in an upcoming article, most commonly some mixture of sea minerals, kelp, fish and humic acids.

EM can also be sprayed on compost, ponds, and buildings, and even on pets and livestock. It’s entirely safe for people and animals to enter the areas after spraying.

You can see that EM provides many of the same benefits as compost tea, but it’s different. It’s a mixture of only a handful of species of mostly facultative anaerobic microbes, but they just happen to be very important species, especially when mixed together in the right proportions.

The shelf life is quite long and the quality of the product is fairly consistent.

With compost tea, on the other hand, we’re going for maximum diversity, with as many different species of aerobic and facultative anaerobic microbes as possible. The shelf life is very short and the finished product more variable. Incidentally, I always put some EM in my compost tea when I’m brewing, at two tablespoons per five gallons.

This is not only to make sure those microbes are there, but more to hopefully fill up any anaerobic pockets with these facultative anaerobes that can live there.

I generally recommend EM over compost tea as a starting point for most gardeners because it’s much less expensive and easier to get started. I use both and the serious gardener may eventually want to, as well.


  • EM is a liquid mixture of relatively few mostly facultative anaerobic microbes in specific proportions. You can buy a bottle here.
  • EM is used for soil, composting, plants, water, buildings, animals and people.
  • EM can be “activated” kind of like yogurt by fermenting it with molasses, water and other optional ingredients, making over 5 gallons from 1 quart of mother culture.
  • EM is mixed with 100-1,000 parts water and applied to plants and soil at a rate of 1/2 teaspoon to 1 pint per 1,000 square feet, weekly, monthly or seasonally, often mixed with biostimulants (I use 1/2 cup of EM monthly).
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