Getting started with effective microorganisms (EM): 7 golden rules for success

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Effective microorganisms (EM) are easy to use, but they're living organisms. Chlorinated water, a poorly rinsed sprayer, or a jug left out in full sun is enough to weaken them. Most disappointments come from these small mistakes, far more than from the product itself.

Here are the golden rules we recommend before you use EM for the first time, whether in the garden or around the house. They apply to EM-1, Microferm, and most of the liquid products in our lineup. For exact doses, your product's label is always the final word.

1. Use non-chlorinated water

The chlorine in tap water is there to keep microbes in check, and it does the same to the microorganisms in EM. Manufacturers list it among the incompatibilities, and our own activator recipe points it out too: chlorinated water can prevent fermentation.

• Rainwater is ideal, as long as it's clean and stored away from light.
• Tap water works if you let it sit for 24 hours in an open container: chlorine is volatile, so it evaporates. The larger the surface, the faster this happens.
• Water filtered through activated carbon also works.

Some water systems disinfect with chloramines, which are more stable and don't evaporate. If in doubt, check with your water utility or use rainwater. Use lukewarm rather than cold water for activation, and never hot water.

Emy's tip

Always keep an open watering can or jug of tap water next to your EM products. That way, on the day you need it, your water has already had time to sit.

2. Never mix with bleach, disinfectants, or fungicides

The technical data sheets are clear: bleach, chlorinated water, bactericides, fungicides, and oxidizing products reduce the survival of the microorganisms. Mix the two, and one simply cancels out the other.

• Never pour an EM product into the same tank as a chemical treatment product.
• Keep a sprayer just for EM, or rinse it thoroughly with clean water before use.
• After cleaning with bleach, rinse the surface and let it dry before using an EM cleaner.

Choose food-grade plastic or glass containers: EM solutions are acidic and can corrode some metals.

3. Dilute correctly

An EM solution is very acidic, with a pH of around 3.5. Undiluted, it can damage roots and foliage, so it's almost always diluted. Here are the most common guidelines, based on the manufacturers' instructions:

• Watering soil and plants: 1% for Microferm, which is 1.3 fl oz per gallon (10 ml per liter), or 3.4 fl oz (100 ml) in a 2.6-gallon (10-liter) watering can.
• Seedlings and young plants: more diluted, around 1:500, which is about 0.25 fl oz per gallon (2 ml per liter).
• Animal litter and bedding, chicken coops, kennels: 1.3 fl oz per gallon of water (10 ml per liter) as a spray.
• Cleaning with EM Clean: from 1% to 10%, depending on the surface.

These figures vary from one manufacturer to another: for watering, you'll find dilutions ranging from 1:100 to 1:1000. Always follow the one for your product, and mix your solution right before you use it.

Did you know?

A "1:100" dilution means one part product to one hundred parts water. An easy way to remember it: 1:100 is a 0.34 fl oz (10 ml) capful in about a quart (1 liter) of water; 1:500 is the same capful in 1.3 gallons (5 liters).

4. Go for small, repeated doses

Professor Teruo Higa recommended several small applications rather than one large one, and the product instructions follow the same principle: increase the frequency, not the dose. This advice comes from the manufacturer and hasn't been tested in independent trials, but it makes sense: overdosing wastes product and increases acidity, with no proven benefit.

In practice, it's better to water the vegetable garden every two weeks at the right dilution than to pour on about a quart (1 liter) of nearly undiluted product all at once. In the garden, apply preferably in cloudy or damp weather, in the morning or evening, since the microorganisms don't handle full sun and drought well.

5. Store somewhere cool, away from light and frost

• EM-1 keeps between 37 and 100 °F (3 and 38 °C), ideally at a stable room temperature, in a dark place, with the cap closed. The date printed on our bottles is the expiration date (about two years after manufacture); other producers state about six months, so go by the date on the label. It must never freeze.
• Microferm in Bag-in-Box keeps until the expiration date printed on the packaging (about one year after production), because the pouch doesn't let air in.
• A home-activated solution should be used within 1 to 2 months of being made.

A slightly bulging bottle or a whitish film on the surface is normal: it's a living culture. A distinctly rotten smell, on the other hand, means the product has gone bad. We cover these signs in detail in our guide storing your EM and diagnosing a failed EM-A. Keep your products out of the reach of children and avoid contact with the eyes; in case of splashes, rinse with clean water.

6. Be patient and compare with a control area

Some effects show up quickly, like a litter box that smells less. Others, in the garden, are slow and subtle, and published studies show that they don't always appear. The best way to find out whether EM does anything for you is to run your own trial:

1. Choose two similar beds or rows (same soil, same sun exposure, same plants).
2. Treat one with EM and water the other with the same amount of plain water, without EM.
3. Write down the dates, take photos, and compare what matters to you: germination, vigor, harvest.
4. Repeat for a second season before drawing any conclusions.

Key takeaways

A control area is worth more than any testimonial: it's the only honest way to find out what EM changes for you, in your soil and with your gardening habits.

To see what trials carried out elsewhere have shown, check out our guide what science says about EM.

7. The most common mistakes

• Using tap water straight from the faucet, without letting it sit.
• Spraying an undiluted activated solution on leaves or seedlings.
• Storing the jug in a car, a greenhouse, or an uninsulated shed, where it gets hot in summer and freezes in winter.
• Reactivating an already activated solution to keep making more indefinitely: the manufacturer only intends one activation, and there's no guarantee the mix stays balanced in later generations. Start again from the mother culture, as explained in our guide activating EM-1 step by step.
• Expecting EM to make up for poor soil: it works alongside organic matter, it doesn't replace it. In the vegetable garden, use it with compost, mulch, or bokashi (see EM in the vegetable garden).
• Using a product for something it wasn't designed for: a garden or household product should never be used in the kitchen, or in animals' drinking water without veterinary advice.
• Opening a bokashi bucket too often: every time you open it, air gets in, and air is the enemy of fermentation.

To get started with no preparation needed, Microferm EM-A is the simplest option for the garden, and EM Clean for the home. If you're not sure which product to choose, our guide choosing the right EM product will help.

In summary

To succeed with EM: use non-chlorinated water, never mix with bleach or treatment products, dilute according to the label, apply small repeated doses rather than one large one, and store somewhere cool, away from light and frost. Finally, compare with a control area so you can judge for yourself. These simple habits prevent the vast majority of failures and help you get the most out of your products.

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