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Aerated Worm Tea

Updated: Sep 16, 2021

worm tea in a clear pitcher

While you don't want to pour this kind of tea over ice, worm tea is a nourishing drink for your soil and plants! In addition to suppressing pests and diseases, worm tea has shown to be effective at stimulating plant growth and increasing nutrient uptake.

There are two types of worm tea: aerated and non-aerated. Non-aerated tea transfers the benefits of worm castings to an aqueous extract over the course of 14 days and requires little more than a bucket, some worm castings, and a stocking. Every now and then, stir or agitate the mixture, and two weeks later...voila.

But by aerating the tea over the course of 12 - 48 hours, the benefits of worm castings are boosted by mixing in oxygen and increasing microbial populations. The resulting tea is concentrated with all the good things we love about worm castings, and can be poured over soil or sprayed on your plants' foliage for faster results. Both aerated and non-aerated teas are easy to make and to use, but you'll need a few extra items to get started with aerated worm tea.

You'll need:

- an aerator (an inexpensive aquarium bubbler is fine, or you can opt for a professional tea aerator)

- mesh bag (or stocking)

- 5 gallon bucket

- 2 cups high quality worm castings

- non-chlorinated water

While a professional worm tea kit isn't necessary, it is convenient! If you think you'll be making tea several times per season, it's worth looking into a kit if ease of use is important.

Make sure all components are clean and do not contain residuals from your last brew.

Quality Worm Castings

Place two cups of high quality worm castings into a mesh bag or stocking and tie off. The water should easily flow through the castings but the castings shouldn't seep out of the bag during brewing.

The quality of the castings will directly impact the quality of the tea extract. If the worm castings you start with are deficient in nutrients or microbes, your tea will also be deficient.

You may use supplements such as kelp or rock dust to increase nutrient content. A half castings/half compost mixture creates a tea with diverse microbial and nutrient content. It is not recommended to add any sugars, such as molasses, to your tea mixture. Although the addition of molasses will initially boost microbes, the spike in population will quickly deplete available oxygen and ultimately cause microbes to die (creating toxic conditions in the tea).

Non-chlorinated Water

Chlorine will kill any beneficial microorganisms in your tea during the brewing process. We recommend using water from a natural source such as rain or pond water. Water collected from nature won't have any chemical treatment and will contain natural bacteria, offering the perfect conditions for microbes to proliferate. Non-treated well water will also work.

If you have access only to municipally treated water (ie tap water), fill your bucket and allow it to set for 24 - 48 hours. During this time any chlorine in the water will off-gas.

Water should be kept at 70-75 degrees Fahrenheit for the duration of your brew. Bear this in mind when choosing your brew location.

Location of Your Worm Tea Brew

Be sure to choose a location that can accommodate your brew for up to two days. The location you choose may be indoors or out, but be sure it is protected from direct sun or unexpected rain showers. The water should be kept consistently at 70-75 degrees F, so during summer heat an indoor brew may be advisable.

After positioning your aerator in the bucket, add your mesh bag of worm castings and secure them to the handle of the bucket using a carabiner. This ensures the bag will not fully submerge or accidentally slip down into the water.

How Long to Brew Worm Tea

Let your tea aerate for no less than 12 hours, but no more than 48 hours.

As it brews, the water will begin to change from clear to brown.

Check water temperature periodically to ensure it's within the optimal range of 70-75 degrees F. Routinely check all parts to make sure everything is secure and working properly, and that there's no unwanted leakage or splashing.

Use tea immediately after brewing, optimally within four hours. If you are using only some of the tea at a time, let the remaining tea continue to aerate until you are ready to use it. Once the tea has stopped aerating, its microorganisms will begin to die. Unused tea may be stored in refrigeration for up to 14 days.

Using Worm Tea - Foliar Spray

If using in a sprayer, be sure to pour the tea through a cheesecloth or fine mesh stocking to remove residuals from the aqueous solution. Otherwise tiny particles could clog your spraying mechanism.

You may use your worm tea at full strength, or dilute it with water for a lesser concentration. Mix one gallon of worm tea with four gallons of water for a 20% vermicast tea spray.

Mist foliage during the morning hours, after any dew has evaporated but before the sun is overhead. This allows foliage to dry before the heat of the day.

The worm tea spray will coat the leaves and stems of the plant, repelling garden pests and inhibiting plant pathogens.

Using Worm Tea - Soil Drench

If using in a watering can, no straining is required.

Again, you may choose to use your worm tea at full strength, or dilute it with water for a lesser concentration. One gallon of worm tea mixed with four gallons of water makes a 20% worm tea solution.

Pour onto the soil around the drip line of the plant or pour right over the top of the plant, drenching the leaves right down to the soil.

Worm tea affects plants faster than worm castings that are mixed into the soil, so you'll reap its benefits almost immediately.

When to use Worm Tea

- For best results, apply worm tea every two to four weeks during the growing season.

- Avoid spraying worm tea when the sun is high and direct; microbes will be lost to ultraviolet radiation

- Spraying in midmorning will allow foliage ample time to dry, reducing risk of foliar burn

- Overcast days are the perfect time for spraying

- If rain is forecast, wait until after it rains to eliminate wash and reduce dilution in the soils


- Thoroughly cleaning your equipment at your brew's completion is vital. Equipment that is stored unclean can grow toxic bacteria, contaminating your next brew.

- Empty your mesh bag's spent worm castings into your garden; it is full of microbes!

- Thoroughly rinse out the mesh bag, turning inside out to be sure all unseen castings are removed from crevices.

- Flush water through any hoses or other submerged parts before bacteria can accumulate in inaccessible places in the equipment.

- Rinse out the bucket.

- Allow all items to thoroughly dry in the sunshine.

- Store your rinsed, dried equipment inside, away from extreme weather conditions for longevity.

Until next time...happy growing!

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