Tips For Using Compost Tea – How Do I Apply Compost Tea To My Plants

Tips For Using Compost Tea – How Do I Apply Compost Tea To My Plants

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By: Bonnie L. Grant, Certified Urban Agriculturist

Most of us have heard of the benefits of compost, but do you know how to use compost tea? Using compost tea as a foliar spray, drench or simply added to houseplant water provides quick, easy-to-uptake nutrients in a gentle, organic manner. It is one of the easier fertilizing methods and can even be made from household items like kitchen scraps. Further reading will introduce you to compost tea applications and other tips.

Benefits of Compost Tea

Whether you have local yard waste recycling or are a DIY composter, compost is useful as a soil amendment. Making compost tea dilutes the nutrients, making them easier for plants to use quickly. It also reduces the possibility of harm from synthetic preparations and ensures an organic feeding. The tea may also help ward off some diseases and pest problems. Knowing when to apply compost tea and how to mix it will ensure plants get the boost they need.

Using compost tea can deliver powerful health benefits to most plants. It introduces good microbes that can overtake the bad microbes which cause disease. Regular use will increase these benevolent microbes, boosting overall soil health. It also helps soil retain water, reduces fertilizer usage and attendant salt accumulation, and improves soil pH to levels that encourage nutrient and moisture uptake by plants.

Teas made from compost that is primarily plant based can be used nearly daily if necessary. Those with a high nitrogen content, such as composted manure, can still burn plants and should be applied no more than once per month in a heavily diluted state.

When to Apply Compost Tea

The optimum time of day to apply compost tea is in the morning, when plant stoma are open to receive it and the sun will dry leaves and prevent fungal diseases from excess moisture. Apply when soil is moist if using the product as a drench.

For most ornamental plants, spray in late winter to early spring and again when leaf buds break. For annual beds, use tea prior to planting to boost beneficial microbes. If you experience fungal or insect issues, apply the tea immediately and at each regular watering period.

Even houseplants benefit from compost tea application. Use well diluted by at least half at normal irrigation periods.

How Do I Apply Compost Tea?

Making the correct mixture that is a balance of the compost and water is an important first step. Compost tea can “brew” in either an aerobic or anaerobic state. The non-aerated tea is mixed in a container with water and allowed to ferment for 5 to 8 days. Aerated teas are ready in 24 to 48 hours.

You can make these by suspending the compost in a burlap sack over a container and showering it with water, letting the leached solution drip into the container. Spray the mixture onto plant leaves or drench the soil around the root zone. Teas may be used full strength or diluted at a ratio of 10:1.

Apply 5 to 10 gallons per ¼ acre for larger situations (approx. 19 to 38 liters per .10 hectare) when using the fertilizer for root drenches. Large area foliar sprays should use 5 gallons per 2 acres (about 19 liters per .81 hectare).

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Read more about Composting Basics

Compost Tea Ingredients

Compost Tea Ingredients and Biological Food Sources

Compost your #1 ingredient

High quality compost, possessing a full-diversity of biology, is the key to brewing quality compost teas. Different food sources and techniques used to produce the compost will offer differing results. For example, bacteria generally dominate vermicompost whereas fungi tend to be the primary organism in forest humus and mushroom compost.

Ensuring that proper biology is active or at a minimum present in your compost is necessary to achieve the desired results from brewing compost teas. Either purchase compost from a source willing to provide biological assessments of their product(s) or have your own compost tested. Testing your home produced compost is a useful tool in assessing the life in your compost and the potential benefits of your compost teas. Biological assessments or working with your own microscope is the only means to ensure that the full diversity of biology is present in compost or compost teas.

  • For a list of biological Testing Labs visit:

Earthworm compost / Vermicompost contains a high percentage of earthworm cast or worm manure and significantly large populations of beneficial bacteria, enzymes and protozoa. Earthworm composts usually contain lower levels of active fungi, yet should possess plenty of dormant fungi spores that can be encouraged by pre-treating the vermicompost with sources of food for fungi and allowing the compost to mature for 3 – 7 days prior to beginning your brewing cycle. (More on pre-treating below)

Forest Humus:

Harvested from deep forests floors and rich in diverse types of fungi. Forest humus is an excellent source of biology for use in fungal dominated compost tea blends.

Mushroom Compost:

Derived from the remnants of mushroom manufacturing and also a source of more fungal dominant compost, yet not all mushroom composts are created the same. Some commercial mushroom growers sterilize their compost prior to reselling, ask for biological testing results or have mushroom composts tested.

Pre-treating Compost to Balance or Increase Fungal Biomass

For 5-gallon brewers:

  • Place 2 – 4 cups of compost in a plastic container (for best results gather from different sources)
  • Apply ¼ cup of organic oat flour or finely ground oatmeal across the compost and turn-under
  • Mix the recommended liquid ingredients with ¼ cup of water
  • Apply the mixture evenly to the surface of the compost
  • Cover with a loose fitting lid or moist cardboard and store in a cool dark place for 3 – 7 days

Pre-activation times can vary based upon the presence of active fungi, dormant spores, moisture and temperature. Under the right conditions you should see a white fuzz (fungi mycelium) begin to cover the surface of the compost within 3 – 7 days. This is an indicator of active fungi and will tell you that your compost is now ready for brewing into tea. Use this pre-treated compost in your Garden Tea Brewer.

How to Make Your Own Compost for use in Compost Tea

Composting with red worms is one of the easiest means of creating a high quality, compost. Under the ideal conditions this can be achieved in as little as 60 - 90 days.

Using 35% dry brown materials, 35% fresh green materials, and 30% manure can create a more biologically balanced compost.

Fungal-dominated compost can be made using 45% dry brown materials that should include wood chips, 30% fresh green materials, and 25% manures.

Building your compost heap:

  • Create a 3” – 4” layer of materials
    • Apply a thin layer of steel cut oats
    • Water each layer with a good balanced compost tea
    • Repeat until your heap is 4’ x 4’ x 4’
    • Cover your heap with a large sheet of wet cardboard to shed excessive water
      • You may need to weigh-down the cardboard to keep it in place.
      • Turn compost heaps 2 – 3 times over a 3 month period or allow it to age 6 – 9 months
      • Turn one last time and then allow to mature for 3 weeks

Microbial Food Sources

Simple sugars serve as an excellent bacterial food resource. All of the sugars listed above also contain trace minerals, which will help to fortify teas with micronutrients. When using molasses be sure to use unsulfured molasses.

On its own, kelp is an excellent fertilizer and biological stimulant containing growth hormones such as auxins, gibberellins and cytokinins, which are highly beneficial to plants and soils. When used in compost teas, kelp encourages growth of fungi and bacteria. Kelp is a naturally rich organic source of Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), Sulfur (S). Kelp contains at least 60 trace minerals, over 12 vitamins, a variety of amino acids. Soluble seaweed powders are more concentrated and require lower quantities than kelp meals.

Fish hydrolysate is a cold processed and enzyme digested liquid fish fertilizer made from all fish parts. Fish hydrolysate is used as a standalone protein-rich fertilizer and to stimulate both bacteria and fungi. Pre-treating compost with Fish hydrolysate will help increase the fungal biomass.

Humic Acids:

Humic acids are primarily found in manure, peat, lignite coal, and leonardite a highly oxidized form of organic matter and the source for most humic acid products. Humic acids work great as a food source for all beneficial microorganisms in compost tea. Use to pre-treat compost and increase the fungal component in your tea. Humic acids have been shown to increase seed germination rates, aid in breaking up clay and compacted soils, support the transfer of micronutrients between soil and plant, and improve water retention within soils.

Grain Meals and Flours:

Oatmeal or oat flour is an excellent and cost effective fungal food resource and can be added directly to compost tea. Fungi feed on the proteins and complex carbohydrates using the fiber as a physical attachment point for fungal spores and hyphae. Though oatmeal and oat flours are preferred, other grain meals such as wheat, rye, or barley may be used.

Soft Rock Phosphate is one of the best natural sources of phosphorus (P) and calcium (Ca). When applied to soils Colloidal Phosphate is immediately available to plants and will act as a long-term source of phosphorus. In compost tea soft rock phosphate is used as a fungal food source.

Glacial Rock Powders and volcanic ash deposits such as AZOMITE ® (a mined volcanic ash deposit) contain a broad spectrum of metabolically active minerals and trace elements. These concentrated mineral powdersare used to fortify teas and ensuring the presence of micronutrients. These powders can also be used to re-mineralize soils or as a livestock nutrient supplement.

Teas made from Alfalfa meal serve as a standalone fertilizer. As an additive to compost tea, alfalfa serves as food source for both bacteria and fungi. Alfalfa is a good source of vitamins A and B Folic acids, Amino acids, crude proteins, natural sugars and starches along with Nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulphur (S), Manganese (Mn), iron (Fe), copper (Cu), boron (B), and zinc (Zn) . Alfalfa Meal as an organic garden fertilizer has an approximate N-P-K analysis of 2-1-2.

For centuries bat guano has been recognized for its outstanding effect on agricultural crops. Bat Guano provides both macro and micronutrients along with active and dormant microorganisms to soils. Applications of Bat Guano in dry forms or brewed in garden teas can provide an outstanding organic fertilizer without increasing salt content or acidity.

SEA-90 is 100% natural sea mineral solids containing 90 essential micronutrient elements. SEA-90 is the product of 30 years of research by Maynard Murray, MD who proved soils enhanced with sea minerals grow crops superior to that grown solely with conventional fertilizers. SEA-90 is a water soluble, mined sea mineral for use in organic food production and as a livestock feed supplement.

Mycorrhizal Fungi

Mycorrhiza describes the mutually beneficial relationship between a plant and root fungus. More than 90 percent of plant species in nature form a symbiotic relationship with the beneficial mycorrhizal fungi.Mycorrhizae bond with the roots of a host plant and exchange valuable nutrients and minerals with one another. Mycorrhizal fungal filaments extend far into the soil and act as extensions of the root systems mining water, minerals and nutrients more efficiently than roots alone greatly expand a plants absorption capacity. Add mycorrhizal fungi spores at the end of a brew cycle and prior to application (mycorrhizal fungi should be applied as a soil drench

Insect Frass 2-2-2 is an organic fertilizer and soil amendment derived from the excrement of herbivore insects, providing high quality nutrition for plants and soils.

Insect Frass has the added benefit of acting as a natural bio-pesticide/ biological defense. Insect Frass contains high concentrations of Chitin (pronounced “Kite-in”). When plants sense chitin concentration in the vicinity, they respond as if they are being infested and eaten by insects. The presence of chitin triggers an "auto-immune" response in plants causing the plant to defend itself from pests and pathogens. Plants begin to protect itself by strengthening its cell walls, producing more chute biomass (stalk and leaf material), and excreting secondary metabolites to ward off pests and pathogens. As a natural bio-pesticide chitin and chitosan has been recognized to help defend plants against botrytis (grey mold), powdery mildew, early and late blight, fungal pathogens in the root zone (root rot) and root-feeding nematodes.

Chitin is a naturally occurring molecule ( Poly-N-acetyl-D-glucosamine). Structurally, chitin is related to cellulose, which consists of long chains of glucose molecules linked to each other. Chitin is present in the shells of all crustaceans and insects, and in many fungi, algae, and yeast.

To make a batch of basic compost tea with worm castings, all you really need to do is soak some vermicompost overnight in water. I prefer to use something as a makeshift tea bag because it makes it less messy but it is not necessary. Here is the basic worm compost tea recipe that I use.

  • Find something to use as a compost tea bag (old t-shirt, panty hose, cheese clothe, etc). For more about compost tea bags read: What to use as a Compost Tea Bag
  • Fill your homemade tea bag with worm compost and tie off the open end of the tea bag somehow.
  • Submerge the worm compost tea bag in a bucket of water. I use a 5 gallon bucket but any size bucket will work.
  • Let it sit overnight. In the morning the water should be light brown.
  • Because the beneficial microbes in the worm compost tea will start to die off, water your garden first thing in the morning for best results.
  • Remove the worm compost tea bag from the bucket, cut it open and add the worm compost either to your garden, your worm compost bin, or your hot compost pile.

This Kitchen Sink Compost Tea Helps Your Plants Grow Big and Strong

You know you’re a true plant parent when you’re always looking for new ways to help your indoor jungle grow big and strong. The answer, however, doesn’t always have to do with how much light or water they’re getting. Karina Aldredge, founder of Sacred Elements, says the key to big, strong, healthy plants is a mixture of organic materials you might normally add to your compost.

Aldredge’s kitchen sink compost tea might not look appetizing to you, but it definitely does to your plants. It involves four different types of food waste: peels from bananas, the skins of onions, eggshells, and ground coffee bits. Instead of adding these food scraps to your compost, you let them soak—or, umm, steep?—in a pitcher of water or glass jar.

Like a homemade fertilizer of sorts, you can think of compost tea as a plant’s vitamins. It has been known to improve plants’ soil health and also boost their immune system, if you will, so that they can better fight off pests and disease. “Add banana peels, onion skins, eggshells, and ground coffee,” Aldredge says in a TikTok. “Let it steep in water for three to five days and add it to your water for your houseplants and garden.”

While steeping, some of the nutrients and microorganisms will leach from the composted organic materials and into the water. While the nutrient content from steeping is generally low, the microorganisms from the compost materials can really help a plant’s overall health, preventing root rot and other diseases. The microorganisms found in compost tea are also thought to better aerate plants and improve their water retention, ability to absorb nutrients, and soil structure. Pretty impressive, huh?

If you want to make Aldredge’s compost tea for plants, follow her simple instructions below.

How to Make Compost Tea for Plants

Banana peels
Onion skins
Coffee grounds

1. Add scraps of banana peels, onion skins, eggshells, and ground coffee bits to a glass jar or pitcher.
2. Once the jar or pitcher is full of your compost scraps, fill it the rest of the way up with water.
3. Steep in water for anywhere from 3 to 5 days.
4. When the kitchen sink compost tea is properly steeped, strain the liquid. Then, water your plants with a 1:4 ratio of one part compost tea to four parts water.
5. Blend up the banana peels, onion skins, eggshells, and coffee grounds with water to create a compost smoothie. Use it to fertilize your garden.

The Top Benefits of Compost Tea

Compost tea is a biological fertilizer for the garden. Gardeners all around the world are screaming about the top benefits of compost tea. So, what is compost tea? Compost tea is a liquid fertilizer otherwise known as liquid gold or black gold.

The basic form of compost tea

In its basic form compost tea is steeping biologically rich and aged compost with water. Most importantly, over the years gardeners have further enhanced this with various additions, including worm castings. Known for their biological activity. And replacing a percentage of the water with other forms of tea. Such as nettle tea or comfrey tea.

This adds further nutrients to the compost tea. As biology are alive they need a food source and for that most people use molasses.

There are two methods for brewing compost tea. Those methods both have scientific research behind them and each has its merits. Furthermore, the two processes of brewing compost tea are aerobic and anaerobic. Let’s talk about the latter first. Anaerobic is compost tea that is as you can see in the above photo.

By brewing the tea and placing a lid on the bucket, you will omit all air and the resulting liquid will turn anaerobic. By far the most used method and the one I use is the aerobic method. This is where you add a mechanical air pump that was designed for the aquatic industry, to pump air into the compost tea.

The Principle Of Compost tea

The whole principle behind compost tea is to increase the amount of biological life within the soil. Because we all know about the soil web life helps plants grow and fend off disease. That’s the benefits of compost tea. I will do another blog on that at a later date. But to increase the quality and yields of our fruits and vegetables we need to increase fertility. This will help us to get a better-looking garden. We need to look after the soil web life. Furthermore, what compost tea does is increase the bacteria and microbes that we would be adding when mulching with compost.

Soil food web

It is important to understand the soil food web. Because of the way we are trying to increase that very nature, by adding compost tea. What does all this have to do with better plants? By introducing a highly beneficial group of bacteria, fungi, protozoa and nematodes we are increasing the amount of good life within the soil.

This, in turn, breaks down within the cycle which provides natural nutrients which can be readily taken up by the plants. Because this is what compost tea is all about, We are literally just giving the microbes everything it needs to reproduce their numbers by the billions. furthermore, this, in turn, will feed your soil. Ever heard of the saying ‘feed your soil not your plants’? This is exactly what is meant behind that saying.

How Long Should You Brew?

How Long should you leave the brew? This really depends on the amount you are brewing and the quantity of molasses you used. However, three or four days should be an ideal amount of time. Once the compost tea is ready it should be used immediately as it doesn’t really store. The microbes start to die without the oxygen and food that is required. It is possible to add additional water, compost and molasses to continue the brewing process.

Compost tea can be used to water your plants. You can not overuse the compost tea so there is no real danger of using too much. Use as much fluid as the plant needs. It can also be used as a drench and this can aid plants to fend of fungal and blight attacks

Benefits of using compost tea

  • Improvement in plant size and quality. Compost teas are jam-packed with nutrients and trace minerals which aid in plant growth and strengthening the plant’s immune system.

Soil Web Life

  • Increases the soil food web life. The larger the community building the structure of the soil the better, This adds fertilisers which are also available to the plants and can change a soils makeup.


  • Is totally organic. Making your own compost tea allows you to control the soil and plant life within your garden. Instead of killing your soil life with chemicals. You are creating a thriving environment which is self-sustaining

Suppresses weeds

  • Helps to suppress disease and pest damage. Compost tea helps to build the plants immune system. Which, in turn, allows the plant to fend off attacks from pests or diseases such as blight.

No Chemicals

  • Breaks gardeners reliance on toxic chemicals. Returning your garden to a more natural balance where mother nature shows you how it’s done.

Warm inside

  • Makes you feel warm inside :). You know you’re doing your little bit to look after the earth. The animals that use your garden, and your family. By providing nutrient-dense organic great tasting food.

Both of these products are available to make this whole process easier for you. If you want to brew your own compost tea, you can just purchase these and start your journey into improving your soil for high-quality plants.

I really hope you will give your garden some help. Increase that soil life and feed the soil by making your very own compost tea. Once you do this you will see the benefits of compost tea in your garden.

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I am Tony O'Neill, A full-time firefighter and long term gardener. I have spent most of my life gardening. From the age of 7 until the present day at 45. My goal is to use my love and knowledge of gardening to support you and to simplify the gardening process so you are more productive

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