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How to Brew Compost Tea

Tea For Plants

A Guide to Brewing Biologically Active Compost and Garden Teas

Best Location for Your Brewer:

  • Place your brewer on a flat and level surface located near a power outlet
  • Provide as stable of an environment as possible such as a shaded location outdoors, basement, barn or garage.
    • Brewing compost and garden teas can be messy at times. A location that can tolerate a few spills is a good idea.

Always Start with Chlorine Free Water:

  • The microbes in compost teas are highly sensitive to anti-microbial agents such as preservatives and chlorine that exist in many municipal water sources.
  • If you have a municipal water source you will want to evaporate as much of the chlorine as possible. This can be achieved by allowing your water to sit in your brewer without a lid overnight or you can aerate your water for 15-30 min prior to use.
    • Fresh, clean rainwater can be a great alternative to the tap.

- High temperatures can kill microbes.

- Low temperatures slow microbial activity.

  • Matching your water temperature to the temperature of the soil or leaf zone where the tea is to be applied is great option. The microbes that are cultivated in your compost or garden teas are more likely to remain active when applied to the soil or a leaf surface that is a similar temperature as your tea.
  • *An aquarium heater can be used to maintain constant temps for more precision brewing and reducing brew times. 

Maintain Constant Temperatures:

  • High temperatures can kill microbes.
  • Low temperatures slow microbial activity.

The microbes that are cultivated in your compost or garden teas stand a higher chance of survival when applied to the soil or a leaf surface that is the same temperature as your tea.  Starting your teas at temperatures as close to the temperature of the soil or leaf zone where the tea is to be applied is your best option.  Place your brewer in a warm shaded spot outdoors or in a basement or garage.
*An aquarium heater can be used to maintain constant temps for more precision brewing and shorter brew times.  Brewing time can be reduced in half when starting with room temperature water.

 Ensure a Quality Extraction:

            In brewing teas we are attempting to transfer the multitudes of beneficial organisms and soluble nutrients into a solution that can be easily applied to plant surfaces and soils.

            In compost teas the compost serves as a starter agent, much like yeast is to bread. Water is the medium and the food sources serve as a catalyst feeding active and dormant organisms present in mature compost. Aerating and agitating the compost in good quality water and providing select food resources will help to promote the growth of the target organisms present in the compost.

Extraction Methods:

I. Compost Extract

            Compost extracts can be made in less than 30 min and can be applied immediately.

  1. Fill your brewer with chlorine free water or aerate municipal water as described above
  2. Place the recommended amount of compost into a 400-micron filter bag

- This will help to keep your brewer more clean and will prevent components from becoming clogged with compost.

  1. Place the compost bag into your bucket or barrel and aerate or gently massage compost bag

            for no less than 1 – min and no more than 30 minutes

II. Aerated Compost Tea

1. Place the recommended amount of compost into a 400-micron filter bag

2. Place the compost bag into your bucket or barrel of chlorine free water and aerate for

            24 hours

3. The compost bag can be removed after 24 hours

            - Do not squeeze or press the filter bag as you may force sediment thru the mesh that                           could clod your air-diffuser and/ or spray nozzles.

4. Now add the recommended food sources

5. Brew your compost tea for the recommended minimum or maximum time and apply

III. Fertilizer Tea For Plants

1. Place the recommended amount of raw ingredients into a 150-micron filter bag

2. Place the bag into a bucket or barrel of chlorine free water and aerate up to 12 hours

3. Remove the bag and apply tea as a soil drench

            - Do not squeeze or press the filter bag as you may force sediment thru the mesh that could clod your air-diffuser and/ or spray nozzles.

 Customize Your Compost Teas for Plant Types, Disease, or Pest

These are general guidelines; recipes may need to be adjusted according to active biology present in your compost.

  • *All-purpose / Balanced Tea (equal Bacteria to Fungi biomass ratios):

This is the most effective tea for all types of plants and soils: Use on most vegetable crops, grasses and pastures, flower and herb gardens, berries, fruit trees or to manage some pest and pathogen outbreaks.

  • Bacterial Tea: Use on brassica family crops or to help manage pests.
  • Fungi/ Humus Tea: Use on deciduous and conifer trees, orchards, vine crops shrubs, acid-loving plants, or to manage pathogen outbreaks. Fungi dominated teas can also be used to enhance the growth of moss.

Brew Times:

  • All-purpose / Balanced Tea (equal Bacteria to Fungi biomass ratios): Brew for24 - 36 hours to encourage a more balanced life within the compost tea.
  • Bacterial Teas: Brew for 12 - 24 hours to encourage bacterial biomass.
  • Fungi/ Humus Teas: brew for36 - 48 to encourage a fungal biomass. After 48 hours compost tea begins to express protozoa dominance, which mainly feed on bacteria.

 Brew times may be reduced by up to half if you are starting with a few quarts of a good quality compost tea. Think of this like a bread starter.

Ingredients and Biological Food Sources


    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.

Bacterial Dominated Compost

  Earthworm Castings/ Vermicompost:

    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)

  Fungal Dominated Composts:

  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.

Making You 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

  Simple Sugars: Molasses, Sorghum, Honey, Maple Syrup, Cane Sugar

    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.

  Kelp: Meal & Soluble Kelp Powders

    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:

    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:

    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.

  Rock meals & Volcanic Rock/ Ash Powders;

    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.

  Alfalfa Meal:

    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.

  Bat Guano:

    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 inoculums

    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

Application Guide for Compost Tea

Apply teas as soon as possible:

  • Compost teas are best if used immediately at the end of a brewing cycle. Compost tea should not be kept for more than 72 hours after removing from active aeration.
  • Compost teas can be refrigerated for up to 30 days. Garden teas such as plant extracts or home brewed fertilizers may keep for longer periods in refrigeration. Allow teas to return to room temperature and re-activate teas with aeration for 1 or more hours.
  • Always test the smell of your stored teas. If they smell foul most likely oxygen levels have been depleted and the compost tea is void of oxygen or anaerobic. It is best not to apply anaerobic foul smelling teas, instead apply to your compost heap(s) lawns or away from precious plants.    

 When to apply compost teas:

  • For best results apply monthly or at more regular intervals as needed.
  • In late winter or early spring: Spray all trees, shrubs, and perennials with fungal dominated compost teas brewed for 36 - 48 hours at least once at the following times:

            - Before the formation of flower / leaf buds.

            - Apply when flower / leaf buds break but have not opened.

  • Apply a fungal dominated compost tea as a soil drench around trees, shrubs, and perennials monthly or more frequently.
  • During the growing season: Apply at the first sign of any disease or insect infestation. Fantastic results have been reported with bi-weekly applications as a preventative measure.
    • Treat disease such as blight and leaf spot with fungal or balanced teas.
    • Treat insect infestations with bacterial dominated compost teas.

    Severe insect infestations are a sign of a nutritionally deficient plant. Heavy infestations may need to be treated with an organic pesticide to quickly kill the majority of the infestation. This action should be followed the next day with a bacterial compost tea to ensure the proper biology is present and to help strengthen the sick plant. This will act as a pro-biotic for your plants and soils. Repeat this process weekly or as needed.

How much tea do I apply?

  • For best results use teas at full-strength. A full-strength tea will possess the maximum active biological diversity or nutrition content and be most effective. Compost and garden teas can be diluted at any ratio up to 10:1. A 10:1 ratio is easily achieved by using a hose siphon to apply filtered teas.)
    • You can never apply too much compost tea.
    • Repeated applications of compost teas will only help to increase the diversity and populations of beneficial microbes.
    • Compost teas can be applied as a soil drench or root dip when transplanting. Compost and garden teas can also be sprayed directly onto a leaf surfaces or diluted with a hose siphon for easy application.
      • As a root drench apply 5-10 gallons (full strength) or diluted up to 15:1 per 1/4 acre.
      • As a foliar spray apply 5-10 gallons per acre.
      • As a field spray apply 5 gallon per 2 acres.

How To Apply Compost Teas:

It is best to apply compost teas when plants and soil are moist. Early morning and/ or near dusk, when dew conditions are present, help to ensure that beneficial organisms cultivated in compost teas make good contact with leaf and soil surfaces and remain active.

Soil Drench (soil and root inoculants)

  • It is best to apply when the soil is moist early in the morning or late in the evening.
  • Apply at regular watering intervals for outstanding results.
  • Apply from the base of plant as far out as the plants drip line or root mass.
  • Use plastic watering vessels as bacteria can eat-away at the zinc in metal.

Leaf/ Foliar Applications

  • Use a clean hand pump or pressurized sprayer. It should be noted that not all sprayers are built alike. Some allow for larger particles to pass through the spray nozzle(s) with ease. Diaphragm sprayers work great for this type of application. We have experienced good results with the Solo brand backpack sprayers. If using a Gilmore or equivalent brand 2-gallon type of handheld sprayers we suggest upgrading the sprayer wand with a more durable and versatile sprayer wand.
  • Do not exceed 70 psi (slow dispersion is better). Most hand pump and diaphragm sprayers will not exceed 70 psi.
    • Spray pattern should be wide and gentle with no hard splattering
    • Teas should cover 70% of the leaf surface for maximum effectiveness and remain moist for 15 minutes or longer.
      • Avoid spraying open flowers and fuzzy-leafed plants, like African violets.
      • In dry conditions, spray teas early in the morning or in the evening to allow the organisms in the tea to remain moist and active after application.

Best time of day to apply compost and garden teas.

  • Ultraviolet rays from the Sun can kill microbes so it is best to apply teas before 10:00am or after 6:00pm regardless of cloud cover and the time of year.
    • Avoid spraying teas in heavy rain or prior to a rainfall.
    • Moist and misty mornings or after rain is an excellent time to apply compost teas.

Apply teas as soon as possible:

  • Compost teas are alive and as oxygen levels in the tea decreases so will the populations of the active aerobic organisms you have cultivated. Teas are best if used immediately after removal from the highly aerobic environment of your Garden Tea Brewer. It is best to use all your tea within 72 hours of removal from your Garden Tea Brewer.
    • If your tea sits too long and smells foul then discard in a compost heap.
    • You can never apply too much compost tea.
    • Undiluted teas work great; however, teas can be diluted at any ratio up to 16:1. This 16:1 ratio is easily achieved by using a hose siphon and a watering wand.
    • Repeated applications of compost teas will only help to increase the diversity and populations of beneficial microbes.
    • Compost teas can be applied as a soil drench or root dip when transplanting. Compost and garden teas can also be sprayed directly onto a leaf surfaces or diluted with a hose siphon for easy application.


Clean your brewer, watering vessels, and/ or spray applicators immediately after each batch of tea or application: (remove all tea and bio-slime residue as soon as possible)

  • Thoroughly clean brewer bucket, air-hose, air-diffuser and spray applicator after each batch of tea.
  • Use dish soap and a scrub brush to clean all residue known as bio-slime from all of your components before storing.
  • The air-diffuser included with our Garden Tea Brewer can be safely cleaned in the dishwasher.
  • “No Rinse Cleansers”, such as One-Step, used to sanitize bottles and equipment for the home brewing of beer wine making works well to sanitize your equipment.
  • Hydrogen Peroxide can also be used to sanitize your equipment. Hydrogen Peroxide will kill many microbes and using it with dish soap and warm water works as a thorough cleanser.
    • Baking soda can be used as an abrasive cleanser.