What is Compost Tea and How Do You Make It?

Compost tea is an organic liquid fertilizer made by steeping finished compost in water. The steeping process extracts beneficial microbes, nutrients, and humic acids from the compost into the water, creating a concentrated liquid extract. This resulting “tea” can then be applied directly to plants and soil as a nutrient-rich foliar spray and soil drench.

Compost tea provides plants with a boost of organic matter, microorganisms, and soluble nutrients. It’s an excellent way to build healthy soil biology and enhance plant growth organically. When used regularly, compost tea can improve plant health and vigor while reducing the need for synthetic fertilizers and pesticides.

Read on to learn what compost tea is, why it’s beneficial for plants and soil, and a simple process for brewing your compost tea at home with easy-to-find ingredients.

What Is Compost Tea Exactly?

Compost tea is made by steeping high-quality, finished compost in water for 24-48 hours. An aquarium pump bubbles oxygen through the mixture while it brews. This oxygenated environment helps extract and multiply the microorganisms living in the compost.

The finished compost tea is filled with beneficial bacteria, fungi, protozoa, and nematodes. It also contains soluble nutrients like nitrogen, phosphorus, and potassium that leach out from the compost. The compost acts as a natural growth medium for the soil microbes to rapidly reproduce in the aqueous solution.

Good compost contains a diversity of microorganisms that are beneficial to plant and soil health. By extracting them into a liquid fertilizer, compost tea makes these living microbes easily available for uptake by plants.

The microbes colonize plant root systems and leaves, protecting them from disease while enhancing their ability to absorb nutrients. The microbes also benefit the soil food web when compost tea is poured onto the ground. They condition the soil, decompose organic matter, and release bound nutrients.

Compost tea is a concentrate teeming with life that delivers a boost of biodiversity wherever it is applied. It supports robust root growth, disease suppression, and nutrient cycling to help plants thrive naturally.

Compost Tea Provides a Package of Benefits for Plants and Soil

There are many benefits of using compost tea as an organic foliar spray and soil amendment:

  • Delivers a concentrated dose of beneficial microbes – bacteria, fungi, protozoa – that colonize plant roots and leaves. These microbes protect against foliar and soil-borne diseases, aid nutrient absorption, and improve soil biology.
  • Provides soluble nutrients from the compost, like nitrogen, phosphorus, potassium, and trace minerals. The nutrients are in a plant-available, water-soluble form that is immediately accessible for plant uptake and growth.
  • Contains humic acids that stimulate root and shoot growth as natural plant hormones. Humic acids also help retain moisture and nutrients in soil.
  • Increases soil organic matter as the microbes decompose and incorporate the compost particles, building soil structure and fertility.
  • Promotes rapid nutrient cycling as the compost tea microbes mineralize and convert nutrients into plant-available forms.
  • Enhances soil ecology by adding billions of beneficial microorganisms per gallon that balance the soil food web.
  • Acts as a foliar fertilizer when sprayed on leaves, providing nutrients directly to plants.
  • Improves plant resilience and vigor. The compost tea supports disease suppression, nutrient absorption, and growth hormone production to grow stronger, healthier plants.

How to Make Compost Tea at Home

Making compost tea is a relatively simple process that takes a couple days from start to finish. Follow these steps for brewing a balanced, microbe-rich compost tea:

Supplies Needed

  • 5 gallon bucket
  • Compost – Use 1 cup per gallon of water. Finished compost works best.
  • Compost tea additives (optional) – molasses, seaweed/kelp, fish emulsion
  • Compost tea bag – a porous bag or pantyhose to contain compost
  • Water – non-chlorinated
  • Aquarium air pump
  • Air stone

Brewing the Tea

  1. Fill a 5 gallon bucket about 3/4 full with non-chlorinated water. Well water or stored rainwater works best. Leave space at the top for the compost and additives.
  2. Place 1 cup of finished compost per gallon of water in a compost tea bag or pantyhose. Tie the bag to a stick placed over the bucket to keep the compost suspended in the water.
  3. Add any compost tea additives. A few tablespoons per gallon of molasses, seaweed extract, or fish emulsion will feed the microbes and provide extra nutrients.
  4. Place an aquarium air pump and air stone in the bucket. The air stone bubbles oxygen through the water to maintain aerobic conditions.
  5. Let the compost tea brew for 24-48 hours. The microbe population will grow and extract nutrients over this time.
  6. When finished, turn off the pump and remove the compost bag. Pour the finished compost tea into a watering can to apply.
  7. Use the compost tea within a few hours. The microbes will start to die off without oxygen, so apply as soon as possible.
  8. Clean equipment well after use. Rinse the bucket, tubing, air stone with clean water.

Follow this simple process using local, organic compost and you’ll have a living compost tea bursting with microbes and nutrients to boost your garden.

Tips for Making High Quality Compost Tea

  • Use mature, finished compost rather than fresh compost for the best microbial extraction.
  • Add compost at a ratio of 1 cup per 1 gallon of water. Higher concentrations can be too strong.
  • Brew for 24-48 hours. Less time won’t fully extract the microbes and nutrients.
  • Keep the solution aerobic by using an air pump for the duration of brewing.
  • Use non-chlorinated water if possible. Chlorine will kill beneficial microbes.
  • Store tea in the shade and use within 6 hours after brewing for maximum effect.
  • Clean equipment thoroughly after each use to prevent harmful bacterial growth.

When and How to Apply Compost Tea

Compost tea provides benefits when applied either as a foliar spray or a soil drench:

As a Foliar Spray

  • First, filter finished tea through a fine mesh strainer to remove large particles.
  • Pour tea into a sprayer bottle. Apply to leaves in the early morning or evening to avoid hot sun which can burn leaves.
  • Mist both sides of leaves and shoots with a light coating. Avoid excessive runoff.
  • Repeat applications every 1-2 weeks during the growing season to build plant defenses.

As a Soil Drench

  • Use finished tea within a few hours before microbe viability declines.
  • Pour tea directly around the base of plants, wetting the root zone area. Also apply between rows in garden beds.
  • Water deeply after applying to move the microbes into the soil profile.
  • Reapply every 2-4 weeks to maintain enhanced soil biology.

General Tips

  • Test on a few plants first to ensure the tea concentration is not too strong.
  • Apply in the morning or evening to avoid hot sun that can burn wet foliage.
  • Alternate between foliar feeding and soil applications to maximize benefits.
  • Use compost tea as a supplement to compost top-dressing for a regular nutrition and microbial boost.

Choosing Compost and Additives for Optimal Tea

The ingredients you use will greatly impact the microbial life and nutrient content of your finished compost tea. Follow these guidelines for selecting compost tea materials:


  • Use well-finished thermophilic compost that has gone through the high heat phase. Avoid immature compost.
  • Seek compost made from a diverse mix of feedstocks like manure, food scraps, yard debris, and crop residues.
  • Source local, organic compost produced through aerobic decomposition without chemicals.
  • Allow compost to fully cure for 3-6 months after the pile has finished, letting it stabilize.

Compost Tea Additives

  • Molasses – provides food for beneficial microbes to grow and multiply. Use 1-3 tbsp per gallon.
  • Kelp or seaweed powder/meal – contains over 60 trace minerals, plant hormones, amino acids, cytokinins, etc. that aid growth. Add 1-2 tbsp per gallon.
  • Fish emulsion – supplies nitrogen, phosphorus, proteins, and oils to feed microbes. Use a few tablespoons per gallon.
  • Rock dust – adds a wide spectrum of micronutrients. Sprinkle in 1-2 tbsp per gallon.
  • Humic/fulvic acid – aids nutrient uptake. Add per product instructions.

Using quality compost and additives maximizes the diversity and concentration of microbes extracted into the tea along with a broad spectrum of plant nutrients.

Best Plants to Fertilize with Compost Tea

Compost tea provides benefits to all garden and landscape plants. Some particular plants that especially thrive with regular compost tea applications:

Vegetables and Fruits

  • Tomatoes – enhances disease resistance against blights. Produces thicker stems and foliage.
  • Peppers – grows stronger plants less prone to wilting. Aids fruiting and ripening.
  • Lettuce and greens – grow faster with fewer bitter leaves. Improves shelf life.
  • Broccoli, cabbage, cauliflower – makes plants less susceptible to fungal and bacterial rots.
  • Strawberries – increases berry size and sweetness. Extends harvest season.
  • Citrus trees – helps suppress soil diseases like root rot.

Flowers and Herbs

  • Roses – stimulates blooming and enhances color. Wards off common rose diseases.
  • Annuals and perennials – flowers more prolifically with bigger, brighter blooms.
  • Cannabis – produces higher flower yields with more trichomes (resin glands).
  • Basil, oregano, mint – encourages healthy oil production improving flavor.

Trees, Shrubs and Lawns

  • New transplants – reduces transplant shock and stimulates root growth.
  • Conifers – defends against root diseases like phytophthora. Improves needle color.
  • Fruit trees – increases fruit set and quality. Boosts branch growth.
  • Lawns – reduces fertilizer needs and weed/pest pressure. Enhances soil.

Other Benefits

  • Houseplants – nourishes plants and keeps potting mix biologically active.
  • Seed starts – promotes vigorous seedling growth and wards off damping off disease.
  • Tired soils – restores biology to damaged or depleted soils. Also great for container plants.

Regular foliar sprays and soil applications of compost tea provide a nourishing boost of organic matter, microbes, and nutrients. Make your own compost tea to grow thriving plants and build living soil!