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Skill Level: Beginner

You've probably heard of compost, which helps add valuable organic matter to soil. But making and using compost tea may be a less familiar concept. Think of this liquid as a "quick-release" form of compost, packed with garden-boosting properties. Buying ready-made compost tea can be expensive, and because it's most effective when freshly brewed, packaged products may not be as beneficial. The best compost tea is the batch you make yourself, which is easy to do with a few simple ingredients and supplies, plus a little bit of time.

What is compost tea?

Compost tea is a simple mixture created by soaking organic compost in water. Although the recipes and techniques can differ, a well-made compost tea will be rich in the nutrients that plants need to grow. What’s more, compost tea is full of beneficial microorganisms, such as fungi, bacteria, and nematodes, which support plant health and can improve soil structure. Once applied, this powerhouse product can help your plants grow faster, naturally resist pests and diseases, and increase harvest yields. With the help of compost tea, you can reduce or eliminate the use of pesticides and fertilizers in your garden.

How to Make Compost Tea

Compost teas can be made with or without aeration—it’s up to you. Aerated compost teas use a bubbler during the brewing process to boost oxygen levels and “compost food” to increase the activity of beneficial microorganisms. Aerated compost teas can be brewed faster; however, they are not as stable and need to be used immediately. Non-aerated compost teas still should be used as soon as possible, but they are more stable and require fewer ingredients. Use the following compost tea recipes to get started on your next batch.

What You'll Need

Materials

5-gallon bucket
Non-chlorinated water
2 to 4 cups of compost
½ to 1 cup of compost food (equal parts unsulphured molasses and fish and kelp hydrolysate mixed with 1 tablespoon of humic acid)
Nylon stocking
Aquarium air pump
Stirring utensil
Cheesecloth

Instructions

Aerated Compost Tea

Add Water to Bucket

The day before you want to make your compost tea, fill your bucket with water to a few inches below the rim. Allow the bucket of water to rest overnight. This will reduce chlorine in tap water, which could otherwise damage the microorganisms in your compost tea.
Fill Stocking

The following day, add compost to the nylon stocking. Knot the open end of the stocking to keep your compost secure.
Add Stocking, Bubbler, and Compost Food to Bucket

Add the stocking of compost and air bubbler to your bucket and turn the bubbler on. A properly calibrated air bubbler should agitate the water and make it churn. Pour in the compost food mixture.
Let Brew

Allow your compost tea mixture to brew for 24 to 36 hours. At the end of this time, you should be left with an earthy-smelling compost tea that may be a bit frothy.

Warning

If your tea smells bad, the compost tea was probably not aerated enough and the mixture has gone off. Dispose of the bad brew and try again.

Non-aerated Compost Tea

Fill Bucket

The day before you want to make your compost tea, fill your bucket with water to a few inches below the rim. Allow the bucket of water to rest overnight. This will reduce chlorine in tap water, which could otherwise damage the microorganisms in your compost tea.
Add Compost

The following day, add compost to your bucket of water and stir it well for about 2 minutes. Then, for the next 7 to 10 days, stir your compost tea once or twice a day.
Strain Out Compost Particles

Optional: If you want to use your compost tea with a garden sprayer, strain out the large particles with cheesecloth or another strainer to avoid clogging up your sprayer.

Tips for Making Compost Tea

Certain ingredients and conditions can impact how your compost tea recipe turns out. These tips will help ensure your success:

Compost tea is only as good as the compost that is used to make it. So if you want a high-nitrogen tea, you’ll need to use compost created with lots of nitrogen-rich materials.
While worm castings can be used to make compost tea, avoid using fresh animal manure with this process as it can contain harmful bacteria such as E. coli.
Use dechlorinated water to brew your compost tea because chlorine may kill the beneficial microorganisms in your compost.
If you’re making compost tea outdoors, make sure air temperatures stay between 55 and 85°F. Extreme temperatures may slow or even halt microorganism activity and reduce the effectiveness of your compost tea.

How to Use Compost Tea

Compost tea can be poured directly on soil, known as a soil drench, or applied as a foliar spray that the plant will absorb through its leaves. Soil drenches can enhance overall plant health and pest resistance, boost plant growth, and improve your garden soil structure, nutrient content, and water retention capabilities. Foliar sprays can also help plants better resist pests and pathogens, and are a good way to ward off common diseases like powdery mildew and leaf spot. Compost tea can be used on both indoor and outdoor plants.

Using Compost Tea as a Soil Drench

Undiluted compost tea may burn plant roots, especially if it has a high nitrogen content. To avoid this, dilute your brew before use. How much you want to dilute your tea is up to you, but ratios between 1:4 (1 part compost tea to 4 parts water) and 1:10 are common. After diluting your compost tea, gently pour the liquid around plant roots. For best results, apply compost tea at a rate of 1 gallon of tea per 100 square feet of gardening space.

Editor's Tip

Adding compost tea to your houseplants and garden soil will reduce the amount of fertilizer you need to add to your plants.

Using Compost Tea as a Foliar Spray

Compost teas can be sprayed on plant leaves to prevent common plant pathogens. To do so, add your compost tea to a garden sprayer and dilute it with water to 1:4 to 1:10 strength. Apply your compost tea only in the morning, as bright sunshine may kill the beneficial microorganisms in the tea.