How to Make Compost Tea—and Use It to Encourage Plant Growth and Prevent Pests

TABLE OF CONTENTS

1. On This Page

   • What Is Compost Tea?

   • Benefits

   • How to Make Compost

   • Compost Tea Recipe

   • How to Use

   • Brewing Mistakes

The most rewarding part of gardening is seeing your plants flourish. Whether that means healthy blooms on your perennials or robust vegetation on your tomato plants, witnessing your labor pay off is a goal many gardeners strive for. But if your flowers are looking a little lackluster or if your crops just aren't growing, you may be looking for a solution. Enter: compost tea.

The tea-colored liquid is filled with micronutrients that can promote plant growth, increase yield, and keep pests at bay. While it may seem like a complex process with many moving parts, making compost tea at home is actually quite easy—all you need is the right compost tea recipe and water, compost, and a bucket.

Related: Stash Your Food Scraps in These Kitchen Countertop Compost Bins

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What Is Compost Tea?

Compost tea, also known as liquid extract, is the process of extracting liquid from solid compost material. "You're taking finished compost and you're steeping it in clean water, which extracts the nutrients and microorganisms that are in the compost," says Rhonda Sherman, director of the Compost Learning Lab at North Carolina State University. The microorganisms in the compost are given an environment in which they're able to flourish and multiply, and can then go on to be used to benefit your plants.

Benefits of Compost Tea

There are many benefits of administering compost tea to your plants. "It enhances plant growth and it increases the yield of that plant," says Sherman. "If you're growing a vegetable, fruit, or a flowering ornamental, for example, there's going to be more of those fruits, vegetables, and flowers if you're using this tea." In addition to enhancing plant growth and yield, compost tea can also encourage the roots to grow bigger and stronger.

Another important benefit of compost tea is that it's a natural way to keep pests at bay. Some of the microorganisms extracted from the compost release by-products that prevent diseases and in turn keep pests and insects from being attracted to your plants.

How to Make Compost

In order to make compost tea that actually works, you need quality compost. Your compost should provide an environment where microorganisms can thrive. "Microorganisms are living beings that have similar needs that you and I have," says Sherman. "They need water, air, shelter, and food, so that's what you need to supply to them."

Typically, quality compost is made by combining a mixture of food scraps and tree leaves either outside or in a compost bin. A compost bin is the easiest method as it keeps the compost contained and prevents the odor from escaping. There are many ways to make compost, but Sherman recommends the following method.

1. Fill a compost bin 2/3 of the way full with dead tree leaves, moistening the leaves as you add them to the bin.

2. Pull back some of the leaves and make a hole in the center.

3. Add your food scraps to the hole.

4. Cover the food scraps with the excess leaves you pulled back.

5. Let the compost sit for about six to 12 months.

Over time, the microorganisms will break down the materials and turn it into finished compost, which smells and looks like soil. Most compost bins have a door where you'll be able to see the finished compost, which can then be pulled out with a shovel and used for the tea.

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Compost Tea Recipe

There are two methods for making compost tea: aerated and non-aerated.

Non-Aerated Method

"One of the first methods that was ever created was non-aerated," says Rick Carr, farm director at the Rodale Institute. "And this is the simplest way to do it if you're just a homeowner or backyard gardener." To make non-aerated compost tea all you need is a few ingredients: compost, clean tap water, a mesh bag, and a bucket.

Ingredients

• 1 gallon non-chlorinated water

• 1 1/2 cups finished compost

• 5 gallon bucket

• Mesh bag

Directions 

1. Put finished compost into a mesh bag.

2. Put the mesh bag into a bucket.

3. Fill the bucket with non-chlorinated water.

4. Place the bucket in a cool, dark place.

5. Stir the mixture every day for one week.

Aerated Method

An alternative (and quicker) way to make compost tea is to aerate it. Aerated compost tea is made following the same steps outlined above, with the only difference being that you should place an aquarium bubbler into the bucket along with the water and compost.

Pros

The bubbler gives you the capacity to produce a higher microbial community. "That heightened level of dissolved oxygen in the solution will permit an environment for microbes to flourish, more so than non-aerated," says Carr. Additionally, aerated tea is much quicker to make than non-aerated. Generally, it's ready about 48 hours after the start of brewing.

Cons

Besides the fact that it requires more equipment than non-aerated tea, there are downsides to taking this approach. As soon as you discontinue the microorganisms' oxygen source, they'll immediately consume the oxygen, which may result in a microbial community crash.

Because of this, you'll need to use the aerated tea almost immediately after turning off the bubbler. Even then, you may not see a true benefit from a higher microbial count. "There's nothing to say that a higher amount of microbes is going to lead to a better garden," says Carr.

How to Apply Compost Tea

The tea should be administered to your plants about once a week. It can be applied two ways: poured into the soil around the base of a plant or sprayed onto the leaves as a foliar. When sprayed onto the leaves (which should be done using a backpack sprayer) the tea helps to suppress diseases and pests. On the other hand, pouring it onto the soil with a watering can sends the nutrients right to the roots, which will help increase plant growth.

Compost Tea Brewing Mistakes

As is the case with many gardening projects, there's bound to be some bumps in the road when brewing compost tea. Make the process easier on you and your plants by avoiding some of these common pitfalls.

Using Chlorinated Water

While it's perfectly fine to use tap water on your plants, you should ensure it's non-chlorinated. "Tap water that's coming from a city is going to have chlorine in it," says Sherman. "You would fill that bucket with water and then leave the bucket aside for 24 to 48 hours, so the chlorine will evaporate from the water."

Using Dirty Equipment

In addition to clean tap water, you should ensure the bucket you're using is clean, too. "There's all types of microorganisms and there's bad ones that make you sick," says Sherman. Not cleaning out your equipment before brewing tea can mean you're leaving behind those dangerous microorganisms.

Using Sugar

One of the biggest mistakes people make when brewing compost tea is adding sugar to the compost-water mixture. "Do not put molasses or any type of sugar in the tea brewer," says Sherman. "A lot of people will recommend it because it will increase the number of microorganisms, but if you have pathogenic microorganisms (like E. coli or salmonella) then you've just increased their populations, too."