Making Compost Tea: What Is It and How Do You Use It?

These days more and more gardeners are looking for natural alternatives to commercial fertilizers and soil amendments. Many have found that compost tea is an excellent option for plant nourishment and soil replenishment.

  • What is compost tea?
  • What does it do?
  • How do you use it?
  • What about worm compost tea?

In this article, we will explore these questions and help you learn about the many benefits and uses of compost tea. Read on to learn more.

Why Is Organic Compost Better Than Commercial Fertilizer?

Compost is produced through the decomposition of animal and plant materials. Most gardeners are familiar with the benefits of composts for soil and plants of all kinds.

Both indoor and outdoor gardeners often produce natural, organic compost by layering and mixing organic materials in a compost pile or bin in a way that speeds their decay to create a nutrient-rich product that can be used as a seed starting mix, soil amendment or fertilizer.

Healthy soil contains a multitude of beneficial nematodes, protozoa, fungi, and bacteria.

Adding compost to your soil provides the beneficial microbes living in the soil with food. These microbes process compost and turn it into nutrients for your plants. High-quality organic compost helps colonies of beneficial organisms flourish.

Keeping a compost heap or bin takes a little work, but the result is much better than any commercial fertilizer you could purchase. Using chemical fertilizers starves the beneficial flora and fauna in the soil.

Furthermore, artificial nutrients do not improve soil structure at all, but organic matter improves both the porosity and the aeration of the soil.

When you add organic matter to your soil on a regular basis, it also helps increase the population of mycorrhizae surrounding the roots of your plants. This beneficial fungus helps the roots of the plants make better use of nutrients and moisture.

Isn’t compost enough?

Even though homemade, organic compost provides a wealth of benefits for your plants and soil, compost tea takes it a step further.

Soil biologists have found that “brewing” high-quality compost in aerated water with molasses and other nourishment for several days produces a liquid “fertilizer” that is just brimming with healthy beneficial microbes.

More on Using Molasses as Fertilizer

Put simply, the difference between organic compost and compost tea is like the difference between healthy foods and food-based vitamins.

Compost provides everyday nutrients on an ongoing basis. Compost tea provides a boost of nourishment and immune boosting properties.

The concentrated beneficial microbes in the tea work to fight off and consume detrimental microbes. Just as your white blood cells eat bacteria and viruses that might make you sick, beneficial microbes prey on detrimental ones and can eliminate large amounts of them. This reduces your plants’ risk of pest infestation and/or disease.

Related Reading: Uses For Old Tea Bags In The Garden 

How Do You Use Compost Tea?

Using homemade compost tea is a smart and thrifty way to feed your plants, and it helps the environment as well. When you use this natural product, you reduce the number of chemicals required to care for your garden.

Use this supplement just as you would a liquid fertilizer or a foliar fertilizer. A more concentrated solution can be used as a soil drench to water your plants occasionally. A dilute solution makes a good foliar spray.

Reducing the number of chemicals you use in your home and garden positively impacts air, soil, and water. For many decades gardeners have used large amounts of chemical fertilizers and fungicides.

These products kill off microbial life in the soil and pollute groundwater through saturation and runoff.

By replacing commercial products with your own homemade fertilizers and soil amendments, you are doing your part to restore a thriving population of microbes to the soil and keep water clean for everyone.

5 Benefits of Compost Tea

  • Beneficial microbe populations improve in both numbers and biodiversity.
  • Regular use of compost and compost tea builds up soil nutrients and improves soil’s water retention capabilities.
  • Using natural nutrients and amendments reduces the number of contaminants leached from soil into the groundwater.
  • Use of natural products reduces the accumulation of salts in the soil.
  • Improvement in microbial diversity improves the pH buffering ability in the soil.


How Do You Make Compost Tea?

The old-fashioned way to make compost tea is to take a shovel full of finished compost and put it in a bucket, then fill the bucket with water and just let it sit for two or three days.

When the time is up, strain the tea and use it to water your plants or use it as a foliar spray. This weak tea is known as compost watery extract (CWE). It is a good source of nutrients for plants.

Some older gardening books suggest using fresh manure instead of compost, but this practice is discouraged today. Fresh manure tea is more likely to harbor disease-causing organisms such as E. coli.

It is important to note that this is not true of manure-based, finished compost.

Some gardeners feel that compost tea made with finished, manure-based compost has more powerful and long-lasting disease suppressing abilities than plant-based compost; however, there is no solid evidence of this assertion.

Aeration Improves the Brewing Process

Since the early days of compost tea brewing, the process has been updated to include aeration usually with an air pump. The reason for this is that aerated water encourages the growth of beneficial organisms that help plants fight off diseases.

The liquid produced using compost and aerated water is called actively aerated compost tea (AACT).

Making AACT differs from making CWE because you must add aeration, and it is recommended that you add one or more food sources to further encourage the growth of beneficial organisms. Good food sources can be:

  • Unsulfured molasses
  • Cane syrup
  • Fruit juice

Of these, unsulfured molasses is the favorite because it discourages the growth of undesirable organisms. Fruit juice is the least desirable because it can encourage the growth of E. coli or salmonella.

Other substances that are often added to brewing AACT include:

  • Fish hydrolysate
  • Phosphate rock
  • Orange pulp
  • Fulvic acid
  • Humic acid
  • Kelp

When making AACT, remember you want to create a solution rich in beneficial microorganisms. Successfully brewed AACT contains as many as four-billion beneficial bacteria per teaspoonful.

How Long Does It Take To Make AACT?

This rich supplement should not be brewed for more than three days because allowing it to develop for too long can cause loss of oxygen in the solution. When this happens, undesirable microbes may be able to overpower the beneficial microbes.

Luckily, it is easy to tell if this has happened because the solution will smell terrible if it has been co-opted by bad influences.

How Do You Set Up A Compost Tea Project?

If you are not big on do-it-yourself projects, you can buy an AACT kit at your local garden center or online. These range in size from small, five-gallon setups to large enough for commercial use. You can also make your own actively aerated compost tea setup with a simple five-gallon bucket and an aquarium pump, air line and an aeration stone.

How To Make Compost Tea – Organic Fertilizer For Your Plants

Set your bucket up in an out-of-the-way place that gets good ambient air circulation and indirect light. Fill the bucket with tap water, leaving enough room to add finished compost.

Allow the water to sit (with the aeration system running) for a couple of days. This will allow chlorine and other chemicals to dissipate. This is important because chlorine and disinfecting chemicals will kill off beneficial microorganisms.

After a couple of days pass, add four cups of high-quality, finished compost (along with any nutrients you wish to add). There are a couple of ways to do this.

You can pour the compost into the water loose, or you can put it into a cheesecloth sack or a pantyhose leg (like a giant tea-bag). Allow the concoction to steep for two or three days.

Check on it daily and stir it a bit and move the bubbler around. This will help facilitate brewing. When your mixture is ready, strain it (or remove the compost sack) and use the clear liquid full strength to water and feed your plants. Alternately, mix it 50/50 with dechlorinated water to use as a foliar spray.

Good Compost Makes Good Tea

Remember, the quality of your AACT is dependent upon the quality of your finished compost. If you make your own compost, you can be sure of what’s included. If you are purchasing finished compost from your local garden center, the contents may be a bit questionable.

If you are in a hurry or simply don’t want to make your own AACT, you may be able to find it ready-made at your local garden center. If you go this route, look for a product made fresh, on-site. Commercially produced AACT would need preservatives to keep it from spoiling or fermenting. Naturally, this would defeat the purpose of the product. [source]

Can You Make Compost Tea With Worm Composting?

Worm composting (vermicomposting) is a great way for indoor gardeners and those with limited space to recycle kitchen scraps and create rich organic compost and compost tea.

When you keep a worm bin, you can feed your worms fruit and veggie scraps which they process and turn into worm castings. This rich compost is wonderful for growing houseplants, container plants, and garden plants.

Will Worms Eat Anything?

Worms can eat any organic material, but when your goal is to produce a rich, nourishing compost, it pays to pick and choose what you feed your worms.

Raw fruit and veggie scraps are best because worms can break them down quickly and easily and they don’t tend to smell or attract undesirable pests.

Dairy products, meat, oil and cooked foods are more challenging for worms, and they spoil and cause odor problems in the area surrounding the worm bin.

Worms prefer less acidic foods, so you should not put citrus fruit rinds in your worm bin.

Even if the worms did like them, the resulting soil would be too acidic, and the rinds tend to attract fruit flies. Smelly veggies such as broccoli but the stems are tasty and onions should also be left out of the bin as they will cause odor problems.

How Do You Set Up A Worm Farm?

There are lots of commercially produced worm bins available at garden centers or online, but it is very easy to set up your own worm farm.

You can use a number of different sorts of boxes. Be sure to rinse any container you use thoroughly and allow it to air before setting it up for worms and introducing them.

When setting up your worm bin, just keep in mind the basic requirements to keep worms happy. Ideally, you want to set up an environment that provides:

  • Warmth (50°-70° degrees Fahrenheit)
  • Darkness
  • Moisture
  • Food
  • Air

It’s best to keep your worm bin indoors in a temperature controlled setting. Many people keep the worm bin in the corner of the kitchen or under the kitchen sink. A heated basement is also a good location for a worm bin.

Plastic Totes Are Ideal

The easiest and most readily available container to use as a worm bin is a plastic tote with a lid. You’ll need to drill holes in the top for air and in the bottom for drainage, and you’ll need a second tote or shallow bin to place under the worm bin to catch the drainage, which is your worm compost tea!

Once you have prepared your bin, add some bedding. It’s good to put a layer of torn newspaper and cardboard on the bottom, followed by a layer of leaves. Add some veggie scraps and cover them with another layer of leaves or newspaper.

You’ll want to sprinkle a bit of sand or coffee grounds over the contents of the compost bin from time to time as worms need grit to be able to “chew” their food.

READ: More on the details of Coffee Grounds on Plants

Once per week or so pour some water over the contents of the bin to keep the compost just slightly damp. When you pick up a handful of it, it should feel like a damp sponge.

Where Do You Get The Worms?

Don’t use earthworms from your garden because they will just die. Look online or at your local garden center for red worms (aka red wigglers). They are especially suited to worm composting.

If you cannot find them locally, don’t be afraid to order them by mail. They are inexpensive and travel well. Just be sure to have their habitat set up for them so that you can get them situated as soon as they arrive.

How Big Should Your Worm Bin Be?

Red worms and red wigglers like to live near the surface of their substrate, so a large, shallow bin is preferable. It should be at least 24″ X 18″ X 8″. Of course, you can vary this depending on the number of food scraps your kitchen generates and the amount of space you have for worm farming.

How Do You Collect Worm Compost Tea?

When you set up your worm bin, first put your drainage bin in place. Put a couple of bricks, old flowerpots or 2″ or 3″ lengths of PVC pipe (on end) in the drainage bin to support the worm bin. Set the worm bin on top of these supports.

The water poured into the worm bin to keep the bedding moist, along with the moisture generated by the worms, will drip into the drainage bin. Check this periodically and pour off the liquid every week or two. This liquid is worm compost tea. Dilute it 50/50 with dechlorinated water and use it to water or spray your plants.

If your worm bin does not provide enough worm compost tea on an ongoing basis, you can make more by using finished worm compost and following the directions provided above for AACT.

Can The Worms Stay In The Bin Forever?

Sooner or later, you will have a worm population explosion, so you’ll need to gather your compost and relocate some worms periodically. Generally speaking, every 3-6 months you should remove the finished compost from the bin.

There are a couple of ways to do this. You could dump the whole thing out onto a tarp and separate the compost into several mounds.

Leave it in place with a light on overhead for about 15 minutes. The worms will migrate to the bottom of the mounds, so you will be able to collect the finished compost from the top of the mounds relatively worm-free.

Alternately, you can stop adding food scraps to the bin for a couple of weeks. During this time, the volume of compost in the bin will drop dramatically. When this happens, shift the finished compost over to one side of the bin and set up the empty side with fresh newspaper, leaves, veggie scraps and sand.

Put a cover on the “new” side of the bin and leave the “old” side exposed to air and light. The worms will naturally migrate to the new, moist food source and away from the light and air.

Continue adding fresh food scraps to the “new” side for two or three weeks. At the end of this time, you should be able to remove the older, finished compost pretty easily without taking too many worms along with it.

Can Worms Live Outside The Bin?

No matter how you harvest your worm compost, you will surely end up with a few worms mixed in. If you are using the compost for potted plants, pick the worms out as you find them and return them to the bin as they probably will not do well living in a potted plant.

If you are using the compost in your garden, just leave them be. They will do fine in the garden indefinitely if you live in a temperate area that does not freeze.

If you live in a very cold area, they won’t survive the winter; however, they’re sure to enjoy their brief and exciting life outdoors, and you will still have a worm farm full of red wigglers.

How Do You Use Worm Compost?

This rich, free soil amendment can be mixed in with garden soil or potting soil when planting. You can also use it as a top dressing for potted plants, containers, and gardens. [source]

Compost and Compost Tea Enhance Your Garden Naturally

Experienced organic gardeners have always known about the disease and pest suppressing qualities of high-quality organic compost and compost teas.

Today, a number of scientific studies are backing up this anecdotal evidence.

High-quality compost provides a rich substrate for beneficial organisms such as actinomycetes, fungi, and bacteria to grow in abundance, enabling these organisms to consume and crowd out undesirable organisms.

Furthermore, these beneficial microorganisms produce enzymes and antibodies that also help thwart the efforts of disease organisms. It takes a very small outlay of cash and time to enjoy all of the benefits and uses of compost tea.

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