Compost Tea

Compost tea is an organic fertilizer or tea “brewed” with mature, finished compost. Used as a root drench or a foliar spray, compost tea is an inexpensive and easy-to-make nutritional supplement for your plants.

There are two main types of compost tea: classic (non-aerated) and aerated. For both types, you must have mature compost (earthy-smelling, crumbly) and de-chlorinated water. Chlorine is purported to be harmful to beneficial microorganisms in soil and compost, which defeats the purpose of compost tea. So, it’s best to make compost tea with water without chlorine. The best water to use is rain water or non-chlorinated well water. If you don’t have access to non-chlorinated water, you will have to de-chlorinate it as much as possible. I’m not a chemist, so I can’t definitively state how to do this. However, several articles I’ve read have stated that leaving a five-gallon bucket of tap water in the sun for 24-48 hours will decrease the amount of chlorine in the water. I’ve read that aerating the water will decrease the chlorine more quickly.


Classic compost tea is made from compost and water. Fill a five-gallon bucket 1/3 to 1/2 full with mature compost then fill remainder of bucket with water. Stir well. Let sit for three to five days, outside, stirring daily. The longer it steeps, the stronger the tea. When it’s ready, strain through a burlap bag – or use a fine-holed colander – and apply, undiluted, to your plants immediately. Then, throw the solids from the straining process back into your compost pile.

If you wish to eliminate the straining process, you can make your own compost tea bag out of an old tube sock, cheesecloth, or a burlap bag.


Aerated compost tea adds aeration, a sugar substance, and optional supplements to the water and compost in order to increase the beneficial microorganisms and bacteria that grow in the tea.

The hardware needed is very inexpensive: five gallon buckets, a small aquarium pump, one aquarium stone per bucket, and aquarium tubing to go from the pump to the stone. Here’s my set up:

Compost aeration system

Compost tea aeration system

I used one pump for four stones by buying a T to split the tubing. However, I think I lessened the aeration that way. I’m going to get a second pump so I will use one pump per two five-gallon buckets.

As for what goes into the buckets, there are as many recipes for aerated compost tea as there are gardeners (search the internet). So here, I will share with you the recipe I use.

  • 3 large shovels of compost or enough to fill the bucket 1/3 full (You can also make a tea “bag” for this kind of compost tea as well. Your choice.)
  • 3 Tablespoons unsulfered molasses (sugar source)
  • 2 Tablespoons fish emulsion (adds additional nitrogen and micronutrients as well as additional food for the beneficial bacteria)
  • Water

Stir well and add aeration stones. Aerate three days, stirring daily. When it’s done, it will smell yeasty and have bubbles or foam on the top. Strain the compost tea (return solids to compost pile) and apply undiluted to your plants immediately.

Compost aerating

Compost tea brewing in my shed

Please note: Do not aerate longer than three days. Per articles I’ve read, the microorganisms begin to die off after that point. I think that may be true because one time I let it go five days; it smelled so bad I didn’t want to use it on any of my plants. Yikes! Also, while researching for this article, I read that even aerated compost tea should be made outside – in order to have access to the bacteria found in nature. I’m going to have to do it that way this year.

Because this is an organic fertilizer, you can’t “overdose” your plants on it. Use it once a week as a root drench, or put into a spray bottle to use as a foliar spray for additional help for your plants.

Although this is not a definitive article on compost tea, I’m hoping it will inspire you to try it in your own garden – whatever recipe you use.


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