Homemade Compost Tea that Your Plants will Love

What is compost tea and how do you make it?

People like to drink tea for its health benefits and pleasant taste. Plants like tea as well – just a different kind, one that’s steeped in compost. Every seasoned gardener knows the benefits that compost has on the soil food web and the health of your garden. Compost tea provides your soil with a boost of millions of microorganisms without the trouble of applying actual compost. It’s relatively easy to make compost tea. Whether you decide to make it yourself depends on your time and willingness to try new gardening techniques.

What exactly is compost tea?

Photo Courtesy of Stephano Lubiana

Compost tea is brownish black, earthy smelling water, full of microorganisms that have multiplied many times over. It’s like compost in liquid form, but without the physical organic matter. The liquid form makes it easy to apply and can help keep your garden healthy.

Compost tea is made by creating the conditions that allow microorganisms to multiply quickly. Those conditions are oxygen and food, kind of like for you and me. But more on the specifics of how compost is made is below.

Why would you want to use compost tea?

Plant roots interact with soil microorganisms and form a mutual beneficial relationship. Plants provide food (exudates) to soil microorganisms in exchange for nutrients, minerals and protection from pests. The more life there is in your soil, the more nutrients your plants will have access to. Compost tea can provide a boost of life that reinvigorates the soil food web.

It can also be sprinkled on your plants which can help protect them from pests and diseases. The microorganisms in the compost tea act like a barrier between the plants and potential diseases that you want to avoid as a gardener. It’s kind of like a preventative pesticide, but without the negative side effects.

When would you want to use compost tea?

In early spring, your soil will be slowly waking up from a long winter slumber. If you put compost or mulch on your garden in fall, it may need to decompose a bit further before you plant your seeds or seedlings. By adding compost tea, the decomposition of the mulch or unfinished compost could speed up, and make more nutrients available to your plants.

Some gardeners use compost tea every week or so to ensure that there is an abundance of beneficial soil microbes. You can’t really buy compost tea in stores – not that I’ve seen – it can really only be made yourself.

How do you make compost tea?

Soil microorganisms need food and oxygen to grow and multiply. To get your compost to multiply you need to aerate your water somehow and provide food. Food is the easy part. Two or three caps of molasses will be enough for a standard 5 gallon plastic bucket. 5 gallon buckets are a common size and should be enough for a small backyard garden.

Aerating is trickier. You can either spend time or money to aerate your compost tea. If you don’t aerate the mix, the helpful microorganisms will die, and the anaerobic microorganism will take over. You’ll know if you haven’t aerated your compost tea enough if it starts to have an unpleasant smell. It’s supposed to smell earthy – like fresh compost.

The free way: aerate your mix of water, 2-3 caps of molasses and a few handfuls of compost by stirring together in a 5 gallon bucket with a long stick. You’ll want to stir it fast enough to create a vortex. The sloshing and movement of the water exposes the compost to oxygen. The major downside to this method is that you need to stir for a while to allow for the microorganisms to multiply.

The ~$35 way: Like everything in life, if you spend a bit more money and effort, you’ll likely end up with a better product. Instead of manually stirring together the ingredients, head over to a pet store and buy a fish pump that can make bubbles. You’ll need electricity for this and a space that has relatively stable temperatures. A garage is perfect.

What you’ll need to get and do:

  • Standard 5 gallon bucket
  • A fish pump with two air hoses and air stones that attach to the end of the hoses. Air stones create small air bubbles that are ideal for water aeration. This gear should cost around $35. Test out this gear before making compost tea to make sure it is distributing air bubbles evenly throughout the bucket.
  • An old nylon. Put a few handfuls of compost in it. Make sure the compost isn’t compacted in the nylon – keep it loose. This will be your compost tea bag.
  • Molasses: 2-3 caps full. Stir into the 3/4 full 5 gallon bucket.
  • Put the air stones at the bottom of the bucket after stirring.
  • Tie the nylon compost tea bag to a stick and lay it across the buck so the compost is immersed in the bubbling water.
  • Wait for 24 hours.

After 24 hours, the microorganisms will have multiplied and consumed most of the molasses in the water. This gives the compost tea a smell. If you’ve had enough aeration, it shouldn’t smell bad. It should smell earthy but not pungent.

The very last step is to pour your 5 gallon buck of compost tea into a watering can and water your garden with it. Your plants will thank you for it, and you will have learned a new, useful technique to keep your garden healthy.

By Nate Van Beilen