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What is Compost Tea?

Gardeners and plant enthusiasts are always looking for natural, affordable fertilizers that promote growth and are environmentally friendly. The good news? It's probably already collecting at the bottom of your worm compost bin.

Compost tea is a liquid fertilizer made by diluting leachate (the liquid at the bottom of a worm compost bin) or soaking end-use compost in water. Often referred to as “black liquid gold,” compost tea promotes plant growth and significantly prevents disease​​ through a combination of nutrient enrichment and microbial activity. This organic liquid fertilizer is packed with essential nutrients like nitrogen, phosphorus, and potassium in a readily available form, providing plants with the building blocks necessary for robust development. The diverse community of beneficial microorganisms found in compost tea establishes a symbiotic relationship with plants. These microorganisms enhance nutrient absorption, foster root growth, and contribute to overall plant resilience. Some microbes in the tea also act as natural antagonists, suppressing harmful pathogens responsible for plant diseases. The synergistic effects of nutrient enhancement and microbial activity make compost tea an effective and sustainable solution for supporting plant health and vitality.

Brewing compost tea using an indoor worm compost bin is easy!

Materials Needed:

  • Collected leachate or well-composted worm castings

  • Non-chlorinated water

  • Large container with a lid

  • Stirring stick or spoon

Prepare Water: Fill the container with non-chlorinated water. Let it sit for a day to allow excess chlorine to dissipate.

Collect Leachate: Gather the liquid that drains from your indoor worm compost bin. This leachate is rich in nutrients. You can also collect a handful of worm castings (ensure there are no active worms in this) if you do not have leachate at the bottom of your bin, or if you use an in-ground system.

Mix Ingredients: Add the leachate or worm castings directly into the water. Stir well to mix.

Cover the Container: Place the lid on the container to keep contaminants out. However, leave it slightly ajar to allow air exchange.

Brewing Time: Let the compost tea brew for 24-48 hours, stirring occasionally. This manual agitation helps introduce oxygen.

Strain (Optional): After brewing, you can strain the liquid through cheesecloth or a fine mesh to remove (and then compost) any remaining solids. 

Dilute and Apply: Dilute the compost tea with water at a 1:10 ratio (1 part tea to 10 parts water). Apply the diluted tea to your plants as a soil drench or foliar spray.

Storage: Use the compost tea within 24 hours for the maximum benefit. If you need to store it, keep it in a cool, dark place.

Whether you're a do-it-yourself gardener or prefer a ready-made solution, compost tea has something for you. Commercial compost tea is available at garden centers and online, but DIY methods offer an economical and attractive way to prepare this beneficial tea in your own home, using your own food waste​​. Whether brewed at home or bought from the store, compost tea is truly a magical elixir for your garden, bringing a vibrant, thriving green space to your garden!


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