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Compost Tea: Organic Lawn Care Miracle or Myth?

Compost tea has been generating a lot of buzz and controversy in the world of lawn care. It is used to inoculate soil and foliage with beneficial microbes and is being touted as a cure-all for poor soils and a natural protection against lawn diseases. Landscape firms, grounds managers and homeowners are applying it as a key ingredient in their organic lawn care programs.

Compost Tea - Cartoon of floating tree in wate

What they are saying:

  • "Better than plain old compost"
  • "Increases plant growth"
  • "Keeps lawns and garden plants free of disease"
  • "Speeds the breakdown of toxins"
  • "Eliminates toxic chemical use"
  • "Shown to increase the nutritional quality and improve the flavor of vegetables"

There is no denying the benefits of compost or the importance of healthy soils teeming with beneficial microbes; however, is compost tea worthy of all this praise? Or...is it just another gardening remedy promoted as having amazing properties but doesn't really do much of anything?

What is Compost Tea?

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CT is a liquid extract of compost that contains beneficial microorganisms and nutrients. I have heard it defined as a liquid suspension of biological life.

In a nutshell, it is made or 'brewed' by placing compost in a permeable bag and then soaking it in water 24 to 48 hours. There are recipes that include additions of molasses, fish hydroslate and other sources of nutrients. Air is then pumped into the brewer to promote the growth of beneficial, aerobic microorganisms. The tea is then applied to the soil or as a foliar spray.


Foliar Application of Compost Tea

Foliar application to prevent fungus diseases

Harvard Uses It!

Below is an interesting video (2009) demonstrating how Harvard Campus Services has integrated compost tea into their organic landscape management plan. Wayne Carbone, the head groundskeeper at Harvard, states that CT has helped them "eliminate all synthetic fertilizers and all harmful chemicals".

Organic Landscaping as seen on "Ask This Old House" from Harvard Campus Services on Vimeo.

As a bonus, the guys from "Ask This Old House" share a very creative brewing and application technique at the end of the video that is perfect for do-it-yourself homeowners. Converting a rain barrel into a tea brewer is a great idea!

This rain water collection system could easily be converted into a tea brewer
Compost Tea Brewer utilizing collected rainwater

Bio..Logical Lawn Care or Snake Oil?

The noble pursuit to eliminate the use of synthetic chemicals in lawns and gardens has whipped up an onslaught of elixirs and home remedies that do not work. Whenever I encounter a product or home remedy that seems too good to be true, I search for what the experts are recommending.

In this case, The Garden Professors, Linda Chalker-Scott and Jeff Gillman, state that there is no benefit to applying compost tea.

As researchers and professors, they base their recommendations on what the research supports and they point out that the science behind compost tea is lacking. Gillman calls it "Voodoo Science" in his blog post about Harvard's Organic Landscape Program.

So why are the people at Harvard raving? Well, it looks to me like they did a bunch of good things, incorporated one Voodoo science technique, and then attributed an inappropriate amount of their success to the Voodoo science technique. Go Harvard!

Compost Guru Frank Gouin, agrees:

“It’s very hard to find research that supports compost tea” as a disaese suppressant. And even for its nutrient-providing benefits, Gouin thinks that regular compost is better."

~ Homestead Gardens Blog January 2010

I'm 100% behind reducing chemical use in lawns and landscapes and welcome new ideas and innovations. However, until there is scientific proof that compost tea actually does what supporters claim, I will stick to simply topdressing my lawns with compost and adding fertilizer to supply nutrients.

Compost Tea


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