A brief rebuttal from Jeff G. (Comment here!)


After reading Jeff’s response I don’t have a lot to add. I’m simply more cautious regarding human pathogens and think that, based on current research, even the best made compost tea has the potential to spread these pathogens in a worst case scenario. That no one has reported to have been poisoned yet does not mean that no one has ever been poisoned (this type of poisoning is notoriously underreported), nor does it mean that no one can ever be poisoned. Additionally, I’ve learned the hard way to be extremely skeptical of claims and testimonials and I simply don’t accept that something works because someone says so unless I’ve seen exactly how conclusions were reached —I don’t care if we’re talking about a backyard gardener, a professor with five Ph.Ds or the President of the United States.

So, probably the best way for me to conclude is by adding my voice to Jeff’s calling for more testing of these compost teas—both for the presence of human pathogens and for their efficacy—and by pointing out that, in my opinion, the home garden is not the place to run these experiments.

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Elizabeth Licata

Elizabeth Licata has been a regular writer for  Garden Rant since 2007, after contributing a guest rant about the overuse of American flags in front gardens. She lives and gardens in Buffalo, N.Y., which, far from the frozen wasteland many assume it to be, is a lush paradise of gardens, historic architecture, galleries, museums, theaters, and fun. As editor of Buffalo Spree magazine,  Licata helps keep Western New Yorkers apprised about what is happening in their region. She is also a freelance writer and art curator, who’s been published in Fine Gardening, Horticulture, ArtNews, Art in America, the Village Voice, and many other publications. She does regular radio segments for the local NPR affiliate, WBFO.

Licata is involved with Garden Walk Buffalo, the largest free garden tour in the US and possibly the world, and has written the text for a book about Garden Walk. She has also written and edited several art-related books. Contact Elizabeth: ealicata at yahoo.com


  1. I recently completed the “Organic Landscaping” course offered this year for the first time in the U.S. Department of Agriculture Graduate Program. Use of compost tea was enthusiastically recommended with the words, “I don’t know how it works. But it works!”

    Part of the course involved a tour of Pogo Organics, a huge for-profit composting operation outside Washington, D.C., that has evolved from a family tree service business. Pogo Organics has gained quite a reputation on the East Coast for its work with soil organisms and specifically manufacturing and applying compost teas. And, yes, the organisms in question are aerobic, meaning they must be grown in water using a pump to aerate the water, much as you would do with your home fish tank. The microbes need dissolved oxygen to survive for any length of time.

    Pogo uses several large barrels. Compost is placed in fabric bags–just like big tea bags–which are then suspended in the water, a form of powdered carbohydrate is added for the organisms to feed on and the pumps are turned on. The microbes multiply. After aeration, the liquid must be used quickly before the organisms suffocate and die.

    Myself, I have not used compost tea. I am contemplating starting a compost tea operation, not terribly difficult to do if you have a few pieces of required equipment. I agree that research should be conducted and standards applied. Meanwhile, when I hear serious gardeners and arborists insist that compost tea works wonders, I have to believe them. I also agree that compost tea applications should be augmented with compost to feed the microbes.

    You can find Pogo Organics at http://www.pogoorganics.com/.

    Other resources: http://www.amazon.com/compost-tea-brewing-manual/dp/B0006S6JVK/ref=pd_bbs_sr_1/103-5917475-2938220?ie=UTF8&s=books&qid=1182344297&sr=1-1

    Our USDA “Organic Landscaping” course was largely guided by standards promulgated by the Northeast Organic Farming Association. Those standards make no firm claims or judgments either way on the effectiveness of compost tea. What they do have to say is:

    “Compost tea is attracting increasing attention as an inoculant to enhance or restore soil and leaf surface microflora…Caution: There are a lot of variables involved in creating high quality compost tea, therefore it is important to understand the process thoroughly before attempting to make or use compost tea.”

  2. Now this is the kind of stuff that bugs me a little. This post was started with the quote “I don’t know how it works but it works” and concluded with a quote which reads, in part, “it is important to understand the proces thoroughly before attempting to make or use compost tea.” These statements are largely (though admittedly not completely) conflicting.

    I don’t use pesticides whose mode of action, breakdown products, and cancer/disorder causing potential I can’t research and that goes double for homemade brews which contain who knows what and which will, in all probability, vary considerably from one batch to the next.

    I am curious though, who was the person who gave the talk for the USDA? Was it a person with a vested interest in the success of compost tea or a nonpartisan researcher?

  3. I’m a landscape architect who professes no great knowledge of organic maintenance practices, but I do design my clients’ gardens to thrive based on the specific conditions of that site. And to clarify, I’m mostly about native and Mediterranean plants for the southern California area.

    But I have a client who has been applying compost tea made by a local entrepeneur for quite a few years. As others have already pointed out, they swear by the application of compost tea and the garden looks ab fab most of the time. But the skeptic in me has to ask “what proof do you have?”

    We don’t have identical gardens growing alongside this one that is used as a control – one garden gets the tea, another is sprayed with Red Bull, and one goes without.

    I would very much welcome some definitive studies and conclusions from the Jeffs. This has been a great feature for Garden Rants and I encourage you to keep poking away at our dearly held beliefs. BG

  4. I am on the Alaskan Jeff’s side. We all know that compost is not compost is not compost; there are infinite differences depending on the inputs. However, I have trouble worrying about E. coli when I use a commercial compost made exclusively from leaves. How do human pathogens get into the leaf mold? I have made tea using worm castings from worms I have fed with kitchen scraps. Here I do not know whether e.coli can work it’s way through a worm’s gut, but it seems a bit unllikely especially since I follow the basic rules of composting using only vegetable matter and no meats or dairy products.

    In the end, leaf based compost should be free of any pathogens. Dr. Jeff – do you agree?

  5. Not any more! There is a waiting period sometimes for comments to appear. And please let us know if there is difficulty posting comments.

  6. Gotta love the echo effect!

    Sure, I agree — with a few caveats. The type of materials that you mention using are unlikely to contain human pathogens — if they are pure. Are you absolutely sure that there is no fecal contamination? I mean absolutely sure — no question at all? Studies have shown that E. coli in particular can live a year or more in poorly composted materials. Remember that bacteria are also very small and easily transferred by unclean hands. Did anyone touch your compost or brewing apparatus who didn’t wash their hands the last time they went to the bathroom? Are you using molasses which can allow these bacteria to multiply very rapidly?

    Remember that undetectable (but nonetheless real) amounts of bacteria can multiply rapidly in the right situation and pose a danger.

    All this said — if you’re going to use compost tea then using the compost materials that you mention along with Jeff L’s brewing recommendations seems the safest option.

    One other quick comment. I do, personally, know people who think that compost tea is the best stuff ever. But these people tend to be very good gardeners who do all the right things anyway (good fertilizer, irriation, and land conservation practives). And it becomes very difficult to separate where the effects of good gardening practices ends and the effects of compost tea begin.

  7. Dang. We sure do have some impressive guests on this here site. Seriously, you guys should go on the road together.

    First, it sure doesn’t seem like it would be too hard to run some greenhouse tests. Get some good compost tea, test it against plain water and maybe an organic liquid fertilizer with a similar nutrient makeup (NPK, etc) and see what happens?

    Second, could Jeff L. comment a bit more on the brewers that simply chop up the fungi rather than add air bubbles? How do I know which kind I’ve got?

    And third–Ed, I totally wanna hear more about the USDA’s graduate program. Far out!

  8. Given the recent E coli problems even on organic produce, how can anybody be really sure vegetable matter isn’t carrying E coli? Are you sure those dusty potato peels you just tossed in the compost bin aren’t carrying something in the dirt from whence they came?

    Plus, with the number of birds, squirrels, possums, skunks, cats, dogs, etc. etc. in the neighborhood that wander in and out of the yard at will, I can hardly believe I can keep the garden soil “clean” by avoiding manure. If it isn’t E coli, it’s definitely something else.

    My biggest objection to stuff like compost tea is it is too much work. I have made many batches of homemade beer, and the cleaning, sterilizing, and temperature control for something like Toad Spit stout is definitely worth the trouble.

    But I have better things to do with my time than bubbling air through a tea bag full of compost suspended in water (or whatever it takes) even if it works like a charm.

    If the plants can’t make it without that kind of help, I’m afraid I don’t want those plants in my garden.

  9. There are plenty of remedies whose exact mechanisms we can’t fully explain yet we use them anyway. And westerners laugh at folk healing because it can’t be proved scientifically, yet for others it works just fine.

    All of which is to say, simply, that there is not an industry or infrastructure for compost tea–not yet, anyway, so no one is funding large studies and the evidence for it is perforce anecdotal and coming from here and there. It is a highly perishable product (Pogo Organics is working on a dry powder version that can be activated with water) so it’s not something you can just buy and stash on the shelf in your garage next to your box of Miracle Gro crystals.

    Yet the people who advocate it are serious, experienced people who insist it works wonders. Perhaps not something you would spray on your plants weekly. But if you are in the business of rescuing trees, for instance, and nursing them back to health, you might very well learn to appreciate the healing effects of compost tea. Or perhaps you would use it on your lawn occasionally rather than dousing it with Turf Builder.

    And, no, the instructor of the USDA’s “Organic Landscaping” course is not a compost tea salesperson, her name is Catherine Zimmerman. She grew up on a farm in Ohio, I believe and now is a professional landscaper who was certified in organics through the Organic Land Care Committee of the Northeast Organic Farming Association, if I’m not mistaken.

    You can view Catherine’s accreditation information here: http://www.organiclandcare.net/AOLCP/MD.php

    But like I said, I have not used compost tea and don’t claim to be an expert. Just someone who knows a lot about composting and soil ecology, has heard the testimonials and is intrigued enough to try making compost tea and using it.

  10. I’ve only had time to skim all this quickly. But it seems to me that the main benefit of compost teas is as a soil inoculant to ‘heal’ damaged soil by providing a source of microbes. Kind of like planting microbial seeds.

    So if anyone studies this, I’d like to see experiments conducted on ‘damaged’ soils, and I’d like to see them tested on ‘healthy’ soils. I’m guessing that in beds that I’ve regularly mulched and added compost and other organic matter to, any inoculation from the tea would be overwhelmed by the existing microbial community.

    I don’t think that I would personally invest in the equipment to make this myself. And unless I can see a clear benefit, I’m not likely to spend money to buy a commercial product that has to be made correctly and stored, shipped and applied in a way that maintains the microbial population until it gets into my soil.

  11. All great comments and discussion and the only comment I disagree with is the one made by Jeff G. that ‘the home garden is not the place to run these experiments’. I am sure that he meant in the context of scientific data but the whole interest in compost tea stems from the backyard gardeners’ success with the tea and the thought on the part of the manufacturers of the product to make a buck from the masses. My grandfather did, in fact, suspend a bag of manure in a barrel of water and then use the diluted product on his vegetable garden. Not something recommended now but when money was scarcer the home gardener used what he had and he had plenty of manure. Oh, no one died either. I guess this is my family’s ‘dirty little secret’.

  12. Mr. Jeff L.:
    How and how long do AACT organisms survive once they are deposited into the terrestrial environment of soil, since they originated in the aquatic environment of a tea?

  13. People terrified by the prospect of E. coli have to find a way to distance themselves from their own gut.

  14. Would you like to know what comprises “compost tea” at my house? Well, compost tea at my house is what happens when I buy a clear plastic box of pre-washed organically grown salad greens at the grocery store and then don’t eat them before they go bad. They begin to liquefy in the box, visibly, so I take the box outside, put it on my balcony, and allow the liquefaction process to complete naturally. Then I pinch my nose shut, open the box, and pour the liquid on my plants. It is exactly the color of oversteeped Oolong.

  15. Jeff, we met at the ELA show this spring, I was with Kevin Richardson. This is something that was written 4 years ago.
    I rest my case
    Root colonizing bacteria (rhizobacteria) that exert beneficial effects on plant development via direct or indirect mechanisms have been defined as plant growth promoting rhizobacteria (PGPR). Although significant control of plant pathogens or direct enhancement of plant development has been demonstrated by PGPR in the laboratory and in the greenhouse, results in the field have been less consistent. Because of these and other challenges in screening, formulation, and application, PGPR have yet to fulfill their promise and potential as commercial inoculants.

    Plant growth in agricultural soils is influenced by a myriad of abiotic and biotic factors. While growers routinely use physical and chemical approaches to manage the soil environment to improve crop yields, the application of microbial products for this purpose is less common. An exception to this is the use of rhizobial inoculants for legumes to ensure efficient nitrogen fixation; a practice that has been occurring in North America for over 100 years. The region around the root, the rhizosphere, is relatively rich in nutrients, due to the loss of as much as 40% of plant photosynthates from the roots. Consequently, the rhizosphere supports large and active microbial populations capable of exerting beneficial, neutral, or detrimental effects on plant growth. The importance of rhizosphere microbial populations for maintenance of root health, nutrient uptake, and tolerance of environmental stress is now recognized. These beneficial microorganisms can be a significant component of management practices to achieve the attainable yield, which has been defined as crop yield limited only by the natural physical environment of the crop and its innate genetic potential.

    The potential environmental benefits of this approach, leading to a reduction in the use of agricultural chemicals and the fit with sustainable management practices, are driving this technology. Recent progress in our understanding of the biological interactions that occur in the rhizosphere and of the practical requirements for inoculant formulation and delivery should increase the technology’s reliability in the field and facilitate its commercial development.

    An important aspect of colonization is the ability to compete with indigenous microorganisms already present in the soil and rhizosphere of the developing plant. Our understanding of the factors involved in these interactions has been hindered by our inability to culture and characterize diverse members of the rhizosphere community and to determine how that community varies with plant species, plant age, location on the root, and soil properties.

    PGPR that indirectly enhance plant growth via suppression of phytopathogens do so by a variety of mechanisms. These include the ability to produce siderophores that chelate iron, making it unavailable to pathogens; the ability to synthesize anti-fungal metabolites such as antibiotics, fungal cell wall-lysing enzymes, or hydrogen cyanide, which suppress the growth of fungal pathogens; the ability to successfully compete with pathogens for nutrients or specific niches on the root; and the ability to induce systemic resistance. Biochemical and molecular approaches are providing new insight into the genetic basis of these traits, the biosynthetic pathways involved, their regulation, and importance for biological control in laboratory and field studies.
    Compost tea is where its at
    PGPR is specific and exactly where it suppose to be when its needed

  16. I forgot to include the author, apologies
    Louise M. Nelson, Vice President (Research), Okanagan University College, 3333 University Way, Kelowna BC V1V 1V7

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