The Worm Tea vs Leachate Conundrum

Something that seems to come up over and over and over (and over) again in e-mails I receive is this idea of removing “worm tea” from the bottom of a vermicomposting system. It just so happens that I was having my cartoon guy work on a “Hamlet Tries Vermicomposting” funny for me, so I thought WHAT BETTER TIME to put together a mini podcast on the topic.

Here is the quick and dirty summary:

– The liquid that drains from a vermicomposting system can be called whatever you want to call it – and yes “worm tea” is perfectly fine – but it’s important to realize that this is leachate that has drained down through decomposing organic matter. It’s definitely NOT the same thing as vermicompost/castings tea.

– When a system (whether stacking, single-compartment flow-through, or regular plastic tub with drain holes) DOESN’T produce leachate this shouldn’t be viewed as a bad thing. In my humble opinion this is actually what we should be aiming for! I’d much rather conserve my nutrients and produce a top notch vermicompost than be constantly collecting run-off from my systems.

– Vermicompost/castings tea is created when you submerge high quality vermicompost in water (preferably not straight from the tap) and either let it sit and steep or vigorously aerate it. It is beyond the scope of this post to get into a debate about the merits of aerated vs non-aerated teas, or any other the other numerous issues people seem to have – but if you are looking for more, you may want to check out this post: “Is Compost Tea Just a Fad?” (the fact that there are 78 comments should tell you something! lol).

– Leachate CAN be used as a liquid “fertilizer” of sorts, but the quality will be highly variable – depending to a large extent on how old the system is and how well maintained it is. Liquid coming from mature vermicomposting system that has been well maintained will likely going to be much better quality than a brand new worm bin operated by someone who is not all that familiar with the fundamentals of vermicomposting.

– Because the material the liquid is draining from will be at varying levels of decompostion (and aerobicity), there can be all manner of different compounds (some of them potentially phytotoxic or worm-toxic) being added to the “tea”.

– I recommend diluting any liquid that comes from the bottom of a worm bin – and potentially even aerating it for a period of time before use. I would also recommend only using it in your garden (vs small potted plants) just to be on the safe side.

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  1. Great Post Bentley!

    I just started an experiment the other day with leachate. I took a five gallon bucket that had about 3 inches of liquid in it, from the bottom of the bucket. I added some fox farm worm “tea” fertilizer, some bat guano for flowering plants, and some fresh rabbit droppings right out of the cage. I added 2 gals of distilled water and two airstones for aeration, to help the beneficial bacteria/fungi/microbes brew.

    It will brew for 24-48 hours depending on foam/froth levels, then be further diluted before being fed to various indoor and outdoor winter gardens.

    Surprisingly, the Roma tomatoes in my garden that were fed this leachate survived 30 degree weather that wiped out all of my other tomato gardens. Even more surprising is how fat these tomatoes are and healthy looking. I’ve never had a tomato plant survive a winter in Central California so it will be interesting to see how this all turns out and if the plant will thrive or die.

    On my blog I posted the effects leachate has had on my various gardens to my surprise.

    • Lobster Pot
    • November 22, 2012

    I am also in need of more info on molds in my worm bin, and compost tea. I brewed up a gallon of tea, according to reliable instructions, and fed it to my indoor plants. What a problem this has produced! I have yellow mold (and yellow mushrooms) coming out of the bottom holes of the pot (5 gallon). It has appeared to have stunted some the plants, and the root system does not look very good also. I also had some grey mold on top of the soil. I really want to use tea for my plants – it’s so healthy! But now I’m afraid that I am killing the plants with this worm tea. Help please!

  2. Lobster pot:
    The yellow mold you are describing is common n plants that are overwatered and aren’t getting enough air flow. I recommend adding some air holes to your soil by taking a metal object that is long like a straw and just poking holes in your top soil, as well as in the bottom near the drainage holes.

    The white/grayish mold is probably Mycelium, a natural occurring mold that is both healthy and beneficial to the breakdown of soil into food for worms. I wouldn’t worry about it. Be sure to keep indoor gardens at the proper humidity level as anything over 60% humidity typically leads to mold. Good luck!

  3. Hello,

    the debate if the excess liquids that are running out of worm farms are beneficial or not and if they should be called worm tea or not seems to be going around the world! Having been farming worms now for more than 15 years I made lots and lots of experiments! Many went well, others not !

    I believe that the run offs of worm farms can be beneficial for plants but the quality of it depends

    1) on the contents of the worm farm. The amount of worm castings and the amount of unfinished worm food inside the bin. The bigger the ratio of worm castings to worm food the nutrient richer the leachate from the worm farm should be.

    2) The amount of water that has been poured over the bin will determine the concentration of nutrients in the liquid produced.

    3) The more often water is poured over castings inside a worm bin the more of their valuable nutrients will be washed out, making the leachate as well as the castings less potent over time.

    Nevertheless we achieved good results with worm leachate and could clearly see the positive impact it had on the plants we used it on but

    when we started to brew “proper worm tea” using pure undiluted worm castings and molasses in the process we where blown away by the results.

    In my humble opinion there can be no doubt that a freshly brewed worm tea is clearly much more beneficial for plants and soil than any run off liquid from even the best of worm farms.

    We brew our worm tea for 24 hours and usually use it within 6 hours once it has matured.

    Best regards


    • marty
    • June 11, 2013

    ..i use leachate when im too lazy to make tea 🙂
    this time we collected all the house plants, set them on our two large worm bins and watered away.
    I collected the run off, added molasses, air, and a tiny sub pump from my cats water
    I have a feeling ill get an awesome response..especially from the lemon balm.

    • laurel
    • January 26, 2014

    I understand brewing proper tea is the best way to go but I also collect leachate throughout the winter. Does freezing this liquid dilute its effectiveness?

  4. Hi Laurel,

    I am pretty sure that the freezing leachate will kill the beneficial microorganisms in it and it will definitely loose some of its effectiveness.

    Nevertheless give it a try next spring and compare it in an experiment against plants that are treated with fresh leachate.

    Happy worming

    • Teresa
    • February 8, 2014

    Hi Laural,
    Did you ever find out if freezing leachate actually would hurt it?

    Has anyone ever tried it first hand and found out if it would hurt the leachate or not?

    I am also getting my first greenhouse this spring. Does anyone know if it would be a good or bad idea to put my worm bins in the greenhouse when I get it? I don’t want to make it filled with mold or fruit flies.

    We just adopted a worm bin last week from a friend of ours and that was not so good. She was not taking care of it, I don’t know what she was feeding it or when she fed them last, but that thing stank so bad and was actually dripping with stuff that looked like mud and had tons of little white worm everywhere. My husband and I spent 6 hrs getting rid of everything we could git rid of including gnats or fruit flies, cleaning it out and saving as many worms as we could, and cleaning the bin. I am still finding some gnats or fruit flies but I think I pretty much have it taken care of. All I can say is at least those worms have a better home than what they had!!!

    Any suggestions on anything I will take!!!

    • Teresa
    • February 8, 2014

    I have been throwing my leachate down the toilet. I have been told that it is not to be used in the garden or on plants. Only the tea and the compost. If you can use the leachate and if you can freeze it, please let’s get this cleared up. There are so many different answers to just one question. All we want is just the right answer.

  5. Hello Teresa,

    I understand your frustration :-(!

    Congratulations of saving your worm herd! If a worm bin smells bad there is certainly be something wrong. A healthy worm farm doesn’t produce bad odors.

    The little white worms where most probably “Spring-tails” and they are beneficial for your worm farm as they are helping to compost organic waste.

    Worm leachate is usually beneficial for your plants when the worm bin contains already a lot of worm castings. The leachate will absorb nutrients from the castings which can than be used as plant food. On the other hand if a worm farm contains mainly kitchen waste the leachate will be less beneficial. I suggest you give your worm farm about 2 month before you start producing leachate.

    You can place your worm farm inside a greenhouse as long as it doesn’t get to hot inside. Compost worms can handle a maximum temperature of 86 degrees F / 30 C.

    I hope this helps a little :-)!
    If you have further questions please feel free to ask!

    All the best and Happy worming.

  6. Teresa:
    “throwing my leachate down the toilet” is the worst thing you can do.
    You are right, there are many contradicting informations and experiences an I am personally not a big defender of worm tea, but just use it and make up your mind.
    Regards from Mexico

    • Opal
    • April 30, 2014

    I’ve been worm farming for over two years, and I’ve always used a single bin, no drainage holes. I frequently turn the bedding, monitor the moisture level, and either have a towel draped over the top (if I’ve had problems with gnats), or keep the lid off.

    My question pertains to leachate or seeping. I’ve never had liquid in the bottom of my bins.

    Nearly every worm blog out there has a post or video tutorial on how to create (or buy their) stackable bin system.

    Have I been doing it wrong for the past two years? If my bin is NOT producing this liquid stuff is that a sign I’m doing something wrong?

    I’ve wondered about this for a LONG time but have never asked anyone.

    • Bentley
    • May 6, 2014

    Hi Opal
    You are absolutely NOT (necessarily) doing anything wrong just because there is no leachate. I myself aim to never have leachate dripping from any of my systems.
    Obviously I can’t guarantee that everything is OK in your system (it could still be too dry, for example) – but I want to at least make it clear that having leachate dripping out is not some sort of proof of successful vermicomposting! lol

  7. Hello Opal,

    its perfectly fine to run a worm bin without producing leachate. You just have to make sure that your worm bedding stays always moist. Visualize the wetness of a squeezed out sponge. This is a perfect moisture level for a worm bin bedding. If in doubt rather have it to wet than to dry.

    If you take a hand full of bedding and squeeze it and just a few drops of moisture drip down than the moisture level is perfect.

    Happy worming!

    • Thomas Taber
    • December 25, 2014

    Good Morning All.
    I have two compost bins. One was a thought out planned concrete 7 foot tall bin with a run off that flows into a ( Now full ) 50 Gallon drum. The other was a thrown together partical board four foot by eight foot box lined with plastic. Everything that is biodegradable goes in that box, that is outside. Angled, to collect run off, I’ve added worms for the last two years. The fluid that comes from that box ( No aroma from the box or the tea ) will not freeze. I’m wondering if the fluid that comes from the compost box might be flammable.
    The I too have used it on newly planted bushes, flowers, trees and vegetables and tomato bushes that turned into Trees. Growing far above seven feet tall and sprouting new flowers and tomato’s way after 30 degrees.
    Can some one tell me why the contents if the tea will not freeze?

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