Worm Bin Leachate Scare

E-mail from Shelly:

Help! I may have just poisoned my whole garden and I’m panicking. I noticed too late – after feeding all my leafy greens – that my worm tea stinks and these white wriggling things pour out of the spigot – I have a video i can send through. it looks like larvae or something . I also watered my lemon tree with it.

I just fed my garden with this gross mess – what I now read is leachate rather than worm tea. I watered the garden with it before noticing how gross the leachate/tea was, and I hope I haven’t introduced something terrible. What should I do? Should I avoid eating this crop? Can I treat this somehow?

Hi Shelly,

This is definitely an important/interesting topic that inspires a LOT of debate – so thanks for writing in! On one side you have people who say that leachate is horrible, awful, poisonous stuff that should never be used. On the other side you have the folks that swear by it, saying it is liquid gold for their plants.

My own take on it tends to fall somewhere in the middle. Here is a run-down of my thoughts on the matter:

1) I do NOT like the fact that various worm bin manufacturers (and those that promote/sell their products) claim their bins provide a great way to produce high quality “tea”, even sometimes encouraging people to actively make it by pouring water down through the active system. This is misleading at best, and gives a lot of people the wrong idea about what (good quality) vermicompost tea actually is.

2) The liquid that ends up in the reservoir of a stacking system (these are the most common systems with reservoirs) can indeed end up being pretty nasty, anaerobic, phytotoxic stuff, and my feeling is that this stuff should be treated with caution. We will come back to this.

3) The reason I’m not totally “anti” leachate like some people is the fact that the age of the system can play a major role in determining the overall quality of the drainage liquid. Leachate from newer systems has a lot more potential for creating issues, whereas leachate from really mature systems will usually be something much closer to an actual tea since there will be a lot more finished (stabilized) compost for the liquids to percolate through.

SO…my overall recommendation for people with these bins is to take advantage of any liquids that do drain down. I feel these should be diluted (ideally) with rain water or aged tap water and used in larger gardens rather than potted plants. If the leachate is really foul smelling perhaps just pour onto an outdoor compost heap or dilute and use for trees/shrubs.

I DO NOT recommend adding water to these systems at all (assuming plastic). They retain moisture very well and regular flow through of additional water only serves to make the environment more soggy and to reduce the beneficial qualities of the compost being produced.

You are far better off making really nice quality vermicompost (aka “castings”) in the system over time and then harvesting it and using that material to make teas. It will be much better stabilized – without the phytotoxic compounds that can end up in leachates – and full of beneficial humic (etc) compounds that will help boost plant growth.

In your case, Shelly, obviously what’s done is done. I am glad you dumped it into a garden and not some container plants – that should help. Maybe just water well to help dilute any concentrations of phytotoxic compounds that may be present in the soil. Microbes will help the process along as well.

You definitely don’t need to worry about anything super toxic or something that could make crops dangerous to eat. If you were using fresh manures there could be pathogen risk, but this is unlikely in a regular worm bin (fed typical fruit/veggie scraps etc) leachate.

Time is your friend as well – and I’m sure all will be fine overall. Next time around, I suggest diluting it quite a bit before use (especially if it has a strong, foul odor).

As for the white wriggly things, those are almost certainly springtails – and are absolutely nothing to worry about. They help with the composting process, and it is not uncommon at all for them to end up in the reservoir (especially in cases where people are actively watering these systems).

Hope this helps!

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    • Andy Loy
    • September 12, 2021

    I 100% agree with you. Leachate is not worm tea or extract. I don’t like how some worm bin manufacturers promote their products to produce leachate as worm tea.

    There is one worm business in Puerto Rica that makes leachate the right way as I call it. The worm farmer let his worm bins go to 100% vermicompost, then add water to drain a few times over the finished vermicompost. A neat but long process. The company name is West Knight Worms. John Kohler of Growing Your Greens made a video on West Knight years ago.

    • Bentley
    • September 12, 2021

    Hey Andy – thanks for chiming in!
    I remember John’s video about the operation in Puerto Rico – need to revisit that one. I seem to recall he was raving about the stuff.

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