Worm Castings Tea – Part I

This week we will begin our exploration of the wonderful world of castings tea (aka ‘worm tea’, ‘vermicompost tea’, ‘vermi-tea’ etc). This is a closely related topic to that of worm castings (a subject we’ve certainly talked a LOT about as of late) given the fact that castings play a vital role in the creation of good quality worm tea, as you will soon learn.

On that note, the first important sub-topic we should probably look at is the ‘worm tea vs. leachate’ issue.

Unfortunately, there seems to be a lot of misinformation out there re: the definition of worm tea – I suspect that worm bin manufacturers/merchants (in particular, those selling ‘flow-through’ systems with ‘reservoirs’) are largely responsible, although there is plenty of similar info available on the web as well.

Bottom-line, the liquid that comes out from the bottom of your worm bin/bed is NOT worm tea – it is more accurately referred to as ‘leachate’.

The potential problem with leachate is that, while it DOES typically contain some beneficial compounds/organisms (the more mature your bin the better), it also can contain unstable materials leached from partially decomposed wastes. This in itself can be bad enough, since there are a lot of potentially phytotoxic compounds that can be created (during anaerobic processes).

The other issue is that since a lot of the stuff (for lack of a more technical term) in the liquid is not yet stabilized, it also will go anaerobic much more quickly if left to sit – thus creating an even nastier ‘tea’.

Don’t get me wrong here – I’m not saying that leachate can never be used as a sort of ‘tea’.

There are in fact plenty of people who use it successfully in this manner. What I WOULD suggest however is:

  1. diluting it with non-chlorinated water (more on that in a minute)
  2. aerating it with a simple aquarium air pump, tubing and an air stone, and
  3. generally putting it to use in outdoor beds.

The last one might not be quite so critical if you follow the first recommendations, but generally speaking, a large garden (especially one with rich, organic soil) will be better able to take care of any harmful compounds before they are taken up by the plants, than say the potting soil in a houseplant pot for example.

I mentioned “non-chlorinated water” – the reasons for not using water straight out of the tap should be relatively obvious. This water has been rendered fit to drink, and obviously one of the criteria there is an absence of microbes (pathogenic ones in particular). I don’t imagine chlorinated water would wipe out your entire population of ‘good guy’ microbes in the castings (not even close, I suspect), but why add set-backs of any sort when you don’t have to?

The good news is that chlorine can easily be removed from water – simply letting a bucket of water sit for 24 hours will do the trick, or you can speed up the process by aerating the water (as described above).

Ok – now that we’ve established what is NOT worm tea, let’s talk about what REAL ‘worm tea’ actually is.

By definition, worm tea is the liquid that results from the soaking of high quality (mature/stabilized) worm castings or vermicompost in water.

Generally, it is recommended that this water is aerated, and quite often other materials are added during the ‘brewing’ process to improve certain attributes of the tea, depending on your particular end use.

You certainly don’t have to add anything extra – and if you are jut starting out, it’s probably not a bad idea to stick to the basics and skip this step. As we’ll discuss in one of the other worm tea articles in coming weeks, there has actually been some controversy regarding the ‘feeding’ of worm tea microbes in this manner – in a nutshell, some feel that this can in fact increase populations of pathogenic microbes.

Something else worth mentioning…

While I have been pretty casual thus far about my interchangeable use of the terms castings and vermicompost (generally opting for the former term to keep things simple), the distinction between these terms is actually somewhat useful for this discussion.

As you may recall, vermicompost is a humus-rich material that contains varying amounts of worm castings, along with other decomposed or partially decomposed materials that have not passed through an earthworm’s gut.

Worm castings on the other hand are literally the ‘poop’ pellets that come out of the rear end of a worm.

From a ‘quality’ perspective, you should generally be striving for the highest percentage of worm castings you can achieve in your vermicompost (remember, it is next to impossible to have absolutely 100% castings, but you can get pretty close).

This certainly isn’t set in stone though – as we’ll discuss next week, this actually depends on your end use – not all types of plants respond the same way to different teas.

Some plants prefer teas with dominant fungal population, while others prefer bacterial dominance. As such, a vermicompost with a higher percentage of fungal food (such as carbon-rich ‘bedding’ materials) may indeed be better for creating a tea well-suited for certain types of plants than would pure worm castings (high bacterial dominance).

Ok – I think we’ve got the basics covered.

Hopefully this overview has helped to set the stage for what we’ll be covering during the next couple of weeks.

I’m sure you’ll be happy to know that next week we will be jumping right in to the real ‘meat’ of the topic – looking in more detail at how worm tea is made (including some DIY instructions), and how to best use it.

In our final worm tea newsletter we will talk about the beneficial properties of teas, and will highlight some of the research that has been conducted in this field.

Stay tuned! 🙂

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