Comfrey as Sole Food Source for Worms

If you’ve followed the blog for a number of years, you’ve likely seen some mentions of my favorite plant for vermicomposting – comfrey!

Not sure comfrey would be considered a weed – but it sure grows like one, sprouting up easily from even the tiniest little root fragment (funny irony is that it took me forever to get it established via seeds originally).

What I love about it – in comparison to most of the more typical weeds – is the abundance of lush foliage. A perfect “green manure” for any composting system – including one with worms!

I use comfrey a lot as a sort of “slow food” in my outdoor systems (eg vermicomposting trenches, vermicomposting planter, backyard composters). I just toss it in – maybe chop it up a bit if I’m feeling motivated – and usually cover it up.

There are claims that comfrey is actually a “dynamic accumulator” – collecting and storing nutrients that may be unavailable to other plants – but there does seem to be some debate about this. Regardless, it is a nitrogen-rich (and water-rich) waste – undoubtedly containing other valuable nutrients as well – that breaks down readily, and contains quite a bit of moisture.


Long-winded lead-ins aside, I thought it would be fun to try using comfrey as the ONLY food source (after initial set up) in a very basic plastic bin vermicomposting system. As much as I have used this material as a worm food, I have yet to try it as the only source of nutrition for an extended period.

Yesterday I got my bin set up very quickly. I started with a layer of moistened, shredded corrugated cardboard down in the bottom.

I then mixed in a small amount of “living material” – in this case older horse manure and straw.

Next, I added a modest amount of worm-rich material from one of my outdoor beds.

Finally, I added some comfrey, freshly picked from my yard. I made sure to chop it up really well, and also moistened it, since I want it to be available as a food source within a reasonable time frame.

This is going to be an open system (will come back to this in a minute) – my only “lid” will be a plastic bag sitting loosely over top.

Comfrey is a green plant waste, so some caution is warranted – especially in a small, plastic worm bin. These wastes can release ammonia during the initial breakdown process (very dangerous to worms) and may cause additional microbial heating. Please note that I set up a safe habitat for the worms in the lower half of the bin, layered the comfrey at the very top, and am using a very well ventilated system.

I definitely don’t recommend mixing green wastes (grass clippings would be another prime example) into the actual habitat zone – or even pocket feeding for that matter – in smaller systems (especially enclosed, plastic bins).

I am really looking forward to seeing how the worm population responds to this food source. Just to be clear – while the comfrey IS my only food source, it will still be important to keep things balanced with absorbent, carbon-rich bedding materials like shredded cardboard, so I will periodically add these as well.

Stay tuned!

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    • John Duffy
    • May 27, 2019

    I will be anxiously waiting to see how the Comfrey works out because I have an abundance of it

    • Curtis Windsor
    • May 30, 2019

    Excited to see how this turns out! Along with a comfrey patch I have a 15′ x 40′ alfalfa stand that I cut and dry for mulch and garden teas. Do you know if adding them dry would react any different in the bins?

    • Bentley
    • May 31, 2019

    John & Curtis – I know for sure already that this is a great food. But it will definitely be interesting to see what happens when it is basically the ONLY food source (other than bedding).

    Curtis – dried material has likely lost some of its nutritional value, but I’m sure it is still great stuff. Just need to be careful about amounts (likely not a big deal layered on top of a trench though) – will be a bit deceiving when dried.

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