Rock Hard Worm Castings

Here is a question from Joel:

I havested some castings but it was wet, I aired out the castings but
then it became hard as a rock. How can I get a nice crumbling casting
that is soft and not a rock hard castings that basicaly I can not do
anything with it?? please help.. Joel

Hi Joel,
Someone else recently asked the exactly same question so I thought it would make sense to write a response out on the blog. I’m sure this is something a LOT of people have encountered! I’ve certainly created my fair share of vermicompost cement over the years!

I don’t know what it is exactly that causes the material to solidify to effectively (the worm mucus perhaps), but I think some materials scientists should be looking into this – we could have the next revolutionary drill bit material on our hands here! haha

Seriously though, it is incredible how hard this stuff can get! I clearly remember the frustration of trying to revive a set of wooden systems I’d neglected down in my father’s basement. Not only could I not re-hydrate the material, but it was incredibly challenging even to break it up and get it out of the boxes!

Generally speaking, you are going to encounter this far less often with systems that receive frequent attention. The key here is to not let the castings get wet and then pressed together and allowed to dry. In the case of a flow-through system, my recommendation would simply be to keep things moving along – don’t just leave it to sit for a month or two at a time. I have learned this first hand with my first couple of Worm Inns (which can dry out fairly quickly as it is) – when I finally decided to dump the contents of these systems into an outdoor bin, the compost inside was pretty solid. I’ve encountered something similar with a wooden stacking system that I’ve used.

My current Worm Inn has materials packing down in the bottom (actually a good thing since it prevents everything from just falling out) but because it is being used so frequently, everything is staying moist and the vermicompost I’m scraping from the bottom is great stuff.

For those of you who are dumping out the contents of a plastic worm bin, my major recommendation would be to mix the material a LOT initially to break it up, then continue to mix and break it up on a daily basis. A small hand fork should work quite well for this task. As long as you can prevent large clumps of castings from staying pressed together while drying out, you should be ok!

Anyway – hope this helps!
Thanks for the great question.

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    • Alyssa
    • April 20, 2010

    Haha! I had the same question. My vermicompost from last fall turned to little rock hard balls over the winter, and now that I’m ready to use it, I have no idea what to do. I have another bin that’s ready to age – so I want to make sure not to make the same mistake again. I hope stirring it as it dries does help!

    For what to do with my new little rocks… After soaking for a few hours (still mostly rock hard – I even cut one with a knife and it was as dry as a malted milk ball in the middle), I then stirred a cup through a sieve. Took forever considering the amount, however I did end up with enough beautifully crumbly moist compost to make a container’s worth of potting soil.

    Any other ideas? I’m thinking these may just end up in the garden…

  1. I suspect part of the problem is the food you are feeding the worms. We produce tons of castings for commercial use/sale and have never had this problem. Be aware of the amount of water and the type of food you use. Perhaps try some composted horse/cow manure as food.

    We screen our castings with a tumbler type of device which separates the castings from any remaining compost food that was not eaten. The casting are granular in nature and not lumpy at all.

    Hope this helps.

    Dennis Copson, Nature’s Big Bud Worm Castings

    • Warren
    • May 11, 2010


    I am fairly new to the worm business and have been following this blog for a few months. My boys (ages 12 and 10) have joined me as well and we are having a great time. One question I have is regarding the frequency of turning the worms and their bedding. In the book “The Worm Cafe” they turn the worms weekly and indicate that they eat more and produce more castings because of it. On the other hand I have seen others on the web say that worms like to be left alone and should not be disturbed as often. What do you think?

    • Bentley
    • May 11, 2010

    Hi Warren,
    This seems to be a personal preference, when it comes down to it. I tend to fiddle with my beds a fair amount (use rakes etc to see what’s going on down below), but would never actually take the time to completely turn the worms/bedding in any sort of systematic manner. If you notice things getting a bit compacted, definitely loosen it up with a hand rake, and add some more bulky bedding.
    I think the worms will do ok either way (although I definitely WOULD leave them alone as much as possible if they’ve just arrived from being shipped), but i just don’t see the need to actually turn everything.

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