Harvesting a new batch of worm castings, plus an uninvited guest


You may wonder: when is a good time to harvest vermicompost from the lowest tray of  the worm house? Whenever the top tray starts looking this full:


And so this weekend was the time for me to harvest my second-ever batch of worm castings! I’m still super excited, even though it was not the first batch anymore 🙂

This time, the bottom tray was a bit soggy, probably because I got too enthusiastic with the ice cubes during the last heatwave (this keeps the worm comfortable, as I described in a earlier post). From now on I should use about 25% ice cubes and 75% ice packs to reduce the moisture, yet maintain the temperature. In any case, the tray was definitely ripe and ready for harvest.

The woody granules you see on top are BTI-infused particles I sprinkled on top of every tray a couple of weeks ago to control the fruit flies.

I transferred any worms lingering in this tray back into the worm house.


I also checked the bottom tray (where the compost tea collects) and carried over the single worm that was residing there.


Then I checked the second tray from the bottom and decided that it was ready for harvest, too (frankly, I just needed to free up more space in the worm house for all those watermelon rinds!). So I cleared this tray out, too.


So far, every tray of the worm house produces a 3/4 to full 3-gallon bucket of vermicompost. What can I say, a couple more harvests, and the setup plus the worms will have had paid for themselves!!!


When I checked on the third tray from the bottom, however, I was quite unpleasantly surprised: it was swarming with grubs… I believe I’m to blame here, because when filling this tray with food waste, I became obsessed with chopping it up in the food processor to save space. As a result, the mix became too gooey and very inviting to grubs. At least this is my hypothesis.


After silently cursing myself and my well-intended, yet poorly executed interventions, I went to the kitchen, grabbed a pitcher of soapy water and threw all the grubs I could find in there. Grubs are a larval form of insects from the beetle family, and while I don’t have any plants on my balcony that they could harm, all these grubs would eventually transform into adult beetles, who can fly away and lay new clutches of eggs, say under the neighbors’ roses. And roses are very susceptible to grub damage. So long story short: grubs had to take a dive, for future pest prevention.


Next step was to make this goopy tray habitable for the worms again. So to reduce moisture and add air, I covered the surface with a generous heap of perlite…


…followed by another heap of the “brown matter”.


As I was mixing the additions in, I felt the goop dissipate within a few seconds. Hopefully, this tray will be ready to harvest in a few weeks.


So in addition to harvesting a double batch of great vermicompost, I have learned some valuable lessons today:

  • Cutting up the food waste before putting it in the worm bin really does save space, but…
  • Pulverizing the food waste into fine pulp results in a gooey mass that is uninviting for the worms, yet very inviting for insect larvae, such as grubs
  • From now on I will only use my own hands and a knife to chop the larger fragments of food waste
  • If you do find one of your trays to be in a poor shape (too wet, too slimy, etc.), adding more “brown matter” and perlite (in particularly bad cases) will do wonders and restore the structure of your future worm castings.

I hope you find this information useful!



7 thoughts on “Harvesting a new batch of worm castings, plus an uninvited guest

      1. After spending two hours over several days I think I want to sieve. I was able to harvest, but it was hard with my setup. Which one do you have, qnd where on amazon did you find it? Do you only do one of the trays at a time? Which one. I have a 3 bucket sustem. Top holds holds food and browns on top, middle holds more browns and worms, nasement holds water that gets through and bricks. When is the latest you would weatherproof?


        1. https://www.amazon.com/gp/product/B018RU0BAS/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
          This is the one I have. I do harvest one tray at a time, starting at the bottom (the worms move up the stack as they process the scraps in one tray).
          I haven’t decided about weatherproofing yet – need to do a bit more reading, but there’s definitely no need as long as the temps are above freezing. I should probably make up my mind within the next couple of weeks, though…


  1. Pingback: Balcony garden update: plants, squirrels and a bad batch of vermicompost – The Fire Escape Garden

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