The Worm Dude
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Interesting Reader Questions!

I am planning to use vermiculite in my raised garden bed for growing vegetables, and would like to know if it will harm earthworms?

By the way, regarding the worm casting you sell, is it 100% pure casting?

What they sell at OSH, labeled, “black gold”, is mixed with peat moss and compost.


Vermiculite in “Normal” quantities (Say 10%-20%) does not harm worms. I know this because my container planting mix contains worm castings(usually with worms), peat moss, vermiculite and/or turface, compost, and biochar. When I repot my plants, the mix is full of happy worms.

You need to make sure that the rest of your garden bed material is worm friendly though. A treatment of synthetic fertilizer would make your mix NOT worm friendly, and some may believe the worms were harmed by the vermiculite.

Regarding “Pure” castings. In 7 years in this industry, I have NEVER seen “Pure” castings. Frankly, the science behind growing worms would suggest there is no such thing as “Pure” castings. Don’t get scammed.

Because worm castings can get really muddy, trying to raise worms in castings is not a good idea. It’s really easy to cut all the oxygen out, and you want a bedding that is fairly light so that it breathes. If raising worms in castings is difficult, surely keeping worms in castings long enough so that they’ve eaten all of the other material would make raising worms difficult.

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