The most common another name for worm castings is vermicompost. You'll also see vermicast, worm humus, and plain worm poop on bags and websites. All these names describe the dark material worms make after eating food scraps and bedding.
I had a confusing time at my garden center the first time I shopped for castings. One bag said "earthworm castings." Another said "vermicompost." A third just read "worm humus." Prices went from $15 to $50 for what looked like the same dark stuff. I bought all three and tested them at home. They smelled the same and felt the same in my hands. They worked almost the same in my beds too. The worm castings terminology changes by brand, but the core product stays close across most labels.
A key difference hides between two of these terms though. Pure castings are 100% worm-processed material. Every grain passed through a worm's gut. The vermicompost definition is broader than you might think. It may hold partly broken-down bedding, food bits, and other organic matter mixed in with actual castings. Think of vermicompost as the full harvest from a worm bin. Pure castings are just the finished worm output with nothing extra.
Brands pick their own terms for marketing reasons. Brothers Worm Farm labels their bags as "earthworm castings" to signal purity. Urban Worm Company goes with "vermicast" on their bags. In research papers, the standard term is vermicompost. Most studies focus on output from Eisenia fetida, the red wiggler worm that drives most large-scale production. All these names point to the same basic product with small shifts in how it's processed.
Worm Castings
- Purity: Refers to material that has been 100% processed through a worm's gut with no leftover bedding mixed in.
- Where seen: Most premium retail bags use this label to show higher quality and support a higher price tag.
- Best for: Growers who want the most concentrated microbial and nutrient punch per pound of product.
Vermicompost
- Purity: Holds castings plus partly broken-down bedding and food from the worm bin, making it a broader mix.
- Where seen: Research papers and large farms tend to use this as the standard term for the industry.
- Best for: Soil building where bulk organic matter adds value on top of the castings themselves.
Vermicast and Worm Humus
- Purity: These terms often mean the same thing as pure castings, though meanings shift between brands.
- Where seen: Online shops and sellers outside the US tend to favor these terms on their listings.
- Best for: Same uses as standard castings. Just check the label to confirm actual purity levels.
When you shop, read past the name on the front of the bag. Look for products that say 100% pure castings if you want the strongest dose of nutrients and microbes. Bags labeled vermicompost may cost less. But the nutrient punch per pound drops since raw bedding dilutes the end result.
Don't let the name game stop you from buying. You're getting a solid organic product for your soil no matter which name sits on the front. Just check the details on the back of the package. That tells you far more about what's inside than the brand name on the front.
Read the full article: 7 Proven Benefits of Worm Castings
