Mysteries of Invasive Worms Revealed


At least I HOPE they're revealed.  Because when I wrote here about my adventures in worm composting, commenters let me know that worms are invasive and we'd all better watch out.  And I've noticed that that's no isolated concern.  At DC's recent GreenFest the woman teaching vermicomposting was grilled on the subject – and didn't have an answer.  So I hit the books and the search engines and the answers I found are over on my blog

Photo credit:  Red Worm Composting.


  1. Susan, wonderful piece there over on that other blog. Can you tell me the source of that little stat about earthworms and farming–that the addition of worms can dramatically increase yields?

  2. I read your post, the story on your website the two websites referenced and I’ll be darned if I know why earthworms are considered dangerous.

    Other than the fact they are not native and have slightly different habits, what is the functional difference? Also, what on earth could you do about earthworms if you wanted to and why would you want to do anything?

    I always thought worms were a good thing and now I find out that I may be harboring illegal aliens.

    I can only think of one responsible thing to do. In the spring I am going to dig up as many as I can out of my compost area and all those I find when digging and put them into a worm proof container, maybe an old tin can. Then I will take these interlopers to that pond out back through the woods skewer them onto hooks and feed them to the fish. That ought to help.

    It’s a bother, but everyone should do their civic duty.

  3. Susan, I like how you untangle all that conflicting info into logical order–much like sorting the worm bin!

  4. When people start screaming about invasive species to me, I like to point out that honeybees, ladybugs, praying mantis and earthworms all have non-native invasive relatives living it up outside in the garden. Not to mention all the problems caused by bullfrogs, red foxes and Canada geese – all moved around by man into places they don’t belong. Places that have had them so long that people think they are native.

  5. Interesting info Susan, thanks.

    Jon asked what could you do about earthworms and why would you want to? Well, introduce moles but that opens up another “can of worms” (pun intended!”. I’ve heard that one drawback to lasagna beds is that the increased presence of worms sometimes ends up with an increased presence of moles to eat them, although I haven’t seen it in the 3 lasagna beds I’ve done. I agree with Jon. Why would you want to worry about that?

    I can’t imagine purchasing worms to add to regular outdoors compost. Part of the appeal of composting other than getting great organic matter is using free inputs.

  6. Hi Susan,
    This is a good summary of the topic. Just a reminder that those of us where the soil doesn’t freeze in the winter could have those red worms everywhere. I use regular garden worms in my outdoor compost and they do a wonderful job.
    Thanks for hitting the books for us.

  7. Ginny S said: “I use regular garden worms in my outdoor compost.” Do you buy these worms? If so, what are they called?

    I’m one of the millions of people with an obsessive personality (sorry for the pop psychology term but it’s a useful term). Of all the things I’ve been addicted to in my life, worm composting is certainly the strangest. Who knew when I bought my first pound o’ worms in March 2008 that I would become such a bore on the topic. Loved Susan’s summary!

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