Earthworms in the Forest

I was listening to one of my favorite podcasts last week and learned all about the invasion of the earthworms! This blog post is 100% inspired by this episode. I thought it was perfect timing considering my last post was about earthworms in the garden. Here is a link to the podcast episode, it is also available anywhere you listen to podcasts! In Defense of Plants episode 263: Earthworm Invaders. In life sometimes the things we believe are good, are not always good for everyone/everything. Remember to keep your mind open to new perspectives because you never know what someone else may be experiencing. For example, earthworms may be great for your garden but they are not for forests!


In the garden, our plants are mainly European natives so the earthworms that are invasive actually thrive in the garden! A lot of the plants we cultivate like to grow with the invasive earthworms because they both originally came from the same origin. There are native earthworms here in Michigan too; they are generally smaller and less aggressive in the soil than the invasive ones, so they take a lot longer to break down the top layer of soil. In a natural forest, the top layer of plant matter on the ground is supposed to be very thick and fluffy, with lots of leaves and pine needles gathering up and making homes for ground living organisms. With the invasive earthworms, that top layer of plant matter is broken down in a matter of a few months instead of slowly over multiple years and it results in a highly compacted soil that is more difficult for native plants to grow in and easier for some invasive plants to grow! Invasive garlic mustard and buckthorn grow with wild abandon in earthworm invaded soils. On top of that, grazing deer eat native trilliums and other native plants that in turn wipes out the understory plants that were holding together the soil and landscape, farther reducing the quality of the soil. Earthworms are also detrimental to the maple syrup industry! Sugar maples thrive in the natural Michigan forest and the compaction of the soil along with the reduced leaf cover, maples get very thirsty and have difficulty getting water! Any organism living under the canopy on the surface of the soil is impacted by the earthworm, salamanders, ground nesting birds, and other important food chain organisms. There is no chemical that kills only invasive earthworms and there is no effective way to remove them from an area without destroying the natural parts that are left. What we can do is reduce our impact on the situation by being aware of what we do! Earthworms can only move so far on their own every year, a patch of them can spread a only a few hundred feet at the most without humans. So it is really important to remember when taking soil or plants from one area that may be invaded, never take it to an area that has no earthworms! You may not see them in the soil so you may have to do some investigating, but you don't want to start a new infection in a place that never had worms! On the bright side, it is all a cycle of life. And the best thing we can do is to be aware and know that we shouldn't feel bad about gardening or using earthworms to our advantage. We should remember there are a few easy things we can do to reduce our overall impact and simply slow the invasion in our forests. Here is a list of action steps you can take to slow the spread of this invasive species! 1. As I said above, don't move plants, soil, mulch or leaves unless you are sure there are no earthworms or cocoons (you'll have to do a little investigation). Learn how to use a dichotomous key (great for identifying all sorts of organisms). Here is a link to the Great Lakes Worm Watch page that give a ton of information on worm ID. 2. If you use worms as bait, don't throw extra worms out into the forest! Throw them away in the trash even if they are dead. 3. If you have a worm composting box (vermicompost) freeze the castings you collect before use to ensure death of worms and their eggs. 4. When driving vehicles in the forest like ATVs, be sure to wash all soil off of the tires before transport because they can carry earthworms and their cocoons. 5. Spread the knowledge about these little forest destroyers!! Below I have linked all the articles and information I used to write this and I encourage all of you to go and check it out.


Great Lakes Worm Watch - stop the spread

Earthworms at the Root of Sugar Maple Decline

The "dirt" about earthworms

Minnesota DNR information

The Effect of Non-native Earthworms on Northern Michigan Soils


Check out these links and remember, don't underestimate the power of a small organism to impact the ecology of our surroundings. That should also remind us of our impact on the ecology of the area. Be mindful and have a happy week :)


Happy growing,

Gabby Waterman


The biggest Sugar Maple I have even seen before

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