“Worms have played a more important part in the history of the world than most persons would at first suppose.” - Charles Darwin
Unless you are an avid gardener, you most likely aren’t even aware of what is going on in the soil, preferring only to notice how well the grass is doing or what flower is blooming, and that is just fine! But there, one soil-dwelling organism is dutifully toiling away; burrowing and recycling organic matter right under your feet!
Many of us were raised to respect and appreciate the unsung hard work of these wriggling little slimy beings, grateful to them for enriching the soil. Always saving one when it gets caught on the sidewalk after a rain.
There could be up to 200 Earthworms per square meter of topsoil, burrowing and eating dead leaves and roots. Happily doing their thing oblivious to the rigors of our modern world. These invertebrates live anywhere in the world where there is ample food, moisture, oxygen, and favorable temperatures.
Earthworms are essentially one long digestive system, an outer muscular body wall surrounding a digestive tract that begins with the mouth in the first segment.
They are usually considered beneficial organisms, vital to soil health by transporting nutrients and minerals to the surface by way of their waste - called castings.
The slimy secretion on the outside of an Earthworm contains nitrogen, which is an important nutrient for plants and helps hold soil particles together. Earthworm mucus helps them glide through the soil and it helps them breathe through their skin. This is why they, and their environment, must be moist at all times.
More Earthworm Facts
There are over 100 species of native Earthworms in the Southeastern U.S. and the Pacific Northwest. Oddly enough - nearly every Earthworm in the Northern U.S. actually came from somewhere else!
Native Earthworms north of Pennsylvania all but disappeared more than 10,000 years ago, when ice age glaciers wiped them out.
The non-native Earthworms first arrived with soil and plants brought from Europe, most likely in ships traveling to North America which used rocks and soil as ballast, which was then dumped on shore as early as the 1600s. European plants likely had worms or their cocoons in the soil too.
Today, the use of Earthworms as fishing bait has spread them further! All common bait worms are non-native species, including those sold as Night Crawlers, Canadian Crawlers, Leaf worms, or Angle worms. At least fifteen non-native species have been introduced so far.
How can something with no eyes, limbs, ears, or an obvious brain be smart you ask?
Even without eyes, they can sense light and move away from it, becoming paralyzed if exposed to as little as 1 hour of light.
Charles Darwin spent 39 years studying Earthworms, suspecting they had basic intelligence. After watching them choose leaves by their shape, he learned that Earthworms pulled food into their burrows by the ends most likely to fit.
We used to think Earthworms raced onto the pavement during rainstorms to avoid drowning but now theories suggest that they’re actually confusing the sound of raindrops with moles digging through the soil. They can feel sound vibrations and avoid underground predators such as moles, other mammals, and snakes. Other experiments show they can learn to navigate mazes and get faster each time. If threatened, Earthworms ‘herd’ together, and communicate by touch.
This makes me feel even worse whenever I jab one on a fishing hook!
While most of us know Earthworms are beneficial creatures that work away at enriching the soil, there is a realization that they may not be without their faults too.
Where they are native and when in the vegetable garden setting, aerating and loosening soil, Earthworms are very beneficial! They create and enrich the soil, loosen soil compaction, and their tunnels create "macro-pores" that help water move through the soil. They also help incorporate organic matter and minerals into the soil to make more nutrients available to plants.
As Earthworms chew and churn the soil, researchers suspect they have an impact on its ability to store that carbon, easing many of our climate change concerns. As organic material decays, it releases CO2 into the atmosphere, and Earthworms both help speed up the process as they break down leaf litter and wood, causing microbes to release more CO2 than normal, they also excrete soil as casts which take longer to break down, making it so the carbon stored there stays in the ground longer.
Because Earthworms weren’t around since the ice age, Northern hardwood forests developed in their absence by relying on the microbial and bacterial decomposition of the leaf litter - which is slow and steady. Creating a spongy layer of organic "duff", which is a deep, natural environment for native woodland wildflowers and understory shrubs.
Earthworms moving in from other parts of the world, or up from the Southern US and South America, break down leaf litter too fast - changing forest soils and robbing plants of organic nutrients. Reducing the variety of understory wildflowers and shrubs and inhibiting tree seedling growth. There is also less duff soil habitat for ground-dwelling animals. This loss of duff is also increasing soil erosion. These same issues are arising in home landscapes and agriculture as well.
So are they good or are they bad? It’s up to you and where you live, but these curious little (and not so little) ground-dwelling invertebrates are here to stay! So we might as well embrace them for the good they can do when in the right location.
We’d love to hear your thoughts on these unique creatures! So join us on the Nature Hills YouTube, our #ProPlantTips Garden Blog, or on one of our many social media sites to hear your thoughts!