History

• Earthworms found in the northern U.S. are not native to the country, according to Wildlife Gardeners. This is due to the fact that the last Ice Age killed all remaining native earthworms in America. But they made their way to the U.S. during the end of the 1800s and the early 1900s via the soils and plants brought in from Europe and Asia, according to the Minnesota Department of Natural Resources.
  
  

Significance

• Fortunately, earthworms don't travel very quickly. In fact, their movement (and potential problems they can create to lawns) is limited to a 1/2-mile radius for every 100 years of life, according to the Minnesota Department of Natural Resources. So if Americans stop introducing earthworms into their communities, lawn problems due to earthworms will at least stop spreading as quickly.
  
  

Geography

• Lawn problems caused by earthworms are sometimes influenced by the geographical location of the earthworm. For example, earthworms found in the hardwood forest-type areas including upstate New York, have the ability to impact native plants through their ingestion of tree leaves. According to the website Wildlife Gardeners, when earthworms eat tree leaves in this part of the country they sap the native plants of nutrients the leaf would have provided to them, as well as reducing potential warmth from leaf ground cover. In addition, the soil is affected, since earthworms make it denser, resulting in soil compaction. This causes surface runoff, and thus erosion.
  
  

Considerations

• While earthworms can leave castings (refuse) on any lawn type regardless of their geographical location, this debris left behind is more problematic on some lawns than others. Golf putting greens and courses feel the impact of earthworm castings and burrows more significantly than the average lawn. These castings impact uniformity and appearance, as well as players' ability to play effectively, on golf courses, according to the United States Golf Association.
  
  

Warning

• Another problem that can result from having earthworms on your lawn is that they draw moles to them. Moles feed on earthworms. And having moles chasing after (and eating), earthworms in your lawn can also affect its appearance. And it can impact the roots of your grass and other plants too, since moles often tunnel deep in search of food.