Pros and Cons of Earthworms in Your Yard

close-up of an earthworm

Earthworms provide your lawn with natural fertilizer and other benefits. But sometimes, too many earthworms in the soil can mimic a pest problem. Should you remove the worms or leave them be? The following pros and cons of earthworms in your yard can help you weigh your decision. 

Hint: You’ll probably decide to keep the earthworms (or even encourage them). Earthworm infestations won’t harm your grass (unlike grubs), and the pros typically outweigh the cons. But if you do decide to solve your lawn’s earthworm problem, we’ll show you how to control them. 

Benefits of earthworms in your yard

Earthworms are more than just fish bait –– they play an essential role in your lawn’s health. As they chow down on your lawn’s soil and decompose its organic matter, they benefit your lawn in several ways.

Aristotle called earthworms the “intestines of the earth,” and for a good reason: 

✓ Improved soil health

Earthworms increase soil fertility with their worm castings (aka worm poop). 

Here’s how: Earthworms consume soil, organic matter, and microbes, and as this material passes through their digestive system, it becomes concentrated with more nutrients and microbes. As a result, the casting is more nutritious than the surrounding soil. 

OK, but how does increased soil fertility help your lawn? Think of it this way: 

Just like you need vitamins and minerals to grow strong and healthy, so does your grass. Your grass gets its nutrients from the soil. Fertile soil has plenty of nutrients for your grass, including potassium, nitrogen, and phosphorus, whereas sterile soil won’t support your grass very well. 

The more fertile your soil, the healthier your lawn is likely to be. And the healthier your lawn, the less vulnerable it will be to weeds, pests, and disease. 

Worms also add nutrients to the soil when they die –– their bodies decompose and add nitrogen to the soil. 

✓ Decomposed thatch

illustration explaining thatch on grass

Thatch is the layer of dead and living organic material accumulating between the soil surface and grass blades. Earthworms like to snack on organic matter, which means they love to snack on thatch. 

A thin layer of thatch is good for the lawn, but a thick thatch layer can be troublesome. A thatch layer that’s one-half inch thick or more can turn into a breeding ground for pests and disease. It can also prevent water and fertilizer from accessing the soil. 

✓ Improved soil structure

Earthworms help loosen compact soil by creating tunnels as they wiggle about and eat, encouraging the movement of water, nutrients, and oxygen. Your turfgrass will struggle to grow if it can’t drink, eat, or breathe, so it’s always helpful to have these natural aerators in your lawn. 

✓ Repaired topsoil

Earthworms help repair topsoil by leaving their nutrient-rich castings on the soil’s surface. Topsoil is the earth’s upper, outermost layer of soil, and its high fertility is necessary for crop and plant growth. 

Yet, due to the erosion, the planet is losing its topsoil at a rapid rate. Homeowners can combat erosion and protect topsoil in various ways, including encouraging earthworm activity in the lawn and garden. 

✓ Deeper roots

As earthworms dig their tunnels, they make space for plant roots to grow deeper into the soil. The deeper your lawn’s root system, the healthier and stronger its turf will be. 

✓ Free mulch

Think of earthworm castings in your yard as free mulch for your garden. The number of earthworm castings in your lawn (which look like smalls piles of soil) depends on the yard’s earthworm population size and how often they rise to the surface

When the castings are dry, rake them up and toss them in your garden. The castings add nutrients and plant food to the garden soil, and their high concentration of microbes can help ward off pests and diseases. (You can also toss them in your compost pile). 

How to encourage earthworms in your yard

If the benefits of earthworms sound like a good deal to you, there are many ways you can increase their activity in your yard. Whether you want to maintain an existing earthworm population or encourage new earthworms to move in, the following tips and tricks can make your yard desirable to earthworms: 

  • Amend your soil so that the pH is between 6.0 and 7.0 (this is also the optimal pH for growing grass). 
  • Give the worms plenty of organic matter to chow down on. Sprinkling compost across the lawn as a topdressing is a great way to add more organic matter.
  • Aerate the soil. Worms won’t find your yard too inviting if its soil is compact. Why? Because worms need oxygen, and compact soil prevents the movement of oxygen. Loosen the soil with an aerator so that worms have better access to air as they work. 
  • Keep your lawn watered and the soil moist. Earthworms don’t like dry conditions. 
  • Reduce your use of pesticides. Pesticides can harm worms and negatively affect their reproduction. Instead, practice a good lawn care routine that keeps the pests and weeds at bay. 
  • Avoid tilling the soil; otherwise, you might kill the earthworms. 

Disadvantages of earthworms in your yard

Earthworms are a great help in the yard and garden, but sometimes, the presence of earthworms may prove irksome when their population is high. Too many earthworms might lower your lawn’s curb appeal and invite critters, like moles and other wildlife.   

✗ Unsightly castings

Finding a few castings in the yard is normal. But sometimes, castings can overtake the lawn, especially when many worms live in the soil. For some homeowners, these unsightly castings can be a dealbreaker. 

✗ Uninvited wildlife

When your soil is overflowing with earthworms, the yard may attract hungry animals, like moles, gophers, and armadillos. These pests can tear up your lawn in search of food, destroying its curb appeal and your hard work.

How to control earthworms in your yard

Had enough with returning moles and excessive worm castings? Depending on your tolerance level, sometimes the disadvantages of too many earthworms outweigh the benefits. 

The key to earthworm control isn’t to exterminate the entire worm population. You still want your lawn to reap the benefits of these decomposers. Here are some ways you can lower the number of earthworms in your yard without wiping them out completely: 

  • Adjust your watering routine. If earthworms are rising to the yard’s surface and leaving behind their castings, it might mean you’re overwatering. Most established lawns need only 1 to 1.5 inches of water per week. 
  • Remove thatch with a dethatcher. Remember, earthworms love to snack on thatch. Removing thatch from the lawn can help eliminate one of their food sources. 
  • Manually remove the worms. After a heavy rainstorm, worms will wiggle their way to the surface. Grab the earthworms and sell them to a local garden center, use them as fishing bait, or toss them in your compost bin to begin vermicomposting
  • Introduce a natural enemy. Birds will gladly gulp down your lawn’s earthworms. Attract birds to the yard with a bird feeder. 
  • Reduce the use of organic matter as a soil amendment, such as compost topdressing. Earthworms love organic matter, and removing this food source can help keep their numbers under control. 
  • Never use pesticides to control an earthworm infestation. Doing so could exterminate all the worms in the yard and harm the ecosystem. 

When to hire a pro

Worms might be a big help in the lawn, but they can’t carry the whole thing on their backs. Give these hard workers some assistance by hiring a local lawn care professional. From mowing the lawn to aerating the soil, a lawn care pro can maintain your lawn’s beauty while also encouraging a healthy earthworm population. 

Main Photo Credit: Katja Schulz | Flickr | CC BY 2.0

Jane Purnell

Jane Purnell is a freelance writer and actor in New York City. She earned her B.A. from the University of Virginia and enjoys a warm cup of French press coffee.