How to Deal with Earthworm Castings on Your Lawn

earthworm in grass

If the piles of soil in your yard are roughly the size of a quarter, you might have struck mulch gold. These piles are earthworm castings (also known as worm poo) and significantly benefit your yard. But sometimes, excess worm waste can be too much of a good thing. 

Our guide will show you how to deal with earthworm castings on your lawn and reap the benefits if you choose. 

What are worm castings?

close-up of earthworm castings in grass

As worms wiggle beneath your yard’s surface, they consume soil, microorganisms, and organic matter. The material passes through the worm’s digestive system and exits as waste, also known as worm castings. Worm castings look like small piles of soil and are roughly the size of a quarter. Don’t mistake these piles for molehills, which look like little volcanoes in the yard. 

Worm waste contains essential nutrients like nitrogen, phosphorus, potassium, iron, calcium, and sulfur. The worm’s digestive system creates a coating around the waste, which allows for the gradual release of nutrients similar to slow-release fertilizer. Worm castings also contain soil microbes that improve nutrient availability, decomposition, and disease and pest suppression. 

Worm castings peak in autumn but can pop up in the yard at any time of year. They’re a common maintenance problem in golf courses. However, some people love worm castings so much that they make their own vermicompost bins to break down their kitchen scraps — though it’s worth noting that red wigglers are more suited to this task than your backyard earthworms.

How to deal with earthworm castings

When earthworm castings are ruining your lawn’s curb appeal, the last thing you want to do is spray the yard with non-selective pesticides to eliminate the worms. Killing all the worms in your yard might control the castings, but it will only create more problems for your lawn. Pesticides also can harm other beneficial insects. 

To keep the earthworm castings under control, here’s what you can do: 

Grab the rake

Rake in front of tree in colorful leaves
Peggychoucair | Pixabay

Clear your lawn of earthworm castings by raking or sweeping the soil piles when they’re dry. Collecting them while wet won’t do any good, so don’t perform this task after a rain shower. 

Once you’ve raked or swept up the castings, toss them in your compost bin or garden soil. While you enjoy a clean yard, your plants will enjoy free fertilizer. 

Adjust your watering routine

Overwatering encourages worms to rise to the surface (which is where they’ll leave their castings). 

In other words, you don’t want your lawn’s surface to be consistently moist. That’s why it’s better to water your lawn less often and for long periods than to water too often and for short periods. Watering infrequently and for long periods also encourages a deeper root system and is healthier for your lawn. 

And don’t give your lawn more water than it needs–– most established lawns need only 1 to 1.5 inches of water per week. To determine how long you need to water:

  1. Place empty tuna or cat food cans around your lawn. 
  2. Turn on your sprinkler.
  3. Time how long it takes for the cans to fill up with 1 to 1.5 inches of water. If it takes a different amount of time for different areas, find the average. 

Raise the mowing height

If you want your lawn to reap the benefits of worm castings but don’t like how they look, raise your mowing height. The taller grass will help cover the castings. 

Lower the earthworm population

Sometimes, excessive worm castings are a sign of a high earthworm population. To lower the number of earthworms in your yard, consider making conditions less hospitable (but don’t exterminate them with pesticides). Learn how to control earthworms in the section below. 

How to control earthworms

If your yard is overflowing with worm castings, there are some steps you can take to lower worm activity. Earthworms benefit your lawn’s soil, so you don’t want to eliminate them all –– just enough to minimize the unsightly castings. 

Remove thatch 

illustration explaining thatch on grass
Infographic by Juan Rodriguez

Thatch is the layer of dead and living organic matter that accumulates between the soil surface and the grass blades. Earthworms love to munch on the thatch layer, so you can encourage them to search elsewhere for food by getting rid of their snack. 

How, you ask? By dethatching your lawn with a dethatcher, power rake, or vertical mower. You’ll run your tool of choice all over your lawn to remove the layer, then clean up the debris. If you’d rather not do it yourself, professional dethatching costs around $190 an hour.

Manually remove the earthworms

After a heavy rainstorm, worms will often wiggle to the surface. Pick up the earthworms and toss them in your compost bin, sell them to a local garden center, or use them as fishing bait. 

Introduce a natural enemy

Birds will gladly keep your earthworm problem in check. Invite birds to your yard with bird feeders and birdbaths. 

Chickens also can help control worms, but they’re not always a good option. Why? Because you’ll have to deal with chicken poo on the lawn instead of worm poo. 

Reduce organic matter 

Do you routinely add compost as a top dressing over your lawn? You may be encouraging the worms with these tasty lawn treatments. Minimize the application of organic matter to help ward off earthworms. Removing grass clippings also will restrict organic material on the lawn. 

What are the disadvantages of worm castings?

Worm castings offer significant health benefits for the lawn’s soil, but worm castings have drawbacks when they take over the yard. 

  • A yard with too many worm castings can look unkempt and ruined with a lumpy and uneven feel.
  • Worm castings can make lawn mowing difficult and even dull the mower blades. 
  • Excessive castings in the yard also might signify that your soil has a high number of earthworms. This makes it an attractive hunting ground for moles, gophers, and armadillos, which can easily tear up your lawn. 

What are the benefits of worm castings?

picture of worm cast in compost bin
Lou Wagstaffe | Canva Pro | License

Worm castings aren’t all bad. Many homeowners would be pleased to find worm castings in their yards due to their benefits and uses. 

Benefits of worm castings for the lawn

  • Increased soil fertility: As the soil, microbes, and organic matter pass through the earthworm, the invertebrate’s digestive system adds more microbes and nutrients to its digesting food. As a result, the castings are more nutritious than the surrounding soil. Okay, but what’s the big deal about nutritious soil? The bottom line is that worm castings improve your lawn’s soil health, which ultimately improves the health of your turfgrass. And the healthier your turfgrass, the more beautiful and robust it will be. 
  • Free and eco-friendly fertilizer: Since worm castings act as a natural fertilizer for your lawn, you’ll save money on costly commercial fertilizers and protect the environment from harsh chemicals. 
  • Repaired topsoil: Earthworms that expel their castings on the soil surface help rebuild topsoil, the most fertile layer of soil. The planet is losing topsoil at a rapid rate due to erosion, yet topsoil is necessary for growing crops and grass. 
  • Free and nutrient-rich mulch: Don’t know what to do with the worm castings in your lawn? Rake them up and sprinkle them in your garden. Even your vegetables enjoy a health kick now and then. 

Brownie points: Earthworms offer more than just their castings. Earthworms have many benefits for the lawn, including thatch control and aeration.  

Benefits of worm castings for the garden

When worm castings appear in your yard, why not toss them in your garden as mulch? Your plants will love the added nutrients, and your garden soil will appreciate the health boost. 

  • Beneficial microbes: Earthworm castings have a high concentration of microbes that help repel pests and soil-borne plant diseases. That means your fruits, flowers, and veggies will likely grow healthier, and you can rely less on pesticides. 
  • Nutritional boost: Castings are highly nutritious and provide food for plants, speeding up germination and producing a higher yield. 
  • Slow-release fertilization with no burns: When the manure exits the worm, the worm forms a mucus coating around the manure that allows the nutrients to release into the soil slowly. The worm casting is a ‘slow release’ fertilizer that won’t burn your plants like some commercial fertilizers can. 
  • Improved moisture retention: Worm castings help retain moisture in the soil, which can prove helpful for plants that can’t tolerate dry soils. 

FAQs about how to deal with earthworm castings on your lawn

What kills earthworms in lawns?

Certain pesticides intended for other pests, such as carbaryl and imidacloprid, are toxic to earthworms in your lawn

Lawn care and gardening experts don’t recommend killing earthworms. While it may be tempting to treat earthworms like any other pest, they are crucial to the environment and your lawn’s health. The mere presence of earthworms is a sign your soil is healthy. Pesticides could threaten that health.

Rather than a scorched earth approach that harms earthworms and other beneficial creatures, focus on integrated pest management. Integrated pest management prioritizes prevention and cultural practices, with pesticides as a last resort. This strategy has better long-term success since it solves the root of the problem rather than attacking only the symptoms. 

Why are worms coming out of my lawn?

Worms come out of the lawn for food, to mate, or when it rains. Scientists still debate why worms surface in the rain, but the most common theory is that it’s easier and faster for them to move above ground when it’s wet out. 

What eats earthworms?

Besides birds, many creatures hunt earthworms for food, such as:

  • Badgers
  • Cluster flies
  • Devil’s coach horse beetles
  • Foxes
  • Moles

However, it’s not wise to encourage all earthworm predators. Some will dig up your yard in search of food, which means you’re trading one unsightly problem for another.

Should I put earthworms in my yard?

Though they provide many benefits, putting earthworms in your yard is unnecessary. This may sound confusing after we’ve explained all their benefits, but hear us out. 

Earthworms aren’t a necessity for a healthy lawn or garden. They’ll likely show up in healthy soil, but they aren’t a cure-all solution for your lawn care or gardening woes. You’ll need a combination of several beneficial lawn treatments to keep your grass healthy. 

An excess amount of earthworms also can harm the local ecosystem, especially since many species aren’t native to North America. It’s best to attract and encourage the existing population rather than introduce them where they didn’t exist before.

What other pests cause mounds of soil?

Besides earthworms, mounds of soil may be left by several digging creatures, such as:

  • Armadillos
  • Bobcats
  • Chipmunks
  • Coyotes
  • Deer
  • Foxes
  • Gophers
  • Mice
  • Mole crickets
  • Moles
  • Rabbits
  • Raccoons
  • Rats
  • Skunks
  • Snakes
  • Squirrels

To stop animals from digging, follow these methods:

  • Eliminate food sources, water, and shelter
  • Use physical barriers like above or below-ground fencing
  • Apply homemade or commercial chemical deterrents
  • Use lights, scents, sounds, or sprinklers as scare tactics
  • Set traps (following any legal guidelines)

Find a balance and hire a pro

Is your lawn suffering from worm poo blemishes, but you don’t want to eradicate the presence of earthworms? Hiring a local lawn care professional can help you strike a balance. 

Skilled in their craft, a lawn care expert can get to the root of your worm casting problem without eliminating your helpful worm population. They can keep your lawn healthy and neat without sacrificing the benefits earthworms provide. From weekly mowings to regular maintenance, leave your lawn in good hands. 

Main Photo Credit: sarahharding | Pixabay

Jane Purnell

Jane Purnell is an artist, writer, and nature lover. She enjoys teaching readers about the importance of eco-friendly lawn care, integrated pest management, biodiversity, and sustainable landscaping.