How Earthworms Help Your Lawn, Grass and Soil

Earthworms - how they help your lawn

The worms crawl in …

The worms crawl out …

The worms play … a surprisingly valuable role in the health and fertility of your lawn!

Many gardeners understand the benefits of earthworms in their garden, but homeowners are less aware of how these wriggly guys help their grass, too.

Earthworms are a key player in vermicomposting, a variation of traditional composting where microorganisms and worms break down organic materials into worm-castings or vermicast, a nutrient-rich organic fertilizer and soil amendment. In other words, earthworms are just as good for your lawn as for your garden. When found in your lawn they perform the same functions for the turf instead of in a dedicated compost pile. They add organic material and the tunnels they dig create air spaces necessary in a healthy soil structure.

All About Earthworms

While most of us learn about these slimy beings as young children, earthworms are unique, interesting creatures.

  • Earthworms are tube-shaped worms with ringlike segments on their bodies.
  • These segments are covered in small bristles called setae that allow them to move and borrow.
  • They have no internal skeleton or exoskeleton.
  • Respiration occurs through their skin, breathing in oxygen and giving off carbon dioxide.
  • Each individual earthworm is a hermaphrodite, carrying both male and female sex organs.
  • During mating each earthworm in the pair uses both sets of sex organs, fertilizing the eggs of both mates.
  • Endogeic species of earthworms commonly live in soil; epigeic species live in moist leaf litter on the forest floor.
  • Their diet consists of decomposing organic matter commonly known as humus.
  • Native United States species died out about 10,000 years ago; most U.S. earthworms are non-native, invasive species from Europe.
  • Nightcrawlers (Lumbricus terrestris) are the most common earthworm species found in lawns. They are a brownish red in color and grow up to a few inches long.

How Do Earthworms Help?

Well over 100 years ago, Charles Darwin began investigating earthworms to discover how important they are in soil fertility and agriculture. Lately, homeowners and gardeners have taken a keen interest in their importance in lawns and gardens.

Earthworm activity is an excellent gauge of overall soil health and their populations have a direct relationship to plant growth and productivity. They help in lawns by improving the soil structure, breaking down thatch, and releasing plant usable nutrients as they break down organic matter. This is accomplished by both the act of burrowing through the soil and consuming partly decomposed organic matter.

As they burrow through the soil, they create tunnels that improve water infiltration and aeration, improving the overall soil structure and loosening the soil for better root growth. Their constant up and down movement through the soil profile also results in a tilling action of sorts that doesn’t disturb the soil surface and grass. This “tiling” continuously brings “fresh” soil from deeper depths up to where the plants are actively growing.

Earthworms’ tunnels help break up compacted soil, leaving room for air to flow and roots to flourish.

While living in soil, earthworms feed on two different components. They do not actually eat the turfgrass, but instead the thatch layer just below, constantly working to decompose and reduce the thatch. As they burrow they also swallow soil, feeding on the microorganisms and partially broken down organic material in the soil.

Earthworms excrete their waste following digestion. Earthworm casts left behind are full of nutrients that replenish the soil. Enzymatic reactions within their guts change the forms of nitrogen and phosphorus in the soil they ingest to soluble ones available for plant uptake.

Castings can interfere with the straight roll of a golf ball, so the U.S. Golf Association considers the presence of excessive earthworms to be a “serious and widespread” problem for golf course managers. But for the rest of us, bring ’em on! Here’s how.

How to Encourage Earthworms in Your Lawn

According to Uncle Jim’s Wormfarm, healthy soil contains five to 10 earthworms per square foot of surface area. While earthworms won’t move a long distance to relocate there are ways to encourage them to stick around if they are there, increasing your earthworms naturally.

  • Maintain a healthy lawn by keeping it weed free, and the pest population low.
  • Water the grass regularly to encourage a strong root system, while not overwatering.
  • Provide a constant supply of organic material for your lawn earthworms to feed on. Some homeowners sprinkle cornmeal on the soil surface to encourage earthworm populations.
  • Regularly dethatch the lawn to prevent a thick barrier within the top layer of soil. Earthworms need access to the soil surface and condensed thatch prevents that.
  • Do not use pesticides that can harm earthworm populations.

Where to Buy Earthworms

If your lawn is lacking in wiggly helpers you can always purchase earthworms or earthworm eggs to add, and then use the tips above to encourage them to stay.

Pro tip: For lawns, it’s better to buy earthworm eggs than adult earthworms. That’s opposite the advice for garden soil, where adults are preferred. Adult earthworms may not be able to tunnel into the turf’s soil quickly enough to stay alive. They can dry out too much on the soil surface and die. Egg cocoons are placed a few inches below the soil surface and can hatch anywhere up to twenty worms.

Locally you can find earthworms at lawn and garden centers, and anywhere fishing bait is available for sale.

Online retailers include:

Once you put earthworms in your lawn and convince them to stay, congratulations! To any knowing gardener — or lawn owner — their presence is a sure sign that your soil is in good shape and ready to host a happy, healthy lawn.

Amanda Shiffler

Amanda Shiffler

Most comfortable with soil under her fingernails, Amanda has an enthusiasm for gardening, agriculture, and all things plant-related. With a master's degree in agriculture and more than a decade of experience gardening and tending to her lawn, she combines her plant knowledge and knack for writing to share what she knows and loves.