Earthworms in the lawn: pests with benefits

The presence of earthworms – a term that refers to any of the legless, tubular, segmented worms that live in the ground – in the lawn or garden of your home is an indicator of healthy soil with a high percentage of organic matter. In most cases, there is no need to worry about worms in your soil. In fact, it is much more worrying if your soil does not contain worms, as this suggests a fairly sterile soil that lacks organic matter.

An earthworm’s job

Most of the time, worms are completely invisible, condition the soil and live their lives deep in the root zone. However, in spring, autumn, or other periods of extreme humidity, earthworms tend to migrate to the surface and theirs Castings on the lawn.Worm litter is small mounds or bumps on the lawn that are basically worm droppings, but very nutritious excrement. These excretions are nutrient-rich remnants of digested plant matter and soil that the worms have passed through – a material that is extremely useful for the lawn.

Earthworms also help break down straw, increase decomposition, and create usable nitrogen in the soil. Finally, the movement of the worms through the soil profile acts as natural ventilation, helping to move air and water from the surface through the root zone.

Earthworms and their casts are very good for the garden and lawn on almost all levels.However, homeowners who prefer a smooth lawn with a pool table sometimes torment themselves over the signs earthworms leave on their lawn.

What is the problem?

Excessive earthworm casts on lawn can be a problem for people in many parts of North America who find an imperfect lawn offensive. The biggest criticism of worm castings is their unsightliness. The little mound of nutrient-rich excrement forms a dark patch the size of a quarter on the lawn. Multiplied by the potential number of worms, this can seriously degrade the aesthetics of a lawn.

A weak, thin lawn that is mowed low looks worse when there are plenty of worm debris. Over time, an abundance of casts on a lawn creates a bumpy surface that leads to scalping when mowed. They can even pose a trip hazard.

Finally, an excessive population of earthworms can also attract secondary pests such as moles, which primarily feed on worms, maggots, and other subterranean creatures.

Dealing with castings

The benefits that worms bring to the soil outweigh the relatively minor inconvenience associated with handling their casts. However, there are some practical and environmentally friendly ways to deal with worm debris on a lawn:

  • Rake or sweep the castings over the lawn when they are dry. This will spread a natural fertilizer over the lawn and break up the unsightly clumps. In the fall, mow the lawn with a power rake to prevent uneven lawns from forming.
  • Don’t overwater. Earthworms stay near the surface when it’s constantly humid, but they will go deeper in search of moisture when the top inches of the soil are drier.
  • Mow high and keep the lawn healthy to hide the debris and minimize unsightliness.
  • Use a roller to push the castings down. However, over time, the bumps still appear and can lead to compaction of the soil.

Lawns that have become uneven and bumpy from years of casting build-up may need to be restored or renovated depending on the severity.Top dressing and overseeding make for a moderately bumpy lawn. In more severe cases, ventilation and rolling may be required to achieve smoothness.


There are currently no pesticides labeled for earthworm control, although some insecticides and fungicides are toxic to them. The use of pesticides “off-label” and contrary to the instructions on the label is illegal, dangerous and is not recommended.

Earthworms in forests

In natural forest areas, for example, earthworms consume the organically-rich leaf material that covers the forest floor and supplies many trees and plants with important nutrients. While the presence of earthworms in an urban or suburban lawn and garden is a good sign, in wilderness forests they are not necessarily a good sign.

Never release worms that are used for bait fishing in wooded areas and carefully examine the soil when transplanting garden plants into the landscape around a cabin or cottage in the woods. This is one area where you want to avoid earthworms.