Earth worms in lawns

Author: Stefan Palm   Date Posted: 7 July 2021 

During Winter, it’s not uncommon to see mounds of dirt appearing on top of your lawn. This may be an indicator that you have earth worm activity in your soil.

Most gardeners will know that worms are good for the soil for a whole bunch of reasons (which I’ll get to later) but they can leave behind their casts on the surface when conditions are wet, typically between May and September.

Worm Castings

Earthworms live in the top 30cm of the soil and come to the surface to eat, breath, hatch and breed and of course this is when they deposit their casts, generally during the night. While this can be messy and unsightly, worms bring many benefits for your lawn – lawns with worms are better off than lawns without them!


As they burrow through the soil under your lawn, they naturally aerate it, introducing air which lawns love.  In their burrowing, they eat soil, organic material, and lawn thatch breaking it down as they digest it. This has a two-fold effect. Firstly, in doing this they remove thatch from the lawn which is a good form of natural pruning and secondly, they produce castings. When the soil is wet, they come to the surface and deposit these small piles of soil or castings which of course is the broken down thatch, organic material and soil. The worms do a wonderful job of breaking these elements down, releasing their nutrients which is a great benefit for your lawn.  

What not to do:

Hopefully I’ve convinced you that they should be a welcome guest in any lawn so don’t try and kill them! Given that they come to the surface more readily when its wet, don’t use a hose to water the castings into the soil. By doing this, there is a fair chance that you’ll encourage them to come up more frequently.

What to do:

If you’re getting an excessive amount of casting piles on the surface, then consider the following:

  • Improve the drainage of the soil so that it's not waterlogged or slow to drain.
  • Make sure that the lawn isn’t being excessively irrigated during the Winter
  • Allow the castings to dry out then brush them off
  • Regularly scarify your lawn and pick up clippings and leaves to reduce food sources.

Be assured that earth worms will never damage your lawn or cause dead spots.  They are a sign that you have a healthy soil and will do a mighty job of helping it to stay healthy. At worst, they can cause some mess which may need tidying up but in my opinion, that’s a small price to pay.  

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