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Earthworms in your lawn – nature’s aerators

The appearance of worm casts on your lawn is perfectly normal and, in fact, the presence of earthworms is a sign of a healthy lawn; one that is working well with nature. 

Worm activity and its impact on lawns is usually experienced most during wetter conditions as soils are more easily travelled when soft. Higher water tables experienced in wetter seasons also drive the worms up through the soil profile. As a result, worms are often most active in autumn and through warmer winters.

For many years, gardeners and turf professionals have had chemical products that eradicate worms, however, legislation has removed these products from the market. In line with Rolawn ethics, we want to encourage understanding about how to work with worms, how they benefit our environment and how important they are to our ecosystem. 

Identifying worms in grass

You can see when earthworms are present because their activity produces small mounds of fresh soil on the surface of the lawn, wormcasts. If the earth is particularly wet then you may also notice earthworm holes, approximately 6mm in diameter, across the lawn.

You may even see the worms themselves. Living in the upper 300mm of the soil, they are generally brown to reddish-brown in colour and can vary from 6-200mm long.

Benefits of earthworms and worm castings

Earthworms and worm castings are a natural method of cultivating and improving soil. They 'eat' soil and thatch in the turf and help to break down other organic material on the surface of the grass. These materials are mixed and digested by the worm then excreted as a worm cast. In most cases this happens in the soil, but during the night hours, when the lawn is cool and wet, the worms are active on the surface. In the morning, the evidence of their activity is seen in small mounds scattered on the lawn.

Underneath the lawn, earthworm activity helps to create space for the movement of water, air and nutrients – the key elements needed for healthy grass plants. 

What to do about earthworms and their castings

Rather than looking at how to get rid of worms in a lawn or how to stop worm casts, use them to your advantage by allowing them to aerate and condition the lawn. You may find that the appearance of your lawn isn’t as neat and ‘manicured’ as it is during the active growing season but the work being done by nature will help to reinvigorate the lawn when it is needed.

The following suggestions can help with managing earthworms: 

  1. Let the castings dry and brush them back into the turf, especially just before mowing.
  2. Maintain a year-round maintenance programme that includes regular mowing, fertilisation and aeration.
  3. Collect grass clippings.
  4. Don't be tempted to use a garden hose to wash away the castings, this may actually force more worms to the surface because they cannot breathe in wet soil.

Top dressing your lawn to repair the effects of worms

Leaving the worms to do their job can, over time, create a slightly uneven lawn but this is manageable. Without a doubt, the best solution is one which forms part of a regular, routine lawn maintenance programme – top dressing. Adding an application of lawn topdressing helps to level out the dips, improving the look of your lawn as well as assisting the health of the grass plants and helping prevent the build up of thatch.

Naturally produced turf may contain worms

New turf that comes from a responsible supplier will have been grown with the environment in mind. If you lay new turf which contains earthworms, this means that the turf has been produced in line with the regulations preventing the use of chemical controls. 

For more techniques to help you maintain a healthy lawn, explore our other lawn aftercare advice.