Worm Casts All Over The Lawn

What's happening?

The RHS describes worm casts as small heaps of muddy soil ejected from the digestive tract of some earthworm species, mainly Aporrectodea and Lumbricus, which live in permanent vertical burrows. Freshly deposited casts often have a coiled appearance and a fine muddy nature that tells them apart from soil brought up by ants, mining bees and moles. Worm casts are considered by some gardeners to be a nuisance on fine, low-cut turf and gravel paths, but the RHS says the action of worms in the garden is beneficial and casting worms should be tolerated wherever possible. Deposition tends to peak in autumn and early spring, and in mild winters can continue throughout.

What usually causes it?

• Earthworm species that live in permanent burrows and deposit casts on the surface
• Autumn and early spring, when the RHS says casting tends to peak
• A fine, low-cut lawn or gravel path, where casts are most noticeable
• Mild, damp winters, when casting can continue throughout
• Soil that suits earthworms, since the RHS says they are much less abundant in acidic soils

Is it dangerous?

No. The RHS says earthworm activity improves soil structure and recycles nutrients. Casts are noticed mainly on fine, low-cut lawns and gravel paths.

Can I fix it myself?

Wait until the casts are dry, then brush them off or rake them: the RHS says to use a wire rake with the teeth facing upwards and move it from side to side to break up and disperse the casts, and to remove casts from paths with a trowel. It notes this is only possible when the casts are dry, and that there are often few dry days in autumn to spring. The RHS lists treatments that can be applied, but says casting worms should be tolerated wherever possible.

When should you call a gardener?

Call a gardener for regular raking and brushing of a fine lawn through autumn and spring, or if you want a lawn care programme. There is no need to call anyone for the worms themselves.

What will the gardener actually do?

• Brush or rake dry casts to disperse them, as the RHS describes
• Check the lawn for moss, weeds or bare patches that casts have encouraged
• Advise on mowing height and routine for the lawn

Who fixes this

• Lawn care

Questions people ask

Sources & References

1. RHS: worm casts in lawns
2. RHS: earthworms