Worm bumps or casts are small piles of earth caused by the activity of earthworms. They are deposits of earth which has passed through the earthworm's gut and from which nutrients have been removed. The bump or cast is created as the soil is pushed out of the worm's rear end.

The presence of eartrhworms (and their bumps) usually indicates a rich soil, full of nutrients and earthworms are themselves valuable to the garden because their tunnels provide aeration for the soil and also help assist draiange. They help break up compacted soil and take organic matter deeper within the topsoil to enrich and improve the soil's structure.

So earthworms can be beneficial. However, their mounds, whilst of little consequence in beds or other parts of the garden, can be a problem in a lawn if they are visible. Not only that but they may provide the perfect environment for weed seeds to germinate and they can also bring dormant seeds to the surface where they will germinate so weeds can, withth epresence of worm bumps, be able to become established in otherwise pristine lawns.

There are several ways to remove the worm bumps.
First and probably the best method, is to scatter the bumps using a broom or besom. This scatters the earth evenly across the lawn so keeps the earth within the lawn area yet prevents weeds from germinating.

The second way is to kick the mound with your foot to scatter the earth. This can cause damage to the sod and grass plants surrounding the mounds and should only be used where a besom is not readily available.

You can water out the bumps by watering the piles of earth until the soil floats evenly away and so the mound is smoothed.

You can also treat your lawn to get rid of the worms causing the casts or bumps in the first place. This is usually not necessary unless you have to retain a fine lawn with a deep, even green surface such as those needed for bowling greens or golf tee areas. Soak the area with a proprietary worm killer available from garden centres.

Killing earthworms should not be undertaken lightly due to the enormous benefits these creatures bring to the soil. Earthworms and other beneficial organisms promote the health of our soils and their removal means a great part of the overall soil health can be lost. If you can, it is best to live with the bumps and deal with them as and when they occur. You may find you get relatively few bumps appearing one year and a flurry of them the next but remember, the worms will be working below ground to provide drainage and air to your precious grass plants. They turn organic material into soluble nutrients which the plants can absorb so getting rid of them also robs your plants of a precious source of nutirents.

It is better to live with a few worm bumps than kill the worms.

Learn more about this author, Sammy Stein.
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