Have you ever wondered what the small heaps of muddy soil are that appear on your lawn at this time of year? They are worm casts – waste products from the guts of earthworms that live in soil all year round. Earthworms have enormous benefits for the health of turf – find out what these benefits are and how to deal with worm casts, with advice from Paynes Turf.
Earthworms are great for lawns in terms of soil structure and the recycling of nutrients into the soil. Their burrowing also greatly improves aeration in the soil and boosts drainage. Ultimately, worm casts are a sign of the presence of earthworms in your soil, which is an excellent indication of healthy turf.
How are worm casts formed?
The worms feed on organic matter, such as dead plant material, and while doing so ingest some of the soil. The worms would normally excrete their waste underground, however if the soil is very wet they will deposit the excrement above ground. Some species of earthworm favour the surface of the turf to deposit the excrement. This is how the casts are formed. The deposits are muddy in appearance and have a wet consistency – this can sometimes spoil the look of a perfectly manicured lawn, particularly when the casts get trodden on and are smeared across the surface of the lawn.
Why do I have worm casts on my lawn?
Earthworms come up to the surface of the lawn to feed and breathe if the soil below is too wet – this is why you will usually find worm casts in the mornings, especially if the turf is soggy. It’s important to keep earthworms in your lawn for the health and soil structure benefits they bring, so the best remedy is to sort out any drainage issues your lawn has. Aerate your lawn regularly, and if necessary, install a drainage system to allow water to drain away faster.
If you have a significant amount of worm casts, it may be worth reducing the amount of matter they have to feed on – don’t leave the clippings on the lawn after mowing, and remove fallen leaves quickly.
How to remove worm casts
Try not to mow or walk on the lawn while the casts dry out. To remove worm casts, simply leave them to dry before sweeping them back into the turf.
Unfortunately, it’s possible for worm casts to contain weed seeds, because the earthworms ingest grass and other plant material which contains seeds. When worms deposit casts on the surface of the turf, it can create an area of bare turf which, when combined with the seeds in the worm cast, could encourage moss and weeds to grow.