Problems with Worms & Worm Casts in the Lawn

Worms benefit the lawn by increasing organic breakdown and improving aeration and fertility however they do cause problems with their spiral casts

There are about 27 species of worms in the UK but only three create worm casts at the surface of your lawn. These casts are waste soil that has passed through the worm as it moves around. This benefits the soil and lawn by increasing organic breakdown, improving aeration and fertility. They also ‘plug’ their holes with leaves and twigs which can create an unusual landscape with upright leaves sticking up all over the lawn. The point being, a lawn with worms is much healthier and will have fewer problems than a lawn without worms.

The downside, there always is one, is that the cast creates bumps in the turf which, when flattened by the mower are unsightly and a great place for weed seeds to settle and germinate. In fine sports turf they are a major problem but in anything other than an ornamental lawn they should be able to be lived with whilst requiring only minor management.

Quick Guide to Living with Earthworms

Worms are great for the lawn, soil and for attracting wildlife. If you can live with the mess but want to reduce it a little then try these:

  • Remove grass clippings whenever you mow
  • Do not use organic fertilisers or composts on your lawn
  • Try to keep off the lawn during the winter months
  • Clear autumn leaves immediately as this attracts worms
  • Avoid excessive or unnecessary watering of the lawn in summer
  • Keep the late autumn/winter mowing height on the high side
  • Brushing worm casts (image) to disperse them helps but only works on dry casts

Quick Guide to Worm Management

Worm killers are now banned as far as you are concerned. This means managing the situation is your only option. Start with all the points above plus:

  • Collect worms by applying a dilute mustard solution. This brings the worms to the surface for hand picking. Great if you’re a fisherman or have Koi!
  • Alternatively, if you regularly use an acidifier such as Ferrous Sulphate a.k.a. Soluble Iron on the lawn then this will temporarily make the conditions less inviting for the worms. This can be a slow process and best started well before casts appear. There are added benefits to this as the moss doesn’t like the ferrous sulphate and the grass does. You’ll get a greener lawn and fewer muddy casts eventually!