How to Get Rid of Worm Casts on Your Lawn

Have you got gunky, slimy piles of soil erecting all over your lawn? Worm casts can ruin the aesthetics of a perfectly manicured lawn and introduce wicked weeds. But have you considered the benefit of having worms around?

This article explores what causes worm casts and why they’re problematic. We’ll discuss spotting them and why you shouldn’t be so quick to get them gone. If you can’t be convinced, though, you can also find out how to get rid of worm casts completely. 

What Are Worm Casts? 

A worm cast is a small stack of soil that sits on the ground. Worms consume the soil for the organic matter within it. They then excrete the soil, expelling it onto the ground surface. 

And you know that slimy appearance they have? Yes, that’s the worm’s digestive enzymes. Yum.


In the UK, there are three species of worms that cause casts:

  • Common (or lob) Worms (lumbricus terrestris)
  • Black-headed Worms (aporrectodea longa)
  • Grey Worms (aporrectodea calignosa)

As you can probably guess from the name, the Common Worm is the most common, so it visits your garden most frequently. 

Worm casts are particularly troublesome from September to October, as worms love cooler temperatures and rainy days. Worms pop up on wet ground surfaces (typically during the night) to eat, breathe, and reproduce. And, of course, they leave their casts behind.

The Problem with Worm Casts

The main problem with worm casts is their appearance, especially on our lawns. You could spend hours maintaining your lawn so that it’s pristine. Then come the following day, the worms have been at it. Casts everywhere!

If you’re growing your grass long, you may be lucky. Worm casts don’t often show up on long grass. But if you keep your grass short, uh oh! 

Not only do they look ugly, but they’re difficult to remove. It can be incredibly vexing trying to get a worm cast off your lawn and ending up smearing it instead.

Another complication of worm casts is weeds. Weeds love empty spaces. They’ll pop up wherever they can, and they particularly like nestling themselves in between your grass seeds. When worms expel the soil, they leave a gap between grass seeds. This gap is ideal for weeds.

But how do you know when earthworms are around?


Spotting Worm Casts

You know you have a problem with earthworms if you can see the casts springing up on your lawn. You can also see the holes left behind on wet days. They’re usually around 6mm in diameter. 

By their appearance, you can tell the difference between worm casts and regular ant mounds, moles, and mining bees. Worm casts usually form a cylindrical, coiled shape and have a distinctive muddy look. 

On occasion, you may even spot the red-brown worms doing their business. They live in the top part of the soil and can grow up to 200mm in length. Adult worms possess a thick band at the upper end of their body. So keep an eye out! 

Benefits of Lawn-Loving Worms

Yes, worms can be a nuisance, but they actually do a lot of good to your garden. They naturally improve the soil, making it better for your beloved plants. So what are the benefits? Well, worms:


1. Increase soil aeration & improve soil structure

As worms eat the soil, they create little pockets of air throughout. This improves the soil structure as it aids the movement of water, oxygen, carbon dioxide and nutrients underground. All of these goodies are then available to your grass.

2. Maintain the grass and prevent diseases

Lawn thatch is the yellow layer of organic matter that accumulates underneath the green bits of your grass. It’s not popular among gardeners. Worms eat lawn thatch as well as soil. They also consume dead roots and leftover grass clippings. 

Lawn thatch suffers with Dry Patch and Type 2 Fairy Rings – two diabolical diseases that damage your grass. Worms help to diminish the effects of these, too.

Worms, therefore, maintain the overall appearance of the grass. They get rid of all the detritus and hinder the development of diseases.

3. Enhance nutrient accessibility

The digestive enzymes released through excretion concentrate the nutrients, so worm casts are incredibly nutrient-rich. And actually, worms release more nutrients than they consume – up to 11 times more!

Only a tiny portion of worm excrement ends up as casts. The rest stays in the soil. This excretion process makes nutrients more accessible to the grass. Your grass will thank you later!

Worm Cast Removal Methods

If you’re still set on removing worm casts, two methods work best:


1. Pick up and toss

Pick your worm casts by hand and toss them onto the compost bin. Your compost can then benefit from the nutrient-rich soil. 

2. Sweep or pick up and scatter

When worm casts are dry, they can be swept across the ground or broken up and scattered. This makes them less visible whilst keeping the nutrients available for your grass.

Worm Cast Control Methods

Still wondering how to stop worm casts? When attempting to control the number of casts on your lawn, the first decision is whether to go organic or use chemical control.

Natural Control Methods

1. Let your grass grow

Allowing your grass to grow longer will make worm casts less visible. They won’t be gone, but you won’t be able to see them!

2. Reduce the prevalence of lawn thatch

By getting rid of lawn thatch, you eliminate a vital source of food for the worms. This will make them less likely to hang around on your lawn.

3. Remove dead leaves and grass clippings

This takes away another essential food source, also reducing worm numbers.

4. Ditch watering, organic fertilisers and compost

However tempting watering the casts away may be, don’t do it! The wet ground makes worms come up to the ground’s surface – it’ll only encourage more casts. 

Worms love themselves a bit of organic fertiliser, and compost will keep them content for days. If you’re covering your lawn with these, expect more worm casts!

5. Maintain your lawn through top-dressing

Keeping to a yearly lawn maintenance plan is a great way to lessen the effects of worms on your lawn. Using a top-dressing with a high concentration of sand will diminish the lawn’s moisture and make the ground less appealing to worms.


Chemical Control Methods

Iron sulphate is a worm cast treatment that increases the acidity of the soil. Worms hate acidity! Applying an iron sulphate solution every couple of months will cause worms to burrow deeper, leaving your grass free from casts. Use lawn sand for spring and iron sulphate for autumn. Your grass will look greener as a result, too!

Alternatively, use a worm suppressant like Cast Clear or NutriFlo Casting. These products contain certain nutrients which worms don’t like. Once they’ve done their job, the nutrients are at the grass’ disposal.

Worms – Friend or Foe?

So now you know what worm casts are, the issues they cause, and the many benefits of having worms around. What will it be? Will you welcome them in your garden whilst removing any sign of them or kick them to the curb with natural or chemical control methods?

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