Those small piles of soil you're seeing on your lawn are most likely earthworm casts.
What Exactly Are These Piles?
According to horticultural information, the small mounds of soil you notice on the surface of your lawn, especially from late autumn through to spring, are known as casts. The casts are the work of earthworms that live in the root zone of the soil. Essentially, they are the excretions of earthworms after they have consumed soil and organic matter.
These casts are a natural part of the soil ecosystem. Earthworms digest the soil, extracting nutrients and organic material, and then deposit the processed soil back on the surface. This process actually helps to improve soil structure and fertility over time.
Why Do Earthworms Create Casts on the Surface?
Earthworms consume soil containing organic matter. As they tunnel through the soil, they ingest it, process it through their digestive system, and then deposit the leftover material. When conditions are right, particularly when the soil is moist and temperatures are cool (like in late autumn to spring), earthworms are often more active closer to the surface, leading to the deposition of casts there.
Managing Earthworm Casts on Your Lawn
While casts indicate a healthy earthworm population and good soil, they can sometimes make the lawn surface uneven or look messy.
When They Appear
As the reference states, you will most commonly notice these mounds over the late autumn through to spring period. This is often when the soil is cool and moist, favorable conditions for earthworm activity near the surface.
Potential Impact
- Can make the lawn surface bumpy.
- Can be smeared across the grass when mowed or walked on while wet, potentially creating bare patches or encouraging weed growth.
What You Can Do
Managing casts is usually about minimizing their surface impact rather than removing the earthworms (which are beneficial).
- Wait for them to dry: Allow the casts to dry out before taking action.
- Brush them off: Once dry, you can simply brush them off the lawn using a stiff broom, rake, or even a besom broom. This distributes the soil and nutrients back into the lawn without smearing.
- Avoid mowing when wet: Don't mow the lawn when the casts are wet, as this will smear them.
- Regular aeration: Improving soil drainage can sometimes reduce surface casting by encouraging worms to stay deeper.
It's important to remember that earthworms are beneficial to your lawn's health, improving drainage, aeration, and nutrient cycling. Casts are simply a visible sign of this activity.
