What is Slime Mould?
Slime mould is a naturally occurring organism that occasionally appears on healthy lawns, often following warm and humid weather. Although its sudden presence can look concerning, it is entirely harmless to grass, pets, and people. This brief aims to provide clarity and reassurance about what slime mould is, why it appears, and how it can be managed.
What Is Slime Mould?
Slime mould is a primitive organism that feeds on decaying organic matter, bacteria, and microscopic particles within the lawn. It is not a disease, fungus, or pest; rather, it is a beneficial part of the natural ecosystem. It thrives in moist conditions and may form patches of grey, yellow, white, or even purple, sometimes resembling a powdery or jelly-like substance on the surface of the grass.
Why Does It Appear?
Slime mould typically develops when conditions are favourable, particularly during:
- Warm and humid spells
- Periods of heavy rain or overwatering
- Shaded or densely thatched areas of turf
- Lawns with high organic content
These organisms are usually more visible in late spring through autumn, especially after sudden weather changes.
Is It Harmful to the Lawn?
No. Slime mould does not damage the grass or its root system. It sits on the surface and uses the lawn simply as a support structure. Grass may temporarily look dull where the mould rests, but the turf recovers fully once the mould disappears.
How to Manage Slime Mould
In most cases, no treatment is required. Slime mould typically dries out and dissipates naturally within a few days. If removal is desired, light mechanical action is sufficient:
- Gently brush the affected grass with a stiff broom or rake
- Mow the lawn as normal to disperse the spores
- Improve airflow by reducing thatch and controlling shade
- Avoid excessive watering during humid periods
Chemical treatments are neither necessary nor recommended.
