Fairy Ring in Lawns: What Causes It and What Can You Do?

Fairy ring can be one of the more unusual problems to show up in a lawn. You may notice a dark green circle or arc of grass, mushrooms growing in a ring, or in more severe cases, a ring of declining or dead grass.

Unlike many lawn diseases, fairy ring is primarily happening in the soil. The fungus is living below the grass and feeding on organic material. Understanding what is happening underground helps explain why fairy ring can be difficult to eliminate.

General Overview

Fairy ring is caused by naturally occurring fungi living in the soil. These fungi feed on and break down organic material such as old grass roots, thatch, buried wood, and other decaying plant material. This decomposition is a normal biological process in healthy soil. The problem develops when the activity of the fungus begins to noticeably affect the grass growing above it.

Fairy ring often grows outward through the soil, which is why symptoms frequently appear as circles or arcs.

It is important to understand that fairy ring is not something falling onto the lawn or being caused by something applied to the grass. The fungal activity is primarily occurring within the soil and organic material beneath the lawn.

How to Identify Fairy Ring

Fairy ring can look different depending on how the fungus is affecting the soil and grass. Common symptoms include:

• Dark green rings or arcs of rapidly growing grass
• Mushrooms appearing in a circle or arc
• A dark green outer ring with stressed grass inside
• Brown or dead grass forming a ring
• Soil inside the affected area that becomes difficult to wet

The rings can gradually become larger as the fungus continues growing through the soil.

Why Does Fairy Ring Happen?

The fungus responsible for fairy ring is feeding on organic material in the soil. There are two primary ways this activity can affect the lawn.

• Dark Green Fairy Rings – As the fungus breaks down organic material, nutrients including nitrogen can become available to the grass. The additional nitrogen causes the grass where the fungus is active to grow faster and become darker green than the surrounding lawn. The grass itself may be completely healthy. It simply looks different because it is receiving more available nitrogen.
• Fairy Rings That Damage Grass – Some fairy ring fungi can create water repellent conditions in the soil. Instead of water soaking evenly into the root zone, the affected soil begins resisting water. Grass roots then struggle to receive enough moisture even when the lawn is being irrigated. Eventually the grass can become stressed, turn brown, and die.

Common Misconceptions About Fairy Ring

• The mushrooms are causing the problem – Mushrooms are simply the visible fruiting structures of fungi already living in the soil. Removing the mushrooms does not remove the fungal network underneath the lawn.
• Fairy ring came from something put on the lawn – The fungi involved in fairy ring live within the soil and organic material. Their activity is part of the natural decomposition process occurring underground.
• More fertilizer will kill the fungus – Fertilizer does not eliminate fairy ring. It can sometimes help make a dark green ring less noticeable by improving the color of the surrounding lawn.
• Fungicide will permanently eliminate fairy ring – Fairy ring can be difficult to control because much of the fungus is living below the turf surface. Fungicides may suppress fungal activity and reduce symptoms, but they should not be viewed as a guaranteed permanent cure.

What Can You Do Once You Have Fairy Ring?

There are generally two approaches.

1. Manage and Mask the Symptoms

For many lawns, this is the most practical approach.

If the fairy ring is mainly producing darker green grass, properly fertilizing the surrounding lawn can help reduce the color difference.

Watering is especially important. Deep watering and improving water movement into the affected soil can help reduce stress on the grass.

The goal is not necessarily to eliminate the fungus. Instead, the goal is to keep the grass healthy enough that the fairy ring becomes less noticeable.

2. Remove the Affected Soil

For severe or persistent fairy rings, the more aggressive option is to physically remove the affected turf and soil.

The affected soil and organic material surrounding the fairy ring must be removed and replaced with clean soil before the lawn is reestablished.

This can be disruptive and labor intensive, which is why it is generally reserved for situations where fairy ring has caused significant damage and the homeowner wants the best opportunity for physical removal.

What Can bioLawn Do Once You Have Fairy Ring?

Our goal is usually to reduce the symptoms and help the lawn remain healthy. Depending on the severity of the fairy ring, we may recommend a combination of:

• Proper fertilization to help blend dark green rings with the surrounding lawn
• Water management to reduce drought stress in affected areas
• Treatments designed to improve water movement into the soil
• Fungicide applications to suppress fairy ring activity when appropriate

Because the fungus is living within the soil, treatment does not guarantee that fairy ring will disappear completely. Managing the condition over time is often more realistic than trying to completely eradicate it.

What Can You Do to Prevent Fairy Ring?

Unfortunately, there is no reliable way for a homeowner to completely prevent fairy ring. The fungi responsible for fairy ring are naturally present in soils and feed on organic material that is also naturally present.

Removing buried wood, old tree roots, and other large amounts of decaying material when possible may reduce potential food sources for the fungus.

Maintaining healthy turf through proper watering, mowing, and fertilization can also make the lawn better able to tolerate problems when they occur.

What Can bioLawn Do to Prevent Fairy Ring?

There is no lawn treatment program that can guarantee fairy ring prevention. Our focus is instead on maintaining healthy grass and soil so the lawn is better able to tolerate environmental stress and fungal activity.

If fairy ring does develop, identifying it early gives us the opportunity to determine whether it is simply causing a cosmetic color difference or whether it is beginning to interfere with water movement and damage the grass.

The Bottom Line

Fairy ring is caused by fungi living naturally in the soil and breaking down old plant material and other organic matter.

Sometimes that process releases nutrients and creates a dark green ring of rapidly growing grass. In other situations, fungal activity makes the soil water repellent, causing the grass above it to become drought stressed and potentially die.

There is no simple way to eliminate or prevent fairy ring. In most lawns, the best approach is to manage the symptoms with proper watering, fertilization, and targeted treatments when appropriate. For severe cases, removing and replacing the affected soil is another option.