Fairy rings are a group of diseases found in turf grasses that are caused by fungi. The fungus sprouts lots of small threads, called mycelium in an arc or circular shape. What causes the fungi to start growing in the first place is still not clear, however often lawns that have a substantial thatch layer as well as being heavily compacted, will have a higher probability of developing fairy rings. All types of lawns can be affected and they can exist all year round but only become really obvious in the summer months or during prolonged periods of dry conditions. There are 3 types of fairy rings which are all different in appearance.
The type 1 fairy ring is usually found on fairways, outfields or domestic lawn areas as opposed to areas of fine turf. This is the most common type of fairy ring and is particularly evident in dry weather. It consists of a ring of dead grass bordered by a strip of very healthy green grass. The soil below the ring will more than likely be very compact and sometimes colonised by patches of moss. The soil itself smells very musty and will have white specks running through it. These white specks are the mycelium fungus and this is what causes the soil to become water repellent. This means that very little moisture is able to reach the root zone layer of the grass, leading to the grass to die off. Once the ring dries out, it becomes very hard to re-wet and may only reabsorb water properly during the wet autumn/winter periods.
The type 2 fairy ring are areas of stimulated grass growth with a lush ring of very actively growing grass with or without toadstools. These areas usually grow at a much faster rate than the rest of the lawn. They don’t damage the grass plant or cause the soil underneath to become hydrophobic. These fairy rings are entirely confined to the thatch layer of the lawn, so regular scarification would be particularly important as a prevention method. They are more common on areas of more finer turf and can be masked to a certain degree by applying a nitrogen or iron based feed.
The type 3 fairy rings are very common and also have no detrimental effects on the grass plants health. They don’t create bare patches or areas of lush growth. Instead, they create a ring of toadstools which are only usually obvious in the spring or autumn months during wet weather. They occur more in areas of poor drainage or areas that receive large amounts of rainfall. There is no remedy although picking, brushing or mowing the toadstools to prevent further spore production is a good preventative measure to keep them under control.
Dealing with Fairy Rings
There are a few options available in terms of preventing fairy rings. Firstly, a non chemical approach would be to keep the affected area well spiked with a garden fork, making sure to spike the entire ring as well as half a metre each side of the ring. The deeper you are able to spike the better. This will aid water penetration to the root zone layer.
Scarifying regularly to remove substantial layers of thatch is also extremely beneficial. This is because Fairy rings can form as fungus that feeds on dead organic matter in the thatch layer. Reducing the amount of lawn thatch will take away some of the food that the fungus subsequently feeds on, reducing the chances of fairy rings forming.
Another option would be to apply a wetting agent as this will break down the water repellent properties of the soil. A single treatment wouldn’t cause a massive difference however after repeat applications, the lawn will start to respond.
A chemical solution would be to apply a fungicide in the springtime months when the fungus is actively growing. This treatment isn’t a cheap option and there is also no guarantee one application will be successful either.
Alternatively, the most extreme option would be to dig the fairy ring out, making sure to dig about 1 metre deep and half a metre each side of the ring, followed by filling the space left with fresh soil. There is also no guarantee with this that the fairy ring will not return.