Mushrooms in the lawn: causes, common types & treatment

Be it discoloured patches in the grass or small, brown mushrooms in the lawn, fungi in the garden are not uncommon and can appear in many different ways. Discover the different types of lawn fungi and get tips on how to get rid of mushrooms in your lawn.

When we think of mushrooms, we often think of the stems and caps that we see growing from the ground. However, mushrooms mainly grow underground. What we see in the lawn are merely the fruiting bodies that sometimes rise to the surface. Just like microorganisms, the fungal networks beneath the ground are vital for ensuring soil remains fertile. Many fungi live in symbiosis with plants, whereby both fungus and plant benefit from an exchange of substances. However, there are also fungi that damage gardens. These do not live symbiotically, but parasitically, meaning they benefit from the plants, but not vice versa. So, depending on the type of fungus, mushrooms in the lawn can be desirable or lead to trouble.

Why are mushrooms growing in my lawn?

There are many different reasons as to why fungi appear on the lawn. Fungal spores are generally always present in the air and germinate and colonise a site whenever the conditions suit them. Fungi in lawns occur mainly when it is damp and shady, so they feel particularly at home on a heavily mossy lawn. As moss is already troublesome and weakens lawns, fungi have an easier time of making a home there as well. A lawn fungus that lives parasitically on the lawn and damages it is rarely the original cause of lawn problems. Most cap fungi are completely harmless to lawns, but they too are an indicator of disagreeable lawn conditions.

Are mushrooms in the lawn a good sign? Fungi are interesting organisms and not inherently bad. However, since fungi have different requirements to lawn grasses, their presence indicates that conditions are less than ideal for your lawn. A lawn weakened by poor growing conditions is an easy target for weak parasites, whereas a healthy lawn rarely falls victim to them. Therefore, the most important and effective fungus prevention and control tip is simply practising good lawn care.

At a glance: causes of fungi in the lawn

• Airborne spore dispersal
• Fungal hyphae present in the garden soil
• Moisture, including waterlogging
• Too much shade
• Suitable conditions due to improper soil preparation or lawn care
• Dead wood in the garden soil

Which fungi grow in lawns?

First, we must distinguish between basidiomycetes, whose fruiting bodies can be seen above ground, and those fungi that only occur underground. Strictly speaking, some fungi that we know as mushrooms are actually algae. Saprobiontic fungi, which do not depend on trees but on dead, organic material, can grow freely in lawns. We should mention that hardly any edible fungi grow in lawns. The vast majority are inedible, and some are even poisonous. To be on the safe side, and because identifying mushrooms is so difficult, we advise against eating wild mushrooms from your garden. The few edible mushrooms that could appear in your lawn typically turn out to be undesirable for the lawn itself, for example by forming fairy rings.

Tip: fairy rings are circular areas of fungi growing in the lawn. They are formed by the underground fungal network. The rings can consist of the fruiting bodies of the fungi, or of dead or vigorous grass.

Parasol mushroom (Macrolepiota procera)

This edible mushroom is one of the lamellar, or gill, fungi that can be identified by looking under the white-brown patterned gill. One characteristic of parasol mushrooms is the ring on the stalk, which you can move up and down. The parasol can also form fairy rings and be confused with poisonous doppelgangers.

Fairy ring mushroom (Marasmius oreades)

The lamellae of this edible mushroom sit under a broad, flat, light brown cap. It can also form fairy rings in lawns and is easy to confuse with other poisonous mushroom species.

Shaggy ink cap (Coprinus comatus)

The shaggy ink cap is a popular edible mushroom among mushroom connoisseurs. It does not usually form fairy rings in the lawn. However, the white, elongated, downward-drawn umbrella should not be used as a definitive way to identify this mushroom.

Ivory funnel (Clitocybe dealbata)

This garden mushroom is found on meadows and lawns and belongs to the lamellar fungi. It has a flat, mildly funnel-shaped, white to yellow cap, and it can form fairy rings. Ivory funnel mushrooms are poisonous and must not be eaten.

Fairy rings in the lawn

Fairy rings are a well-known but unpopular fungi phenomenon. Fairy rings appear as a ring of mushrooms and can be caused by different types of lawn mushrooms. They can reappear every year and increase in size. The mushroom fruiting bodies may be visible, but the origin lies in the underground fungal mycelium, i.e. the hyphal network. Fairy rings may also become noticeable when rings of grass dry up and die. A distinction is made between three types of fairy rings:

Type 1: there are no mushroom fruiting bodies to be seen, but only a light ring of chlorotic yellow grasses enclosed by two dark green rings. If you dig a little at this spot, you will see the white mycelium in the soil.

Type 2: with this type, the fruiting bodies of the fungi can come to light, as long as conditions allow. Otherwise, only a single, dark green ring is visible, where the grasses grow more vigorously.

Type 3: this is the most visible type, because here the fruiting bodies can be seen. They are often arranged in a ring, but the fairy rings can also form other shapes. The grasses in the inner area of the ring may become yellow and die.

However, fairy rings in the lawn are no reason to panic. You can take action and treat the lawn to prevent further occurrences. As mentioned above, you must address a Type 1 fairy, as these severely damage the lawn. To fight fairy rings, create conditions that are unsuitable for fungi but beneficial for your lawn. If there are visible mushrooms present, carefully cut them off with a knife and dispose of them so that the spores do not spread further. Next, loosen the lawn with a digging fork or similar tool to ensure good aeration in the soil. In addition, sanding the lawn will make it more permeable. To do this, spread lawn sand by hand or with a spreader. Its fine grain size allows it to trickle deep into the aerated lawn. After preparing the soil, sow new grasses in the affected areas. When mowing the lawn in the future, remove the clippings so that the surface of the lawn does not become matted.

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Snow mould in the lawn

Snow mould is also caused by fungi. It appears as light, yellowish spots on the lawn. When it is very humid, the tell-tale grey mycelium becomes visible. Heavily compacted and over-fertilised soil will weaken the lawn grasses, making it particularly susceptible to snow mould. Soil with a high pH value also favours snow mould. Temperatures that are too low or too high will prevent the spread of snow mould. Snow mould prospers in autumn and spring when it is colder and rains more frequently. It mainly occurs at temperatures of 0 to 10 °C. This fungus was given the name snow mould because the ideal conditions for the disease occur under a blanket of snow in spring. The fungal pathogens are mostly Microdochium nivale or Monographella nivalis.

Snow mould disappears with rising temperatures, so control is not absolutely necessary.

• Help prevent snow mould by scarifying and sanding the lawn to ensure good permeability and aeration and by removing cuttings and leaves from the lawn.
• Strengthen your lawn before winter with a potassium-rich autumn lawn fertiliser, such as our Plantura Autumn Lawn Feed. Strong lawns are better equipped against a winter fungal attack. Our fertiliser also promotes active soil life, which is equally important for a healthy lawn and soil.

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Red thread

Red thread disease in lawns is caused by the fungus Laetisaria fuciformis. It initially manifests as light, yellow or red patches on the lawn. Lawns that are weakened or stressed by poor weather are particularly susceptible to red thread. Whilst the disease can occur all year round, but is less likely in winter and summer. Temperatures of 5 to 30 °C are necessary for an outbreak. Especially when it is humid outside, the fungal mycelium, which looks like pink thatch, can be seen on the infested grasses. In addition, red or pink outgrowths that look like antlers can form on the grasses.

Since red thread disease in lawns occurs more often in warm, humid weather and on weakened lawns, proper lawn care is crucial:

• Avoid watering the lawn too frequently or too heavily so that the moisture does not remain on the grasses.
• Ensure the grasses are getting enough nitrogen, especially in spring.
• To prevent matting and moss formation, fertilise and mow the lawn regularly. Remove the cuttings, and dethatch the lawn every few years.

Stem base rot

Stem base rot mainly affects grasses in the seedling stage. The pathogens of stem base rot are fungi of the genus Pythium. Warm, humid weather favours the outbreak of this disease. It is recognisable by the rotting shoot base of the seedlings, as well as by black, dying roots. More developed lawns can also be infested and develop into brown, slimy areas. The brown roots of the grasses are completely decomposed over time, and gradually, the entire lawn can be affected.

• Aerating and sanding works wonders for lawns with stem base rot problem areas. Matted lawns should be scarified.
• It is also advisable to water in the morning hours so that the water can evaporate during the day and does not remain as a damp film on the grass blades.

Other fungi in the lawn

There are more lawn fungi that are not as common in gardens, but do grow in meadows and can show up in lawns from time to time:

• Giant puffball (Calvatia gigantea)
• Horse mushroom (Agaricus arvensis)
• Shaggy parasol (Chlorophyllum rhacodes)
• St. George’s mushroom (Calocybe gambosa)
• Livid entoloma (Entoloma sinuatum)

How to get rid of mushrooms in your lawn

Eradicating fungi from the lawn is difficult. It is better to focus on taking preventive measures to prevent the fungi from getting a foothold in the first place. To this end, good soil preparation before planting or replanting the lawn is the best defence. Regular maintenance is also important in preventing fungi. The following measures are effective in preventing mushrooms in your lawn and keeping it healthy:

• Aerate the lawn down to the roots. Topdressing with sand also makes the soil more permeable.
• Scarify regularly to remove lawn thatch and moss and to aerate the turf.
• Remove leaves and lawn cuttings from the lawn.
• Water in the morning to prevent moisture from remaining on the surface for a long time.
• Fertilise appropriately with sufficient, but not too rich in nitrogen, especially in autumn.
• Ensure the right soil pH: find out how to lime a lawn properly here.
• On heavy soils, mow occasionally and remove the cuttings to prevent the formation of thatch.

To remove mushrooms from the lawn, cut the fruiting bodies off with a knife and dispose of them. However, the fungi will continue to live under the soil, so you will need to make the garden soil unattractive for harmful fungi. It is important to have a pH value that suits the soil type and ensures a healthy lawn. If the soil pH is too low or too high, follow the appropriate measures. If the pH is too low (acidic), liming the lawn will raise the pH. The lime helps to bring acidic soils back into a suitable range for the lawn.

Do fungi in the lawn disappear by themselves? The fruiting bodies of the fungi will disappear by themselves. However, as long as the underground mycelium remains, the fruiting bodies will reappear. To prevent this, you must practise proper lawn care.

Unfortunately, fungi can easily make a home underground in soils and the spores stick to organic material. This is why it is possible for a fungus to sprout from purchased potting soil and spread in your raised beds.