Mushrooms in the lawn: where they come from and what really helps
In autumn they often appear in the lawn overnight: small brown caps, sometimes on their own, sometimes in a circle. Most mushrooms do not harm the lawn. But they show you what is going on in the soil. Here you can read which mushrooms are harmless, when you should act and how to get rid of fairy rings for good.
In short
- The mushrooms you see are only the fruiting bodies. The actual fungus lives in the soil as a fine network (mycelium) and breaks down organic material there.
- Individual capped mushrooms are harmless and disappear on their own after a few days.
- The causes are usually thatch, buried wood, waterlogging or long damp spells.
- Fairy rings can damage the lawn because the mycelium makes the soil water-repellent. Aeration and deep watering help against this.
- Fungicides are not a solution in the home garden. They hardly reach the mycelium in the soil and harm soil life.
What you see is only the tip
A fungus in the lawn consists mostly of fine threads in the soil, the mycelium. It breaks down dead plant material such as thatch, old roots or buried wood. The caps that appear overnight are only the fruiting bodies with which the fungus spreads its spores. So if you mow off the caps, the fungus is not gone. It forms new ones the next time the weather is damp.
Which fungi appear in lawns?
| What you see | What it is | Does it harm the lawn? | What to do |
|---|---|---|---|
| Individual capped mushrooms, scattered | Decomposers of thatch and organic material | no | mow off or leave, reduce thatch |
| Mushrooms in a line or group | Fungus above buried wood or old roots | no, disappears once the wood has rotted | dig out wood remains if possible |
| Mushrooms in a circle, lawn dark green in the ring | Fairy ring, mycelium releases nitrogen | hardly, it just looks uneven | fertilise evenly, aerate the ring |
| Brown, dry ring, often with a dark green edge | Fairy ring, mycelium makes the soil water-repellent | yes, the grass dries out in the ring | aerate the ring intensively, water deeply |
| Yellow or grey slimy mass on the grass | Slime mould, not actually a fungus | no | rinse or sweep off, disappears in dry weather |
| Spots, coatings, red threads on the grass | Lawn disease, for example snow mould | yes | see the article Lawn diseases |
Important
Some lawn mushrooms are poisonous. If small children or dogs play in the garden, collect the fruiting bodies regularly, ideally with gloves, and dispose of them in the household waste.
Why now? The causes
Fungi need moisture, mild temperatures and food. In late summer and autumn all of these come together.
- Thatch: a thick layer of dead grass is the main food for many lawn fungi. The more thatch, the more mushrooms.
- Buried wood: old tree stumps, roots or building timber in the soil are broken down over years. Mushrooms keep appearing above them.
- Waterlogging: wet, dense soil keeps the mycelium moist. More on this in Waterlogged lawn.
- Shade and little air movement: under trees and along hedges the lawn dries more slowly after rain.
- Watering in the evening: if the lawn stays wet overnight, fungi find ideal conditions. Water early in the morning instead.
Fairy rings: the only fungus that really causes trouble
A fairy ring forms when the mycelium spreads evenly outwards from one point, often over years. A typical example is the fairy ring champignon. Depending on what the mycelium does in the soil, the ring looks different.
| Appearance | What happens in the soil | Problem |
|---|---|---|
| Just a circle of mushrooms | The mycelium grows without affecting the lawn | purely cosmetic |
| Dark green ring | The mycelium breaks down organic material and releases nitrogen, the lawn grows more strongly there | uneven appearance |
| Brown, dead ring with a green edge | The dense mycelium coats the soil particles and makes the soil water-repellent, the grass dries out | real damage |
The brown ring is the same problem as dried-out soil after summer: water beads up instead of soaking in. More on this in When soil repels water.
How to get a fairy ring under control
- Aerate the ring: aerate the brown ring and about 50 cm beyond it densely with hollow spoons. The holes break up the water-repellent layer. Do not spread the cores from the ring around the garden, as they contain mycelium.
- Water deeply: straight afterwards, water several times in a row until the water really goes down deep. For stubborn rings, a wetting agent from a specialist retailer that makes the soil wettable again helps, or the soil lance, with which you get the water directly below the impermeable layer.
- Top-dress with sand: fill the holes with quartz sand so that they stay open.
- Fertilise evenly: this evens out the dark green edge visually.
- Repeat: a fairy ring rarely disappears completely. With two to three treatments a year you keep it in check so that the lawn stays green.
Tip
Cutting out the turf in the ring and replacing the soil only makes sense for very severe rings. The mycelium often reaches 20 cm and deeper and grows beyond the edge of the replaced area. In most cases aerating and watering is the better route.
Preventing fungi
| Measure | Why it helps | When |
|---|---|---|
| Remove thatch | deprives the fungi of food | spring or late summer |
| Aerate and top-dress with sand | the soil dries faster, less waterlogging | spring and autumn |
| Water in the morning instead of the evening | grass and soil dry off during the day | throughout the season |
| Remove clippings and leaves | less food and moisture at the surface | every time you mow, regularly in autumn |
| Balanced fertilising, potassium-rich in autumn | strong grasses, less nitrogen in late autumn against snow mould | spring and late summer |
Note for reel mowers
You can safely mow off mushroom caps with a reel mower. If leaves lie on the lawn in autumn, it is better to mow with a rotary mower so that twigs do not damage the reel.
What you should avoid
| Common tip | Why it does not help |
|---|---|
| Spraying fungicides | The mycelium in the soil is hardly reached, and soil life suffers too. Not a solution in the home garden. |
| Spreading lime against fungi | Lime only helps if the soil is verifiably too acidic. Have a soil analysis done first. |
| Pulling out mushrooms and leaving them | The caps rot in the lawn and release their spores as they do. Better to mow them off with a grass box or collect them. |
| Fertilising more to make the lawn stronger | Too much nitrogen in autumn makes the lawn susceptible to snow mould. |
Frequently asked questions about mushrooms in the lawn
Are mushrooms in the lawn a bad sign?
Not necessarily. They show that organic material is being broken down in the soil. Lots of mushrooms point to too much thatch or too much moisture.
Will the mushrooms go away on their own?
The caps will, usually after a few days. The mycelium remains and forms new ones when the weather is right. You only get fewer mushrooms in the long run if you tackle the cause.
Do mushrooms harm my lawn?
Individual capped mushrooms do not. Only fairy rings with a brown inner ring cause damage, because the soil there no longer takes up water.
Can I just mow the mushrooms off?
Yes. Ideally with a grass box, so that the spores are not spread.
What is the white coating on the lawn in spring?
That is usually snow mould, a lawn disease. More on this in Lawn diseases.
Tools against fairy rings and thatch
- Lawnpecker: hollow spoons open up the soil in the fairy ring, the cores land straight in the collection tray and are not spread around the garden.
- Soil lance: gets water directly below the water-repellent layer.
- REWUKIL: for dethatching and against thatch.
- Levelling rake: for working in the sand.
