Mushrooms and Toadstools in lawns
Author: Stefan Palm Date Posted: 4 April 2023
During the autumn and winter, mushrooms and toadstools are common in lawns. The questions we get asked most are, "Will they damage my lawn? and How can I get rid of them?"
In my recent walks around our neighbourhood, in local national parks and even in my own home lawn, I've seen quite a lot popping up of all manner of shapes and sizes, ranging from typical white mushrooms and toadstools to bright orange blobs on the ground. It's unusual for them to be out this early; however, there is no denying that they are around.
The mushrooms that you see on your lawn are part of a much larger fungal organism. They are the flowers, if you like, or more accurately, spore-producing structures of some kinds of fungi. The rest of the organism (often 90% or more) is underground and is known as mycelium. While you only see mushrooms and toadstools for a short time of the year, the mycelium is there in your soil year-round. For the better part, most of these fungi are beneficial. They feed on organic matter in the soil, such as thatch, decaying leaves and tree roots, breaking this matter down and releasing nutrients back into the lawn.
Mushrooms and toadstools produce spores, which blow about in the wind. As the weather cools down, these spores land in and around lawns and germinate, sending out long threadlike strands into the soil called hyphae. In time, these hyphae bunch together and thicken up to form the mycelium that I referred to earlier. Mycelium looks like a white cotton substance that you'll often encounter when digging around in the soil. Given that the fungus feeds on organic material, it is common to see mushrooms popping up where a tree used to be. I took this photo to demonstrate this effect. Notice the pattern of mushrooms following a line of roots from an old tree.
How do you control mushrooms and toadstools in your lawn?
Let me start by saying that the fungi that produce the mushrooms are harmless to lawns. Since they have little effect, you can leave them where they are; however, if you don't like the look of them or are concerned that they may be toxic, you can remove them. If you want to go about getting rid of them, there are a couple of ways that you can go about it.
- Physically remove them. There is no fungicide that will kill them off, so the only way to remove them is to physically pick them. This will be an ongoing process, and they will come back. Since they are a product of the mycelium in the soil, new ones will continue to grow while conditions are favourable.
- Remove their food source. One of the best ways to stop them from coming back is to remove the food source the fungi are feeding on. If it is a tree root like in the photo, then by removing the root you will most likely remove the fungi too. In circumstances where the fungi are feeding on material like thatch or decaying leaf litter in the soil, it can more difficult to stop mushrooms from growing. In these cases, you may have to resign yourself to continue picking the mushrooms as they appear.
Are there circumstances where mushrooms are an indication of problems?
Yes. There is a fungus called a fairy ring. A fairy ring is a fungus that presents as a ring in your lawn. The ring starts as a small discoloured circle in your lawn and then, over time, grows larger and larger. Depending on the time of year, you may notice mushrooms growing in the ring itself; however, this isn't always the case. Once again, there is no fungicide to control fairy rings, but it will in time, grow out of your lawn. Notice in the photo here that there is only a narrow band of affected lawn (in which the mushrooms grow). This is where the mycelium is most concentrated. As the ring grows out, the lawn in the middle generally recovers; however, this recovery will happen much faster with some intervention from you. The life cycle of the mycelium in fairy ring is generally fairly short, and as it dies, it leaves behind an oily residue in the soil. This leaves the soil non-wetting or water-repellent, which is one of the major reasons you're seeing dead or dying lawn in the shape of a ring. You can help overcome this with regular applications of a liquid wetting agent as the fungi grows out to make sure your soil absorbs water properly in the future.
To answer my earlier questions, will mushrooms and toadstools damage my lawn? - in most instances no. At worst, they may contribute to making your lawn non-wetting which can be overcome with a liquid wetting agent. Can you remove them? Yes- by picking them, but to stop them from coming back, you'll need to remove their food source, which isn't always possible.
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Reference: Ed Perry from the University of California Cooperative Extension.