Mushrooms in Your Lawn

You might love mushrooms on your pizza, but not popping up in your lawn. Are mushrooms in your lawn something to worry about, or just a unsightly nuisance? Let's take a closer look at mushrooms.... Mushrooms are the fruiting part of some fungi, and fungi are extremely important in our gardens. We tend to focus on the types of fungi that cause problems and disease, but many other types of fungi are essential in in garden health  through organic matter decomposition, feeding and protecting plants. Mychorrizal-type fungi break down organic matter in the soil to help feed plants and trees in exchange for receiving energy providing sugars from the plant (the sugars made by the plant through photosynthesis). Here's the neat part; these fungi have evolved beyond this simple exchange, and have become protectors of their host plants. If a smaller tree in a forest is struggling and needs nutrients, the fungi can detect this and they send signals to other, stronger trees, who can then share nutrients with the struggling tree.  It doesn't stop there...if one plant in your garden is under attack by aphids, the fungi communicate through their hyphae network to warn other plants about the impending attack so they can better prepare themselves to defend against it. OK, back to the mushrooms in your lawn - are they the good type, the decomposing type or the helpful type? Typically the white and brown mushrooms you see on your lawn are the decomposing type and they readily pop up after an extended period of warm and wet weather. They are sometimes associated with decomposing wood or roots under the ground or anytime that organic matter is being decomposed, especially in the right the conditions (rainy, hot and humid weather).  These ones will not cause a problem for your lawn.

  1. Mushrooms in your lawn are indicators of over irrigation, over fertilizing or that a build up of thatch. Aerate your lawn to remove thatch and slow down on the amount of water and fertilizer you are adding.  If they have popped up after a long period of rain, aeration will still help by improving your lawn's drainage and limiting the amount of thatch that builds up.
  2. If you have an existing tree in the area that is showing signs of poor health, the mushrooms could be there decomposing dead or dying roots under the ground. We recommend calling in a certified arborist to take a closer look at the tree health.
  3. If there was a tree in the area previously, or if there is any buried wood underground, the mushrooms are likely decomposing that wood. You can go to the trouble of digging it up, or just let the mushrooms do their job, breaking down the wood and returning valuable nutrients to the soil.

You only have to remove these mushrooms if you don't like the look of them, or if you are worried about pets or young children eating them. Since identifying poisonous mushrooms from safe mushrooms is a task best left to the experts, the safest strategy with kids and pets is to assume they could all be trouble, so remove them all by hand as soon as they appear, or restrict kids and pets from having any access to the area.

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When is fungi in the lawn the bad type?

  • If you have rust, brown patch, necrotic ring spot, leaf spot or powdery mildew in your lawn  - These are all types of bad fungi that effect lawn health. They are almost always caused by poor lawn management and/or poor growing conditions. Practicing proper lawn management will help combat these diseases (aeration, reduced irrigation and fertilization, top dressing, over seeding with mixed grass types and proper mowing and watering techniques).
  • If you have large circular ring of many mushrooms, or of noticeably darker green grass, you likely have a fairy ring - The dark green  grass is where the fungi underground have increased nutrient availability to that area and when the conditions are right (hot and humid), the mushrooms pop up from the soil around the ring. The only concern with these is that the mushrooms become so dense that the grass growth is affected or with the ugly look of dark green circles in your lawn. Removing these is a challenge since they extend to far underground. Your best bet? You guessed it, practice good lawn management!

Interested in learning more about the wonderful world of mushrooms? The Toronto Mycological Society promotes an interest in and appreciation of fungi and their role in nature. - Written by Aileen Barclay #TeamFrankie