Managing Mushrooms

Thanks to a synergistic timing of rains, warm temperatures and summer fertilization, many of you may be seeing a bumper crop of mushrooms in your lawns and flower beds. So, I’ve been getting lots of questions about controlling them.

The answer: There’s no need to!

Thanks for your time, drive safely, and have a great weekend. 

Okay, I'll give you a little more information, but remember that it’s not necessary to control mushrooms.

Let's start with the ones in the turf.  They’re commonly referred to as "fairy rings," (BELOW) and any plant pathologist will tell you these mushrooms don't damage a lawn, so just ignore them.  In fact, you can probably pat yourself on the back for the high level of organic matter in your yard – that’s what this type of saprophytic fungus is feeding on, just under the soil.

They will continue to appear when wet weather is followed by warmer temperatures, as long as there is organic wood or thatch for the fungus to feed on. Once it has all been consumed, the mushrooms will disappear.  That often takes several years, though, so if these mushrooms really bother you, you can rake them out or pluck them up when they appear.  There is no "silver bullet" spray that will make them go away -- not without killing all the good fungal spores and good bacteria in the soil.  Still, there are a couple of topical fungicide treatments that can reduce their numbers. I’ve long recommended Consan Triple Action 20 for this. And for a true organic method, dust them with agricultural sulfur.

I’m also often asked if such mushrooms are poisonous. The organic matter in which a mushroom grows is what can make it poisonous, so while those growing in a lawn may not typically be lethal if consumed, it is unwise to eat them. It’s best to assume that any mushroom in your yard is poisonous, and I’ve always said it’s never worth taking a chance - you should assume they are poisonous unless you know otherwise for certain.  Even if those in your lawn aren't poisonous by definition, they can still be somewhat toxic, capable of generating stomach discomfort. 

Other mushrooms pop up under living trees. Many of those are from beneficial mycorrhizal fungi. Basically, they're living in association with the roots of the tree, and sometimes they help the tree take up nutrients. Again, there is very little need for control since they are more a curiosity than a problem.

Mushrooms that appear in mulched landscape beds are affectionately referred to as “slime molds.” These are primitive microorganisms that can produce white, yellow, orange or brown blobs or patches of fungus-like material known as sporangia (spores).  When mature, these masses become powdery and break apart easily during rain or when knocked around by your shoes. The spores survive in soil or organic debris and germinate during wet weather to form motile swarm spores. Some fuse together and become amorphous amoeba-like structures that engulf other organisms or organic matter. Slime molds can actually move or flow across soil or plant surfaces, and although unsightly, they are not pathogenic to living plant material. For more info, read my my tip sheet on fungus in mulch.  

 In conclusion, just remember that most mushrooms are a sign of good things in the soil. So, you don't need to attack them with an arsenal of sprays or dusts. If you feel a need to control their spread, just pluck or rake them away before they open up. I've given you a couple of light treatments, but if you've found success with another method of elimination, send me an email.

IMAGES: Top - Getty Images; Fairy Ring - Famartin
GardenLine with Randy Lemmon

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