They are just a visual representation of organic matter decay going on beneath the soil surface. Could be existing old roots from a long removed tree or shrub, the fence itself (if in contact with or partially buried by soil) or just whatever organic matter may be present from the imported soil or mulch. Harmless and very temporary.

That's a magnificent spread of shrooms, though!

Fori, I agree they are impressive but they’re also a little scary since there are sooo many more than last year when they first showed up! They’re quite large too.

gardengal48, 11 years ago when we began installing plants we spread a truckload of microbial mulch to healthy up the soil that was brought in after our yard was graded to level for hardscape. I can‘t imagine all these years later that mulch is still active but I do attempt to be as organic in my garden practice as I can be. It’s just so startling to suddenly see these huge white mushrooms pop up!

The look remarkably like ordinary edible field mushrooms. Did you use any mushroom compost? There might have been some spores. I am NOT recommending you eat them.

Mild and damp falls are prime mushroom growing conditions and both are plentiful in the PNW! I often have similar looking shrooms popping up in various places in my garden only to see them vanish in a day or two. The oddest are those that spontaneously appear in the middle of my lawn with no close or obvious decaying organic matter to be found. And not fairy ring mushrooms either, but big, beefy colonies like those in your photos.

I have fairy rings growing in the back. Perfect 10' to 20' circles of mushrooms in the grass and think they look cool until I mow them over. from what I understand the body of the fungus is in the ground and the mushrooms are for reproduction of spores and removing them would make no difference.

Thanks everyone! So I’ll just leave them alone until spring. Maybe the squirrels, birds and raccoons that visit my yard will find them tasty. Kevin, it seems like if the a ground growth of mushrooms are for the spores to reproduce, my pulling them up would’ve reduced their population. Maybe I spread those spores by handling them? Fori, if your kids are

mushroomophobic, seeing these might send them over the edge!😆

They'll be long gone by spring. I still think they look a lot like regular Agaricus campestris or a related grocery mushroom. The upside down ones are dead ringers. What is “microbial mulch”? What is in it?

a free show of ma nature.. why not just enjoy it for the weirdness it is ...

shrooms are one of natures biocomposters.. using up whatever is in the soil that they need ... and when they finish with that... they wont come back ...

frankly.. i think its cool.. and wonder why you want to 'fix' it ... just enjoy it ... you must have other things to do or worry about ...

what might even be cooler.. is all the moss on the cement ... that might be an indication of how much moisture is there all the time.. but im not even sure thats a problem ... though that cement got the wood fence off the ground.. so probably extended its life significantly ... though i might make sure it doesnt start creeping up the wood ... maybe running something under the board to insure air gets in there.. or that horizontal board might start rotting ...

ken

Ken_adrian, I didn’t want to fix the shrooms but was concerned they might be telling me there’s a problem I’m unaware of since this year’s crop is sooo much larger than last year when they first showed up. I certainly do have a plethora of other things to worry about, as do we all! The shrooms were a welcome distraction!.☺️The moss on cement wall is pretty cool & it is pretty moist along the wall since it’s at the base of a short slope but mostly because I am in WA, Pacific Northwest country where we are blessed with wet, usually temperate winters unlike where you live. Moss is one of the reasons Washington is called the “Emerald State”! The fence does have a clear gap between the vertical fence boards & cement wall top. The horizontal board is simply trim to cover the gap. Fence also has metal posts embedded into the wall as the supports rather than fence posts in the ground. I appreciate you bringing that up though in case it was an issue.

floral_uk, “Microbial Mulch” was called Mighty Microbe Mulch by the fellow who created and sold it. It was touted as a beneficial mulch much preferable to our usual bark dust used to keep flower beds tidy & weed free. The benefits of this mulch were listed as provides micronutrients, nearly neutral pH 8.0 ( we have acid soil in PNW), retains water, pasteurized, low in salts, supplies humic & fulvic acids (whatever those are). I did notice a lot of evidence of decay going on - whitish soil - when I turned or dug into soil where I’d spread this mulch for a couple years afterwards & it was a lovely dark rich looking color. And, rest assured, I didn’t take your remarks on my mushrooms as a dining recommendation! I’m sure they’re not “magic” either 😆

I wonder if the Mighty Microbe chap used spent mushroom compost in his mixture?

floral_uk, Mighty Microbe may have used mushroom compost in mix but it was 2014 when we spread that stuff around so doubtful that’s the cause. When my home was built in 2012 builder added the 4’ high cement retaining wall the whole length of 6 homes back yards to reduce the slopes in back yards. No fill dirt was brought in, only the lot soil used when graded for foundation building. These lots are minimum 10,000 sq ft so not huge but not small either by today’s new home standard or usual lot sizes. When we had our hardscape done for back yard, it included 1,100 sq ft of pavers so more dirt was moved around to create level paver bed. Our typical soil in this area is clay so we did have 3 way mix landscaping soil brought in when we began planting the wide bed between the pavers and fence & then it was topped off with truckloads of that great mulch which we dug in as we planted. So, that’s the long boring story of my back yard soil and also why my crop of mushrooms is such a mystery to me! They’re still out there though somewhat buried under hydrangea & maple leaves so we‘ll see if they’ve decomposed when my spring yard cleanup begins! Can’t wait!😊

The mushrooms are just indicators of an organic matter digesting fungus that is feeding off of whatever was in the 3-way mix and/or the mulch. Not at all unusual in our climate at this time of year and can appear well after the fact.......it takes time to break down all that OM!

Consider how long fresh mushrooms last in your frig..... couple weeks, maybe? Those shrooms will be long gone by spring!