Thank you for your question.  We apologize for our delay in responding to you.  Before doing that, however, we have two questions for you.  Have you and/or your neighbors cut down any trees within a distance of 20 feet or so from these pavers?  If so, how long ago and what kind of tree(s) were cut down.  Looking forward to your responses!

Just thought of one more question that arose in my mind as I was considering your question.  You said that this area is shady.  Specifically what kinds of trees do you have around the area?  Many thanks for your response.

Thanks for your question.

Mushrooms are not your problem. They have a shallow root system and their physical structure is such that they cannot exert upward pressure against the pavers. These mushrooms appear to be a type of Agaricus mushroom. They tend to appear in late summer and early fall. I strongly suspect that the upward movement of these pavers has been occurring for at least a few years. Perhaps you just did not notice it until the mushrooms caught your attention? Or, perhaps, this rising up of the pavers only became noticeable this season? Mushrooms such as these feed on decaying wood. My best guess is that under these pavers are roots of one or more trees. I have requested information from you about the presence of trees around these pavers but as this date have not heard from you. The fact that these pavers are in a shady area strongly suggests that trees are around. It could also be the case that within the last five years or so you have removed trees from your property. Roots from those trees could still be in the ground under your pavers. Depending upon the species of tree, roots can grow out 20 to 30 feet underground from a tree’s base. The mushrooms you are observing are – my best guess – feeding upon these roots. Given the recent weather in your area, these mushrooms are now dead. However as long as roots are beneath the pavers look for a reappearance of mushrooms next spring. If they do appear at that time, just take a rake and knock them over. Your bigger problem concerns the roots and pavers. If as I suspect that underlying roots are causing this upheaval, then your only recourse is to remove the pavers and dig down to the roots and remove them. However this approach is also fraught with problems. Removing large roots from a tree can compromise the health of that tree and could lead to its decline. If only a few pavers are involved, all things considered, your best course of action might be to just live with this situation. An intermediate course of action might be to lift up the affected pavers and remove the underlying gravel/sand base but not any roots. Perhaps this might bring the pavers back down to the height of the surrounding pavers?

Good Luck!!

Thanks for your recent response and pictures. On the basis of your new comments and pictures I would like to modify my initial comments as follows:

1). I agree that roots from adjacent trees may not be the problem. Upon close examination of your pictures, it seems as if the pavers are being raised at their edges and that the entire paver is not being raised. Roots growing upwards would be expected to push the whole paver upwards.

2). Given your recent pictures, my initial identification of these mushrooms as Agaricus is now less certain.

3). It appears that your pavers are laid on a rock base. If so, they may be more apt to move than if they were embedded in a sand base. It is conceivable that mushrooms growing through this rock base and up through the space between the pavers could elevate the paver edges.

4). That your patio may reside in a cleared wooden area certainly would suggest that the soil under the patio might have a high organic content. This is what the mushrooms are feeding upon. Digging them up by hand and disposing of them in plastic bags is an excellent way to proceed.

5). These mushrooms will continue to grow as long as organic material is in the soil under the pavers. There are few fungicides that will kill the mushrooms. If you want to go down this road, look for a fungicide containing azoxystrobin or flutolanil. These are not pleasant chemicals and should be applied by a professional lawn service individual. However such fungicides will not eliminate the organic material in the soil and mushrooms would probably return.

6). I now believe, and you alluded to this, that the best approach might be to hasten the decay of the organic materials in the soil under the pavers. This will not be a fast process and may necessitate efforts over a few years. So here’s the deal. Early next spring (2023) apply a nitrogen-rich fertilizer to the gravel between the pavers. Water it in well. Don’t use any slow-release formulations. This nitrogen will hasten the normal decay processes of organic material (e.g., roots) that may be in the underlying soil. Possible nitrogen-rich fertilizers would include ammonium sulfate or ammonium nitrate. Also look for commercial fertilizers and plant food that contain 24% nitrogen or higher. This number would appear on the product label of these fertilizers. Do this next spring. You may have to apply it more than once during 2023. To the extent possible avoid having these compounds, and any water running off of them, go onto the turf surrounding your patio.

Good luck with all of this. And certainly feel free to get to us with any questions that might arise.