It sort of looks like a coral reef, but not underwater.

June 21, 2020 10:27 AM

We are growing vegetables in raised boxes, and they happen to have a lot of these mushrooms growing in them. They look kind of cool, but a) what are they and b) should we be concerned about the vegetables (particularly the root ones)?

We are using raised boxes, which we started with a layer of (probably fresher than it should have been) horse manure (about 10cm deep) over which we put around 30cm of soil (which has settled quite a lot). We started noticing these mushrooms growing from many of the gaps between the wood, as well as directly up in the soil along the edges as you can see in the photo.

Questions are as above: What are these? Should we be worried about our plants, or be happy about a cool-looking visitor that is doing its part in the wonderful world of biodiversity?

(For the record, we are in the south of Sweden, in case that is relevant in identification)

posted by vernondalhart to Home & Garden (7 answers total)

It’s some sort of cup fungus. See here for further info on ID. They are usually saprobes that feed on decaying organic matter or symbiotes with plant roots. Some are often found at burned sites, maybe you mixed ash in your soil?
posted by SaltySalticid at 11:09 AM on June 21, 2020 [2 favorites]

Response by poster: We collected the soil from the communal composted soil pile. It is possible there is ash in there (we can usually see small wood bits), but I don't know exactly what is done in the composting process.
posted by vernondalhart at 12:48 PM on June 21, 2020

Best answer: This is not something to worry about. Healthy soil should have a wide variety of fungi living in it. Just don’t eat the mushrooms unless you actually know what they are.
posted by rockindata at 2:02 PM on June 21, 2020 [2 favorites]

Response by poster: So just to be clear, there should be no concern about eating root vegetables like beets that are growing in the same soil as these? Assuming we clean them, of course.
posted by vernondalhart at 2:05 PM on June 21, 2020

Best answer: No, sorry I was not more clear. They are not generally known as a plant pest or pathogen. They are likely not edible but they wouldn’t seem to be doing anything to your root vegetables other than growing nearby. I’m not sure what kind of problem you are envisioning but if your root vegetables look normal and healthy they, probably are. This is not a known cause for concern although I concede I am not an expert on fungal ID or plant/fungal relationships.
posted by SaltySalticid at 4:25 PM on June 21, 2020 [1 favorite]

For stuff like this, the Cooperative Extension Agency is a great resource.
posted by theora55 at 8:16 PM on June 21, 2020

A Peziza, perhaps (like the fittingly-named "compost cup"?).

Whatever it is, I presume it's feeding off of compost or wood chips in your soil and poses no threat to you or your beets.
posted by wreckingball at 12:23 PM on June 22, 2020