Over the years I have had a few of those button mushroom kits you see in the garden centre (I won’t be buying any more, because they contain peat, but that’s another story). They rarely fruit well, as if they enjoy the conditions indoors (which are not as controllable as they would like) then they suffer attack from fungus gnats. Inevitably they end up on the compost heap at some point.

Up until now, that has never obviously resulted in any button mushrooms growing outside, but now I think it may have. These are growing in one of my troughs:

Edible mushrooms?

Now that I’ve put them out of reach of slugs they can grow properly, and they look like button mushrooms to me. But I am not an expert on fungi, so I would like to be sure. What features am I looking for to identify these as edible (or not)?

I picked one of the ones that was slug-damaged. It was pretty young, but the gills look like this:

Gills

and this is the stem:

Stem

There’s no obvious staining when they’re damaged, and they smell nicely of mushroom. Any thoughts?