Marasmius oreades is known the world over as the fairy ring mushroom. I have not come upon them in the wild, though they do grow in Australia, having probably been imported from Europe. I came upon them in a market in Perth, where they were being sold for $160 per kilogram, imported from France! The picture below shows what they look like by the time they have been picked, shipped and packed. 
In France, these are known as Mousserons. Note. October 2012. After investigating further during my trip to France, it appears that Marasmius oreades is known as the Faux Mousseron. Mousseron is applied to Marasmius oreades by English speakers, while the French refer to Calocybe gambosa or St George’s mushroom as mousseron, or mousseron vrai. This muddies the waters somewhat as it is not easy to distinguish the identity of the dried specimens above. The way the stems split and their relative thickness would seem to be contrary to what one would expect from M. oreades. I will pick some in the morning and investigate this further. I will leave the reader to investigate further the identification of these mushrooms. This investigation should be undertaken with care, as there are lots of mushrooms that come up in fairy rings, and some of them are extremely poisonous. Here is a link describing them in Victoria. (I need to find a new link it seems) Update October 2012 Here is a picture of some of these mushrooms growing in France, in the village of Correze, which I am visiting to attend the annual mushroom festival. These are in the lawn of the place where I am staying. I will take one down to the fete tomorrow to have the identification verified.
Marasmius oreades growing in France
A couple of distinctive features of this mushroom are the dark raised central region of the cap, and the toughness of the stem, which can be twisted back on itself without breaking.
Twisted fairy
While I was in France, I was invited to visit a farm in the Alpes Maritimes, at an elevation of 1000m. Here I was shown M. oreades growing in classic fairy rings in an open paddock. The rings could be seen quite clearly by their dark green colour in comparison to the surrounding grass. The image below shows my host kneeling down to harvest some mushrooms from one of the rings.
Picking M. oreades from fairy ring.
See also my fellow blogger for further information
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Gibbo said,
July 3, 2013 @ 12:01 pm
I used to find these in the hundreds in the grass on the foreshore of Williamstown, Victoria. Quite tasty – I read years later that people were selling these as imports at that ridiculous price.
morrie2 said,
July 3, 2013 @ 2:54 pm
Hi Gibbo,
I have heard that they grow in Victoria. Perhaps they are being sold as imports in WA, but they are marketed as being from France. It would be a nice little earner 🙂
Morrie
Gibbo said,
September 24, 2013 @ 11:16 am
Was thinking about grabbing a few to culture them and see if I could grow them where I live now.
Edison said,
January 8, 2014 @ 3:25 am
Hello! I want to buy from Taiwan Marasmius oreades! Does anybody willing to help?
Jonathan said,
June 9, 2014 @ 10:03 am
Yes these are very common everywhere around Melbourne, usually fairly early on in the season. One thing that hasn’t been mentioned….the amazing smell that I have seen described as bitter-almonds/marzipan. Slightly disconcerting because cyanide is meant to be similar but be assured, these fungi are fine. The smell makes them absolutely diagnostic and once recognized, you will always be able to do so. Mind you, I will need to experiment with recipes to get the most out of them. For me, standard frying I felt could be improved. Maybe drying to use as a seasoning.
morrie2 said,
June 12, 2014 @ 2:03 pm
Thanks for those comments Jonathan. I have not previously been aware that there is an odour associated with these. I didn’t notice any in the specimens that I picked in France, though I was not looking for it. I have a couple of papers where people have done GCMS on this odour for Agaricus species and identified it as being due to benzaldehyde and benzyl alcohol. In some cases this can be a bit overpowering in Agaricus.
Cheers,
Morrie
Jonathan said,
June 21, 2014 @ 7:59 am
Well benzaldehyde would make complete sense – so I figure you are onto something there. The smell isn’t overpowering but definitely there. If you collect a few fresh and put in bag, then smell the air in the bag it should be quite noticeable….it would be interesting if those in Australia have this odour but those in France don’t!
By the way I found some delightful sturdy grey fungi that I cannot id but they smell delicious. It would be nice to know what they are! Can I upload a picture? (though after a week in the frig they are not exactly fresh)
morrie2 said,
June 21, 2014 @ 8:30 am
I checked with a European guide that I have and it does mention the odour.
If you want to post a picture, you can put it on photobucket or somewhere similar and post a link.