Agaricus arvensis – almond mushroom

At various times of year, including mid summer, the parks around Perth erupt in large amounts of mushrooms.  These grow in circles that can be 10 or more metres in diameter.

Viewed up close, the mushrooms have a distinctive appearance.

These mushrooms have a smell of almonds that varies in intensity, depending on the location.   Some smell so stongly of almonds that they can only be used as a flavouring.  The almond smell is due to the presence of benzaldehyde.  This has been shown by gas chromatography.

These mushrooms are white gilled initially and then the gills turn to dark brown with age.   They also bruise yellow, which is often taken as a sign of inedibility.   In fact, however, the yellow staining mushrooms that must be avoided are Agaricus xanthodermus and other species  which contain phenol.    To be able to eat these mushrooms with confidence, one needs to be able to distinguish between the smell of phenol and the smell of benzaldehyde.   That is the smell of phenyl disinfectant and the smell of almond essence.

I find that the small mushrooms are the best to eat.   I have seen other people collecting these.   Some elderly Italian gentlemen.   I have also grown this mushroom.  Well, just one small one!

Here is a picture of a small one, taken in Dagleish, Perth, on 29 March 2010.

In fact, these were the first mushrooms to be put into cultivation, before the normal Agaricus bisporus, and if the early attempts at cultivation had turned out differently, we might be used to the taste of almond mushrooms.

Since these mushrooms grow in the open sunlight, it is interesting to speculate whether they contain significant quantities of vitamin D, since the development of this vitamin has been demonstrated in other members of the genus when exposed to ultraviolet light, as described in this slide presentation.

Here is a few that I picked one lunchtime that are sitting on my keyboard in my former office in Perth.

Agaricus xanthodermus, the one that has the phenolic smell, is not something that I have encountered often.   I did come across this bunch of them growing in sand at Yeagarup though on 5 May 2007.  The smell was very distinctive as was the yellow colour of the base of the stem.  The yellow colour is due to a the oxidation of the phenolic group of leucoagaricone to form agaricone, by atmospheric oxygen.

One last comment.  These mushrooms only have white gills at the immature stage.  One should be very careful to ensure that the gills turn brown with age.  Never eat a mushroom with white gills in the belief that it is a field mushroom unless you have established that you are looking at the immature stage of an Agaricus.   That will take some experience.  Failure to heed this advise could be fatal!

Mature specimens of Agaricus never have white gills.  The deadly Amanitas do.

6 Responses so far »

  1. 1

    ref said,

    Thanks for the great info. Benzaldehyde smells like cherries to me and I don’t enjoy the taste of mushrooms but my wife smells almonds and loves them. Maybe there’s a link.

    • 2

      morrie2 said,

      Hi,

      Thanks for you comments. I had not heard of the cherry/almond connection before, but a bit of searching reveals that many people smell cherries where others smell almonds. Smell is quite a subtle thing!

      Morrie

  2. 3

    sunny said,

    I recently spotted a very large cluster of what appeared to be Agaricus Arvensis in my local park. I took photos, samples, spore prints etc but some sites say spore print should be brown, but mine were pale white. Stem was light brown, not white as per pictures I’ve found. Flesh and stem of mine turned rusty brown in a few seconds after being cut, but didnt’ stain yellow was probably was not Agaricus Xanthodermus. Apart from that, seems a match….. what do you think?

    • 4

      morrie2 said,

      If the spore print is not brown, then it is NOT an Agaricus. There are no exceptions to this. Do not eat these under any circumstances.

      Please read my description of how to identify a field mushroom.

      • 5

        sunn said,

        Thanks for the feedback. So far, it looks like it might be Chlorophyllum Molybdites, which is definitely not edible. I’ve not seen such a large, dense cluster of them before. There were 80+ bodies up to 15cm diameter in a 4 sq metre area.

      • 6

        morrie2 said,

        I have had contact with a few people who have found large quantities of mushrooms that sound similar to these. One sample I saw turned out to be Macrolepiota brunneum. I thought that I had written it up, but I seem to have overlooked it. I have also seen large quantities of C. molybdites growing in a confined area.

        There is a key here which may help, http://nature.berkeley.edu/brunslab/papers/vellinga2003_aust.pdf

        Cheers,

        Morrie


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