Agaricus osecanus – Giant horse mushroom, giant disappointment

cropped giant horse

I found this monster growing at the base of a eucalyptus tree in Bridgetown.  It was almost buried, rather like Agaricus bitorquis.  Although I have called it Agaricus osecanus, that is a fairly loose term, referring to a group of similar mushrooms. I am using Arora as a guide.

I first found these during Spring, and then again in Autumn.  The most distinctive feature of them is the huge diameter of the stem.   As you can see, it is a handful.   In fact the specimen above appears to be three individuals fused together and it had dried out a little and cracked so that it was in danger of falling apart.   The flesh however was quite firm.

I was quite excited when I found such a large mushroom that was clearly an Agaricus of some sort and therefore likely to be edible.   I thought that I would take a culture of it as soon as a I could.   However, the smell was not like any other member of the genus that I have ever encountered.   A friend described it as ‘earthy’ but I found it simply ‘less than attractive’.

Before going to the trouble of culturing it, I decided to do a small taste test.  To this end, I cut some small slices (no colour change) and fried them in a little butter/oil.   My friend and I both tasted it and though the initial taste seemed ok, we had both spat it out within 5 seconds.   It tasted terrible.  Hard to describe exactly, but I found it to have a floury taste.  Certainly not something that you would want to swallow.

So, for me this represents a fourth grouping within Agaricus, based mainly on the smell.  The other three categories are mushroom (octenol) smell, almond smell and phenol smell.  I can’t put a description to this smell, but it does not fit into any of the other three categories.   `

Such a shame.  It was massive and had lovely white firm flesh.

Ah well.

Note: May 2016

I had hoped to get another specimen of this and send it off for dna testing, but this year someone came along and not only smashed them up, but ripped off all the loose bark of the tree whose base it was growing at.  Such a senseless act and now we may never know what this was.


5 Responses so far »

  1. 1

    Glenda said,

    Hi Morrie. You have got me thinking I should check out my Baileyana and see if there are any mushrooms there this year. There may not be as the tree is looking pretty sick. Good to know this one is not so tasty.

  2. 2

    morrie2 said,

    Hi Glenda. If you got the same big downpour that we did here last night then it might be worth a look.
    I still have your charcoal and we must do that dinner. Time seems to have slipped away so fast..

  3. 3

    hi morrie, great site. today i found some mushrooms that looked like the regular field ones I collect (and eat) from our vineyard. but on closer inspection, they were not exactly the same as i hope the photo link here shows you. the tops have a reddish tinge, and although the mature samples had dark gills, the juvenile ones were pale, yellowish. any idea what they might be? Not planning on eating them, just so you know ;
    the suspicious ones are on the bottom of the pic…the 3 at the top are the edible ones I ate tonight.

    • 4

      morrie2 said,

      Hi there,
      Thanks for your comments.
      Both of those look like Agaricus to me. Sometimes a reddish top can mean that they are the inedible ones with a phenolic taste. You should be able to detect that. Some of them do start with white gills. The important thing is that they end up dark brown. And that they pass the other tests like the cap breaking off from the stem.

  4. 5

    Thanks heaps!

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