Identifying a field mushroom

Disclaimer  :  These notes are provided as a guide only.  While every attempt has been made to try to assist in the identification, the risk of eating any wild mushroom rests with the individual and I do not accept  any responsibility for consequences  that may arise from the action of anyone eating wild mushrooms.  See also  inedibles and lookalikes

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The fungus that we know in Australia as a field mushroom is a member of the genus Agaricus.  This is a large genus with a single ancestor (monophyletic) and within the genus is a number of sections each containing a range of species.  While it is tempting to try to assign a species name to any mushroom that you might find, this can be difficult in Australia because many of the species are undescribed or if they are described they aren’t reported in popular guide books.  In addition, it might require the use of a microscope and other detailed analysis.   For our purposes though, it isn’t important to have a name; edibility can be determined by features that can be simply observed.  Our main objectives are:

  • make sure we have an Agaricus
  • Make sure it is not in the section Xanthodermatei

Examples of some well known members of the Agaricus genus are:

Agaricus bisporus – the classic small supermarket mushroom

Agaricus bitorquis – marketed as a larger form of supermarket mushroom

Agaricus arvensis – the almond mushroom or horse mushroom.

Agaricus campestris – the classic if oft mis-identified field mushroom.

This list of features has been put together to assist the average person to identify an edible field mushroom.

1.  Cap colour and texture

The cap of the edible Agaricus species varies from white though dun and on to a slightly pinkish colour in species like A.  sylvaticus.  The cap may be slightly scaley, and may be cracked.  It is always dry and is never slimy to the touch.  Both the colour and texture of the cap are influenced by the environmental conditions as well as the genetics.

Any mushroom with any hint of green in the cap colour should be rejected as this is the colour of the deadly Amanita phalloides.

 top of small field mushroom, typical of those found in lawns (Dave Freer)

top of large field mushroom, similar to supermarket field mushroom (Dave Freer)

top of Agaricus arvenis, showing scales

A forest mushroom, showing red tones on the top

Top of Agaricus bitorquis.  A clean off-white, with undulations

A horse mushroom from the Riverina district of NSW.  Note scales.

A mushroom from a backyard in Penshurst, Victoria, showing some radiating spots.

A mushroom from Digby in Victoria, showing red/brown central region and radiating scales.

2.  Gill colour

The gill colour may vary from brown to pink or off-white in the young mushroom, but it will always darken to a dark brown in a mature specimen.  ‘Not black, but dark brown. Never eat a ‘field’ mushroom with white gills.  This eliminates the poisonous Amanita and Chlorophyllum molybdites.

Pink colour of immature specimen of  a small field mushroom.  Picture courtesy of Dave Freer.

 

3.  Spore print

The spore print is always dark brown.  Not pink, not rusty, not black or purple or white.  Dark brown only.

How do we take a spore print?  Easy.  Place the mushroom, or a piece of it, on a piece of waxed paper and place a glass over the top, with the edge of the jar just propped up by a matchstick or something similar to allow water vapour to escape.  Place in a position away from draughts, overnight.

A simple setup for taking spore print

A spore print of an Agaricus species

4.  The stem snaps away from the cap

The stem of an Agaricus has a texture that comprises a bundle of stringy cells running axially.  The cap has a different texture.  At the point of the junction of these two textures, there is  region where the two will break apart cleanly.  Try this for yourself with a supermarket mushroom.  Note in this mushroom the dark gill colour.

The point of separation should be between the top of the stem and the flesh of the cap.  In some species the stem appears to break away cleanly, but close inspection will show that there is a piece of the flesh from the cap attached to the stem and the position of the separation is actually between the surface of the cap and the flesh of the cap.

This test serves to separate Agaricus from members of the family Cortinaraceae, such as Hebeloma, Inocybe, Cortinarius and Galerina, some of which are seriously poisonous.  It does not separate it from Amanita though.

5.  Smell

Field mushrooms have a distinctive smell that is either ‘mushroomy’  due to a chemical called octenal, or almond/aniseed due to the presence of benzyl alcohol and benzaldehyde.

If the mushroom has a smell of phenol, which is the smell of India ink, or phenyl disinfectant, coal tar soap, creosote or sometimes described as ‘chemical’, then it should be rejected.  Another common product that has the phenol smell is wheelie bin cleaner.  It contains cresols, which are related and smell the same.   Interestingly, and I don’t know why, at high dilutions wheelie bin cleaner smells like Clag glue. Perhaps they use phenol as a preservative.

If in doubt,  there are three approaches you can take;  1) put the mushroom in a plastic bag for 15 minutes and then sniff the contents or  2) heat a piece of the suspect mushroom in a microwave for a minute.  3) Keep one on your desk or other work surface for a few hours.  Sometimes when the smell is not apparent at first it will become apparent over time.  I don’t know what is behind this effect.  The bad smell will become more apparent if there is phenol present as will the almond smell. If you can’t reliably and comfortably identify the smell, preferably with confirmation from someone else, then you should reject the mushroom.

It is often reported that some people can tolerate eating mushrooms that contain phenol.  I did not believe this for a long time but a friend showed me a specimen of what was undoubtedly a yellow staining mushroom from Section Xanthodermatei that a local farming family had been consuming without ill effect.  The identity was confirmed by DNA analysis.  Like many poisons, there is a distribution of susceptibilities in any population and this seems to be an example of that.

Why is phenol a problem and benzaldehyde isn’t?   Because phenol causes acute irritation of the gastrointestinal tract.  This can cause distress and vomiting, but it will pass and will not leave any permanent damage.  Benzaldehyde is a natural product that is a component of almond essence that is used in making marzipan and is without any toxic effects at the doses involved in mushroom consumption. Similarly, benzyl alcohol has low toxicity.

Some poisonous species contain hydroquinone as well as phenol.  This too can also cause gastric upsets. In these ones, both the phenol smell and the yellow colour are not as intense.  The smell should be determined on a fresh specimen at the base of the stem.

6.  Colour of cut or bruised flesh

The colour of the cut or bruised flesh may be brown or red or yellow, or there may be no change in colour at all.  Here for example is an edible mushroom, Agaricus bitorquis, which is showing red on a cut piece.  Photo courtesy of Dave Freer.

Brown or red bruising is usually ok but not an infallible indicator.   A yellow colour may be ok or it may indicate Agaricus xanthodermis, which will cause stomach upsets.  There is much confusion about this.  The yellow colour is an indicator of  A. xanthodermus, which contains phenol, but it does not necessarily indicate an indedible mushroom.   For a diagnosis of an indedible yellow staining mushroom, one needs to have the yellow stain in combination with a phenol smell, as mentioned above. Another term for yellow staining is ‘flavescent’.

The place to determine both the colour and the smell is the base of the stem.  Both features are less prominent in other regions of the mushroom. Don’t be shy, really squash it to get the smell.

Another feature of the yellow staining inedible species is that the yellow colour changes to brown over about an hour.  The yellow colour also intensifies with cooking.  Another test is that the colour intensifies and stays permanent in response to a drop of a 10% solution of potassium hydroxide or the more easily obtained sodium hydroxide which does the same thing. Below is a picture of a mushroom that has been tested with sodium hydroxide.  For some more details on structure and staining in section Xanthodermatei, look here.
yellow stain with caustic

7. Substrate

Field mushrooms will always be found growing from some kind of soil.   They never grow directly from wood and they do not  grow in the middle of cow pats.  There are some deadly species like Galerina that grow from wood and if it is growing from a cow pat, there is a good chance that it is the notorious hallucinogenic ‘gold top’, on the Australian east coast at least.  They do not tend to grow from wood chip or bark mulch either.

Don’t pick and eat mushrooms that grow beside highways or other places where they may have accumulated things like heavy metals or other potentially toxic things.  Mushrooms can be quite good at gathering these things.

8.  Cap shape

Mushrooms of the Section Xanthodermatei, the yellow-staining, phenol containing species tend to have a flat top when juvenile, sometimes continuing to when they are fully grown.  They are often described as having a ‘boxy’ shape.

This, however is not exclusive to this section.  There are many other species that have a similar flat top, and the classic example is Agaricus augustus, known in the US in particular as The Prince, and highly prized as an edible.  So the flat top has limited value as a diagnostic tool.  Sometimes people declare mushrooms to be yellow strainers and therefore inedible based on shape alone without even testing for a yellow stain and smell.  I suggest taking a more thorough approach as outlined above.

9. Tasting

If you are eating an Agaricus that you have never eaten before, try out a small piece first. Sometimes we can be allergic to mushrooms for no apparent reason.   If it tastes horrible, don’t eat it!  This has happened to me with something I expected to taste good.   If you have not experienced any ill effects by the next day, then you can move forward to eating a larger quantity.

Whatever you do, don’t gulp down a huge meal of something that you are unfamiliar with.

10.  One final thing

If, after reading all of the above, you are still not sure, then there is an old mushroom gatherers maxim that applies:

If in doubt – chuck it out

(This picture is repeated as a Facebook catcher)

agricarus 4

Peter Donecker

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Growing your own mushrooms – A Miller’s tale

Cultivation of the common field mushroom began in France in around 1650. The technique was transferred to England when detailed instructions were published in The Gardener’s Dictionary, first published in 1731 by Philip Miller. That’s him in the picture above, somewhat enhanced by modern photo editing techniques. Quite an accomplished man, he was a Fellow of the Royal Society.

It seems that this was quite a popular pursuit in the day and that the technique may have been introduced into Australia with the first English settlers. In the Swan River Colony of Western Australia, which was first settled in 1829, there is a comment made by James Drummond in 1845 that the common field mushroom has become established in the colony following its cultivation. It is likely that the species cultivated reflect what was growing wild in England at the time.

People often ask in online forums if it is possible to grow mushrooms from wild ones that occur in their lawns etc. This method details a technique for doing exactly that.

The book is available online as a PDF download courtesy of Google. I have taken that PDF and used OCRbest to extract the information in text form. It did a very good job. In those days an ‘s’ looked rather like an ‘f’ so I have had to weed out those occurrences. I hope that I got them all. I have made some minor edits to allow the text to be broken up into shorter paragraphs. Anyway, I reproduce his method below. Good luck to anyone who wants to try it.

Philip Miller’s Mushroom Growing Method

MUSHROOMS are, by many persons, supposed to be produced from the putrefaction of the dung, earth, etc. in which they are found ; but notwithstanding this notion is pretty generally received amongst the unthinking part of mankind, yet by the curious naturalists, they are esteemed perfect plants, though their flowers and seeds have not as yet been perfectly discovered. But since they may, and are annually propagated by the gardeners near London, and are (the esculent form of them) greatly esteemed by most curious palaces, I shall briefly set down the method practised by the gardeners who cultivate them for sale. But first, it will not be improper to give a short description of the true eatable kind, since there are several unwholesome sorts, which have been by unskilful persons gathered for the table.

The true Champignon, or Mushroom, appears at first of a roundish form, like a button; the upper part of which, as also the stalk, is very white; but being opened, the under part is of a livid flesh colour, but the fleshy part when broken is very white ; when these are suffered to remain undisturbed, they will grow to a large size, and explicate themselves almost to a flatness, and the red part underneath will change to a dark colour.

In order to cultivate them, if you have no beds in your own, or in neighbouring gardens, which produce them, you should look abroad in rich pastures, during the months of August and September, until you find them (that being the season when they are naturally produced then you should open the ground about the roots of the Mushrooms, where you will find the earth, very often, full of small white knobs, which are the offsets, or young Mushrooms; these should be carefully gathered, preserving them in lumps with the earth about them : but as this spawn cannot be found in the pasture, except at the season when the Mushrooms are naturally produced, you may probably find some in old dunghills, especially where there has been much litter amongst it, and the wet hath not penetrated it to rot it.

Likewise, by searching old hot-beds, it may be often found; for this spawn has the appearance of a white mould, shooting out in long strings, by which it may be easily known wherever it is met with : or this may be procured by mixing some long dung from the stable, which has not been thrown on a heap to ferment; which being mixed with strong earth, and put under cover to prevent wet getting to it, the more the air is excluded from it, the sooner the spawn will appear; but this must not be laid so close together as to heat, for that will destroy the spawn : in about two months after the spawn will appear, especially if the heap is closely covered with old thatch, or such litter as hath lain long abroad, so as not to ferment, then the beds may be prepared to receive the spawn.

These beds should be made of dung, in which there is good store of litter, but this should not be thrown on a heap to ferment; that dung which hath lain spread abroad for a month or longer, is best. These beds should be made on dry ground, and the dung laid upon the surface; the width of these beds at bottom should be about two feet and a half or three feet, the length in proportion to the quantity of Mushrooms desired; then lay the dig about a foot thick, covering it about four inches with strong earth. Upon this lay more dung, about. ten inches thick; then another layer of earth, narrowing in the sides of the bed, so as to form it like the ridge of a house, which may be done by three layers of dung and as many of earth.

When the bed is finished it should be covered with litter or old thatch, to keep out wet, as also to prevent its drying; in this situation it may remain eight or ten days, by which time the bed will be in a proper temperature of warmth to receive the spawn; for there should be only a moderate warmth in it, great heat destroying the spawn, as will also wet; therefore when the spawn is found, it should always be kept dry until it is used, for the drier it is, the better it will take in the bed; for I had a parcel of this spawn, which had lain near the oven of a stove upward of four months, and was become so dry, that I despaired of its success; but I never have yet seen any which produced so soon, nor in so great quantity as this.

The bed being in a proper temperature for the spawn, the covering of litter should be taken off, and the sides of the bed smoothed; then a covering of light rich earth about an inch thick should be laid all over the bed, but this should not be wet ; upon this the spawn should be thrust, laying the lumps four or five inches asunder ; then gently cover this with the same light earth above half an inch thick, and put the covering of litter over the bed, laying it so thick as to keep out wet and prevent the bed from drying! when these beds are made in the spring or autumn, as the weather is in those reasons temperate, so the spawn will then take much sooner, and the Mushrooms will appear perhaps in a month after making; but those beds which are made in summer, when the season is hot, or in winter, when the weather is cold, are much longer before they produce.

The great skill in managing of these beds is, that of keeping them in a proper temperature of moisture, never suffering them to receive too much wet: during the summer season the beds may be uncovered, to receive gentle showers of rain at proper times, and in long dry seasons the beds Should be now and then gently watered, but by no means suffer much wet to come to them ; during the winter season they must be kept as dry as possible, and so closely covered as to keep out cold.” In frosty or very cold weather, if some warm litter shaken out of a dung heap is laid on, it will promote the growth of the Mushrooms; but this must not be laid next the bed, but a covering of dry litter between the bed and this warm litter ; and as often as the litter is found to decay, it should be renewed with fresh; and as the cold increases, the covering should be laid so much thicker. If these things are observed, there may be plenty of Mushrooms produced all the year, and these produced in beds, are much better for the table than any of those which are gathered in the fields.

A bed thus managed, if the spawn takes kindly, will continue good for several months, and produce great quantities of Mushrooms; from these beds when they are destroyed, you should take the spawn for a fresh supply, which may be laid up in a dry place until the proper season of using it, which should not be sooner than five or six weeks, that the spawn may have time to dry before it is put into the bed, otherwise it will not succeed well.

 Sometimes it happens, that beds thus made do not produce any Mushrooms till they have lain five or six months, so that these beds should not be destroyed, though they should not at first answer expectation; for I have frequently known these to have produced great quantities of Mushrooms afterward and have continued a long time in perfection.

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Leucocoprinus birnbaumii – the flowerpot mushoom

One of the most commonly asked questions on mushroom forums is “What is this yellow mushroom in my flowerpot”. The mushroom they are referring to is Leucocoprinus birnbaumii. This is one of a number of closely related species that are associated with potting mixes.

It is a fleeting mushroom, appearing as a small yellow lump then growing into a small parasol shape before sinking back into the substrate. Part of this process is caught in the video below, reproduced with kind permission of Thomas Phoon Kong Wai of Singapore.

This mushroom was first described by British mycologist James Bolton in his book ‘A History of Fungusses growing about Halifax‘ published in 1788. He gave it both a common name, ‘Yellow Cottony Agaric’ and a botanical name, Agaricus luteus, seen on the left.

Unfortunately, the name he gave it, Agaricus luteus was already in use so his nomenclature did not fit with the rules and it fell to Czech mycologist Augustus Corda who found it growing in a greenhouse in Prague to name it after a garden inspector called Birnbaum.

I was rather intrigued by the note that Bolton made regarding it being found in a pine-stove. I had no idea what a pine stove was but further investigation reveals that the growing of pineapples was all the rage in England and Scotland at the time and wealthy people constructed hothouses with elaborate heating systems in which to cultivate them in the cold climate. One elaborate monument to this fad is this construction by John Murray, the 4th Earl of Dunmore which you can visit in Scotland.

Chemistry

The intense yellow colour of these mushrooms is due to two alkaloids known as birnbaums.

The structure of these compounds was determined by Bartsch et al. in 2005. This work is in some places referenced with the comment that these compounds are toxic but if one reads the paper there is no such mention of toxicity. A review by Rani and Granchi in 2015 also notes that there is no biological assessment of these compounds.

In fact this mushroom is widely described as toxic but the reality is that there is no data available anywhere to support this claim. Considering that this is such a common mushroom, one might expect some records of toxic effects to be recorded but there is nothing. Given that these are often found in indoor settings, they are the sort of things that pets might occasionally nibble on and in fact I noticed one such case on the Emergency Identification for Plants and Fungi page on Facebook. In this case a dog in Australia had eaten one. Inquiries with the vet revealed however that there was no indication of the dog suffering from toxic effects.

I think that this is one of those cases of the propagation of mushroom myths like the old chestnut about Coprinus comatus being poisonous if consumed with alcohol. It probably has its origins in the fact that this mushroom was at one stage grouped with the Lepiotas which do contain species that are deadly poisonous. I think that consumption of a small mushroom like this would be pointless and I would not recommend it but one member of a group I admin reported that he had eaten them.

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A missing Western Australian ‘Death Cap’ Amanita?

I was interested to read about some people in Rwanda who eat large quantities of a mushroom from the genus Amanita that grow in the Eucalyptus plantations there. This mushroom is called Amanita bweyeyensis. There is a YouTube video on the subject, from which this image is clipped.

Peeling Amanita bweyeyensis before consumption


https://www.youtube.com/watch?v=PtjRvTmg3GY

This mushroom sits within the Phalloideae section of Amanita, where the deadly species containing amatoxins reside. Despite this, it does not contain amatoxins nor phallotoxins. It is the amatoxins that are the cause of many fatalities when people eat other mushrooms in this section such as Amanita phalloides. Phallotoxins are not orally active so pose less of a threat.

DNA analysis shows that this mushroom sits within a small cluster that includes the white “death cap” mushrooms from Western Australia. These are: A. djarilmari, A. eucalypti, A. gardneri and A. marmorata. The partial phylogenetic tree is from this paper: https://mycokeys.pensoft.net/article/34560/zoom/fig/11/

Analysis of the Western Australian species has shown that these do not contain amatoxins either. This is reported in a paper that is behind a paywall but the precis is shown at this link.

This is a picture of the Amanita bweyeyensis from the paper mentioned above. Unfortunately, I can’t show pictures of the Western Australian species.


Since the African species sit so close to the WA species in terms of genetics and they grow in Eucalyptus plantations, it is tempting to think that they might have their origins in WA. If this is the case, they do not seem to have been recorded here. It is hard to know where the Eucalyptus trees planted in Rwanda came from originally; they are not WA natives but it is not beyond the realms of possibility that they came from Western Australia, given that this is the closest state to Africa.

This brings to mind the green Russulas that grow in the Eucalypt plantations in Madagascar which are eaten by the people there. They also peel those mushrooms before consumption. These Russulas are unknown in Australia though it would seem likely that is their origin.

How are amatoxins produced?

The production of amatoxins has been investigated in some detail by Heather Hallen and others in terms of genes. It has been shown that the amatoxins originate from proproteins synthesised on the ribosome. The function of the ribosome is shown in this rather cute image which is by SITNBoston and is taken from the Harvard University Site.

The codon carried on the mRNA (we all know what this is these days!) is decoded in the ribosome and amino acids carried by tRNA are converted into an amino acid chain which is known as a proprotein. This is similar to the process by which the covid spike proteins are produced by the mRNA vaccines.

These proproteins have a size in the range of 34 to 35 amino acids whereas the toxins have a size of 8 amino acids. In order for the amatoxins to be produced, these long chains need to be reduced in size and the fragments cyclised. This process has been studied in the amatoxin-producing genus Galerina by a group of researchers and the process is shown in this image from that publication.


The proproteins are acted on by the prolyl oligopeptidase enzyme which cuts the chain at the Proline amino acid and then stitches together the piece that is clipped out to form the bicyclic polypeptides (2 rings of amino acids) that we know as amatoxins.

The amatoxins are bicyclic (=two rings) octapeptides (=contain 8 peptides) with C-to-N (head-to-tail) condensation of the peptide backbone and a cross-bridge between Tryptamine(Trp) and Cisteine (Cys). Three of the amino acids (Trp, Pro, and Ile) are hydroxylated. Phallotoxins are similar in structure but their macrocycles comprise only seven amino acids. The relationship between the different amino acids is shown more clearly in this labelled diagram.

The image below shows a 3D view of an amatoxinA molecule in a similar orientation to the image above. The yellow sulfur atom can be seen within the structure and the 5-membered nitrogen-containing hetercyclic ring of (hyroxylated) Proline (P) seen on the left hand side with the (hydroxylated) Isoeucine (I) skeleton above it and Asparagine(N) below it. There is also a bridge with the (hyroxylated) Tryptamine sitting in the middle of the structure which is facing out into the page.

Amatoxin A molecule

This type of structure is very stable and survives heating and the action of digestive enzymes. That is one of the reasons that this type of toxin is so dangerous.

Just why this group of mushrooms does not always produce these toxins doesn’t seem to be well understood. I believe that specimens of Amanita marmorata taken from the same region i Hawaii have tested positive in one case and negative in another.

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In search of Woorda

There is not a lot of information around on the fungi eaten by indigenous people in Australia before the arrival of Europeans. One of the few references on the topic is by James Drummond who arrived in the Swan River Colony in the year it was founded, 1829.

James Drummond with grandchild

He was a botanist and a keen observer and recorder of the local flora as well as the diet of the original inhabitants. The following is a snippet from a letter he wrote to the Perth Enquirer in May 1842.

I have often wondered if it might be possible to identify the blue staining bolete that he describes as Woorda. There are many blue staining boletes in Western Australia and I know of several that people have eaten but none of them fit the description he gives. I had long suspected that it might be a Gyroporus since members of that genus are eaten elsewhere on the globe and with one exception they appear to all be edible.

A paper published in 2019 gives us some some useful information about Gyroporus in Australia. It is titled “Three New Species of Gyroporus (Boletales, Basidiomycota) from Australia”. In it is a description of Gyroporus occidentalis with an explanation that it is the only rapidly blue staining member of the genus from WA.

I was fortunate enough to spot one of these on a friend’s property this year and it is shown in the following video and photographs. It is recorded as growing from sandy soil (well, that’s most of the coastal plain!) and it’s range includes Perth. I think that there is a some chance that this is Woorda but see below for further possibilities.

The rapid blueing reaction in real time
In situ view showing cap surface and pores
View showing stipe and pore surface

Some of the features of this mushroom match the description in the paper closely. The cap is described as “dry, floccose to matted woolly to heavily appressed tomentose, yellow-white to yellow buff to dirty yellow, cyanescent, with slightly extended margin”. This close-up of the cap surface seems to match that description. I couldn’s see that the cap margin was extended though.

Cap surface

The pores are yellow and cyanescent and approximately 0.3mm in diameter with a typically pentagonal outline.

Anther interesting aspect of this is the name Woorda. Of course transcriptions of language are subject to errors and interpretations and so forth but the records of Daisy Bates provide for some interesting reading. These are available in digital form here. The many words recorded as meaning mushroom are provided on the site as a map. shown below. It triggers the question of whether the diversity of names matches the diversity of species that were part of the diet.

Map of words for mushroom from digital Daisy Bates site

The term Woorda appears in a dictionary of Balardong Noongar language as meaning fungus. It is difficult to know if this is a generic word or refers to the specific fungus that Drummond mentions. He does seem to infer that it is specific. It is notable that, at the time he wrote to the Enquirer, he had been farming at Toodjay (Duidgee) which is in Balardong country. That would imply that the range of the fungus includes Balardong country. I am not sure if Gyroporus occidentalis extends out this far but it will be interesting to find out.

Noongar groups. Attribute John D. Croft, English Wikipedia

The situation is complicated by the fact that there are other, rather similar looking blue staining boletes within Balardong country. One of these is documented by Doug Sawkins in his excellent record of the fungi of Foxes Lair at Narrogin. His very large blue staining bolete is similar in some ways to Gyroporus occidentalis but it lacks the chambered stem and has red tones where it has been attacked but insects. It matches one of Daisy Bates’ records of Woorda meaning ‘large mushroom’.

It is interesting to note that there is another record of the consumption of blue-staining boletes, in this case from Gippsland in Victoria It was made by the Silesian naturalist Lothar Becker who visited Australia in two trips in the period 1849-1865. This record is reported in a paper by May and Darragh in Historical Records of Australian Science, 2019, 30, 130-137, titled “The significance of mycological contributions by Lother Becker”.. A snippet from this is reproduced below.

Once again there is no information to identify this mushroom and there are many boletes that share this blue-staining property. I am not sure if there are any species that are common to Gippsland and Western Australia. We can rule out Phlebopus from Drummond’s comments and in any case they don’t always display blue staining. From time to time people report eating blue-staining mushrooms from various locations in Australia but sadly there is scant information regarding the actual identity of them. In some cases they have been eaten by people of European origin who have perhaps mistaken them for species from their home region. In one case in Western Australia consumption is recorded in a YouTube video and it was on the basis that boletes are generally non-toxic. This assumption has some statistical support but it remains the case that one of the few cases of fatal mushroom poisoning in Australia was from consumption of a bolete.

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Macrolepiota dolichaula – one of the best of the edibles

Macrolepiota dolichaula in its typical habitat – a grassy paddock (Image credit: Pixie Miller)

Macrolepiota dolichaula is a large mushroom that can often be seen in open paddocks from some distance away. It occurs in the warmer regions of Australia such as the North Coast of New South Wales and Queensland. It also occurs in other countries such as Vietnam, Northern Thailand and China. In all those places it is also considered an edible species. Genetically, the specimens from Australia form a monophyletic clade with the species from China. DNA Barcoding shows a 100% match between specimens from Australia and China. This is shown by specimens lodged by the mycologist who specialises in this genus, Else Vellinga. Genetically, it sits close to Macroplepiota procera, with which it is often confused.

Phylogenetic relationships in Macrolepiota, from :

When it is young, the mushroom has is bell-shaped (campulinate) as shown in the image below.

Young specimen of M. dolichaula shown bell-like shape (Image credit: Pixie Miller)

The centre of the mushroom has a slightly raised area (an umbo) which often has a light tan colour. From the centre, the cap squamules radiate towards the rim, the spacing getting wider towards the outside. These are white to very faint yellow-brown. The whole cap at maturity is between 60 and 160 mm in diameter.

Cap of M. dolichaula showing radiating squamules.(Image credit Drew Raison)

The gills are white to begin with, but darken to a straw colour over time. They are crowded and are not attached to the stem (free) and the length alternates between long (lamellae) and short (lamellulae).

Gills of M. dolichaula are white at first but become cream coloured over time. (Image credit: Drew Raison)
M. dolichaula, showing alternating long (lamellae) and short (lamellulae) gills (Credit: Jye Zap)

As the cap expands, a partial veil extending from the edge of the cap to the stem breaks away. This membrane has a similar texture to the cap surface. At the edges of the cap, ragged remnants of this partial veil remain.

Expanded cap of M. dolichaula showing partial veil breaking away. (Image credit: Simone Small)

If it is not torn away completely, as in the above image, on the stem, the remains of the partial veil form a ring or annulus. This hangs downwards.

Annulus on M. dolichaula (Image credit: Pixie Miller)

The stem (stipe) of the mushroom is often lightly covered with squamules rather like the cap. It tapers slightly from the base to the top and it is hollow. At the bottom of the stem, when cut or bruised will develop an orange/brown colour. It does not produce a bright red colour and does not form a colour at the top of the stem. The stipe also splits into vertical pieces. This can be seen starting to happen on the last picture at the bottom of this post.

People sometimes refer to these mushrooms as Parasols, or White Parasols but i prefer to avoid terms like this as they can lead to much confusion.

This mushroom needs to be distinguished from Chlorophyllum molybdites. With practice this is easy to do but for the beginner, the simplest test is to wait until a specimen matures and the gills of C. molybdites will be seen to develop a dark grey/green colour.

It also needs to be distinguished from Chlorophyllum hortense, a mushroom with smaller stature but similar appearance. This distinction can be made by the fact that Chlorophyllum hortense stains bright red immediately right through the whole length of the stem. Another feature that is less clear is that C. hortense has a striate margin, that is to say closely spaced lines at the edge of the cap.

In a book recently published by the CSIRO this species is listed as poisonous because of unspecified reports of bad reactions. Given that this mushroom is so easily confused with Chlorophyllum molybdites, I am confident that this mis-identification is the origin of such reports.

Within the Australian mushrooming community (not to mention China and Asia) this is regarded as one of the most popular and tasty of wild mushrooms. I am not aware of a single report of ill effects but I am aware of dozens of glowing reports regarding the edibility and taste.

M. dolichaula, picked and ready for the kitchen. (Image credit: Jye Zap)

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Anatomy of a Yellow Stainer

Within the genus Agaricus, the Section Xathodermatei contains a number of species that are commonly known as yellow stainers and they are known to contain phenol which causes quite nasty gastric upsets if consumed. I have been meaning to put together a post about these but it was only this morning that I found a substantial patch of them on a street  verge to do some images and experiments.  A few members of the patch are shown in the picture below.

Yellow stainers on street verge

 

The yellow staining reaction is seen both on the cap and on the stem of the mushrooms and manifests itself as a bright chrome yellow stain that quickly fades. Once picked, the yellow stain on the cap may not continue to show itself. The picture below shows the sort of stain that occurs when you first pick one of these mushrooms. This was completely gone within 2 minutes.

yellow stain on cap

Yellow stain on edge of cap when first picked

 

The partial veil on these mushrooms has a fluffy appearance that I believe can be called flocculose.   The appearance of the partial veil at various stages is shown in the following set of images.

Partial veil at various stages of growth

The yellow stain on the cut stem can also been seen in these images as can the white core in the centre of the stem, a feature that is also seen in supermarket mushrooms.

Another feature that tends to be a characteristic of mushrooms in this Section is the ‘boxy’ cap shape.   That shape can be seen in the first image above.  This is where the analysis gets interesting.  As I have mentioned elsewhere, the yellow stain can be made permanent on these mushrooms by applying an alkali.  The yellow colour is due to 4,4-dihydroxyazobenzene.    While looking closely at these mushrooms I noticed that they have a very distinct internal structure featuring a very dense section in the cap above the stem.   This is revealed in a sectioned piece developed with Napisan solution which provided the necessary alkalinity and perhaps some oxidizing power that might have had an effect.   An example of a sectioned mushroom developed in this way is shown in the pictures below, compared with a supermarket version.

Yellow stainer (top)  compared with normal supermarket mushroom (bottom), both developed with Napisan solution

In this view it is immediately apparent that there is a significant difference in the internal structure of the two mushrooms.  The hard core in the centre of the cap of the yellow stainer shows up clearly.   I strongly suspect that this structure is responsible for the boxy shape of these mushrooms.   Beyond that however, the flesh of the cap of the yellow stainer remains refractory to the effects of the Napisan while the flesh of the supermarket mushroom saturates and slightly darkens.   The hard core also influences the way the cap separates from the stem.   In the case of the supermarket mushroom the separation is very clean but in the case of the yellow stainer the stem breaks away with a rather ragged edge, as shown in the picture below with two yellow stainers on the right and two supermarket varieties on the left.

Cap separation on supermarket mushrooms (left) versus yellow stainers (right).

I have in mind a few more experiments on these interesting mushrooms but I will finish this post off for now.

A quick postscript.  After about an hour the difference between the two mushrooms became even more stark.

 

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Amanita rubescens – The Blusher – an introduced species

The early colonists of Australia were mainly of British origin and they brought with them the trees with which they were familiar.  Such trees include pines and oaks.  With these trees came the fungi that were associated with the roots of the trees.  There are quite of few of these fungi that have now become established in various areas in Australia.  One of these is the infamous Death Cap, Amanita phalloides.

Because of the lethal consequences of eating Amanita phalloides, people have a natural caution about eating anything in the Amanita genus.   This includes some of the most enthusiastic mycophagists, including myself.

I had not been aware of any edible Amanitas in Australia until I heard of Amanita rubescens.  It occurs in the Adelaide hills and in Queensland and probably in places in between.  My encounter with it was in the Adelaide hills.  It was growing in a park filled with oaks and pines and in this case I believe it was growing on the oaks.  Here is what it looks like in its various stages of growth.

rubes

Amanita rubescens at various stages of growth.

Some important general features are the lack of a volva at the base and the presence of ‘warts’ on the surface of the mushroom.  When it is broken open or cut, the white flesh and gills take on a red/pink colour as shown in the next picture.

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Amanita rubescens showing red bruising

There are not too many mushrooms that this could be confused with.  The main one that crops up in the literature is Amanita pantherina.  A distinguishing feature of A. rubescens that sets is apart from A. pantherina is the presence of striations on the annulus.  These are shown in the picture below. You can also see the pink colour of the broken flesh of the cap there.

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Striations on annulus of Amanita rubescens

This mushroom is known to contain a toxic, haemolytic protein that is destroyed by cooking.   This in mind, I cooked some up on a barbecue until they were quite soft.  In fact they were so soft that they did not really appeal much.  This being my first taste of a new mushroom, I tasted the cooked material without swallowing it.  The taste reminded my a bit of Volvopluteus.   I have read reports that it is better cooked hard until it starts to brown.  This is the case with many other mushrooms.

It is scary eating an Amanita for the first time.  People who I know and respect regarding edible mushrooms in Australia cannot bring themselves to eat this one.  My caution was brought into sharp focus the next morning when I felt decidedly ill.  I don’t actually think that this was the mushrooms, as I had felt a little ill the night before with food from the place where I was staying.

I will try this again, next time with hard cooking.

I would like to thank my friend Kate for giving me the heads up about these.  You can see her interesting site about foraging  here. She is in South Australia and really knows her mushrooms.

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Lactarius deliciosus – Saffron milk cap – an east coast favourite.

The Saffron milk cap is a mushroom that occurs widely on the east coast in pine forests.  Foragers are actively encouraged to pick this mushroom in NSW in places like Oberon.  It also occurs in Victoria, South Australia and Tasmania.  Reports from Queensland are rare but it is occasionally found there. Sadly, it is not something we see in the pine forests of WA, though there have apparently been unsubstantiated reports of it from the Kewdale area, according to Bougher and Syme (1998).  There is another mention of someone trying to establish this in WA in an earlier paper. I have certainly never seen it in WA.

To view one of these beauties I had to travel to Adelaide on a heads up from some friends there.  These were cropping up in early February of 2017 after some rain, to the general surprise of enthusiasts there.  There were not a lot of them at this time, but I did manage to find this single specimen, to my great joy.  Thanks to Kate et. al. for the heads up!

This is what it looks like from the top.  Notice the pine needles.

saffie
Lactarius deliciosus cap

When cut, the inner surface reveals an orange colour at the margins, as shown below.

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Lactarius deliciosus showing red cut surface

Some texts say that these mushrooms are not particularly good eating and that the name is in fact a misnomer.  To test this out, I took my specimen down to a the barbecue at a local park in suburban Adelaide and fried it up with a little olive oil.  Adelaide is so well endowed with such parks and barbecues and I am sure that they are a popular gathering place. On this particular day however there was nobody else around though, and perhaps that is because it was 42 degrees. All this reinforces the oddity of finding mushrooms at this time of year.

Anyway, back to the taste test.  I found that the smell and the taste were intimately entwined and that it was a pleasant and unusual taste.  It is hard to describe a smell or taste but I kept thinking of vegetables like carrots.  This may well have been influenced by the orange colour.  The other very distinctive and great thing was the firmness. This is easily the most firm mushroom that I have ever cooked and eaten.

I look forward to eating more of these.  Who knows, perhaps they might crop up in WA?  Time will tell.

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Calvatia fragilis – another edible puffball

While driving around in April, I noticed for the first time this year some rather large puffballs growing around the place.  Here is what they looked like.

puffball
Calvatia fragilis

When cut open, these revealed a firm white flesh with a pleasant mushroom smell.  They lacked a ‘sterile base’ which is the bit at the bottom close to the attachment point to the ground.  The lizard skin pattern was also distinctive.  If left undisturbed they develop a purple spore mass and break open.

Calvatia fragilis spore mass

All of these factors together led me to identify them as Calvatia fragilis, which was subsequently confirmed by DNA analysis (97% AJ684871).

The picture below shows the specimen torn open.  There is a slight yellowing when it is bruised. It has a distinct skin.

Calvatia fragilis torn open
Calvatia fragilis torn open

The next picture shows another view of the surface of the puffball.

Surface of Calvatia fragilis
Surface of Calvatia fragilis

I found something similar in March 2021 after some unseasonal rain and humidity. These were a little more aged than the first ones and the skin (peridium) had become a bit more faceted but I believe it is the same fungus. This specimen turned soft overnight.

Calvatia fragilis immediately prior to spore formation

Some people say that all white puffballs in Australia are edible.   This is not true as many years ago I found a massive white puffball growing next to a mulga tree in Hopetoun that had an extremely unpleasant smell.  When I heated some up it caused us to evacuate the kitchen!

Calvatia fragilis is edible though and I sliced this one and fried it in butter.  The taste reminded me a little of eggs.

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Rhizopogon – a taxonomic challenge

A walk in a pine plantation in WA during winter will often reveal a truffle-like fungus lying on the top of the ground or sometimes almost buried.

rhizopogon-pseudoroseolus

Rhizopogon pseudoroseolus

This is Rhizopogon, introduced with the pine trees and a very effective fungus for assisting the pines to grow.  The mycelium from fungi such as these acts as an extension of the roots of the trees, drawing in nutrients that would otherwise be unavailable to the trees.

Many sources report that the species occurring here are Rhizopogon luteolus but DNA results on the specimen pictured above match R. pseudoroseolus (GQ267483).  This species, an introduction from the USA is also very common in New Zealand, though the appearance does not appear to match either the image nor the key published by Jerry Cooper of the Fungal Network of New Zealand. There are many different species, lots of variability and many published revisions of this genus so it does make identification difficult.

In Japan, a member of this genus, Rhizopogon roseolus is much prized as a food where is it known as Shoro.  The Kiwis, always much more proactive on these matters than we are, have done some comparisons on the species growing in New Zealand with those in Japan and have gone so far as introducing the Japanese species into NZ as a potential agricultural product.

This is not an easy fungus to identify visually and there is sparse information about edibility.  My friend Jsun has eaten a species that grows in Queensland and while visiting here he pickled some that I had collected.  These are shown in the picture below.  He has selected specimens that were firm and had a white interior when cut in half. When pickled, the outside became quite distinctly reddish.

rhizopogon-jar

Pickled Rhizopogon pseudoroseolus

I have eaten small quantities of these and must say that they are rather bland. Jsun reports that he likes to add them to stews and so forth and that they soak up the flavor of the dish.

See also: https://mushroaming.wordpress.com/2015/12/26/rhizopogon-rubescens/

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