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 the Ag department notes, Perth.  and 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 avensis – 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 Penhurst, 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 mushroom with white gills.  This eliminates the poisonous Amanita and Chlorophyllum.

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.

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.

If in doubt,  there are two approaches you can take;  1) put the mushroom in a plastic bag for 15 minutes and then sniff the contents or  2) cook a piece of the suspect mushroom.  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.  The only stories I have heard of such poisonings have involved the whole group of consumers.  I suspect that the truth is that some people report eating yellow staining mushrooms without ill effect, but they have in fact consumed one of the arvenses group rather than one that contains phenol.

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 ok.   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. Here is a picture of a mushroom that has been tested with sodium hydroxide.

yellow stain with caustic

Yellow stain enhanced with 10% sodium hydroxide solution

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 notorius hallucinogenic ‘gold top’, on the 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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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.

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

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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.  On standing, they developed a purple 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

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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Laetiporus portentosus -White punk, poor tucker indeed

There have been many reports from the times of early European settlement, all from Tasmania, of the Aboriginal people eating a white’ punk’ growing on trees.  It has been widely assumed that this is Laetiporus portentosus, formerly known as Piptoporus portentosus.

This June I chanced upon a specimen of this lying on the ground in Bridgetown.  It was quite a massive thing, weighing several kilos and it was saturated with water.  That is why I assume was on the ground, having fallen from its position because of its weight.  Here it is sitting on my dining room table.

Laetiporus portentosus desk

Fallen Laetiporus portentosus on table

 

Here is another shot of it, this time showing the inside after I had cut it open with great difficulty.  I don’t think this would have been possible with primitive tools.

Laetiporus portentosus cut

Laetiporus portentosus cut open

You can see that the inside looks sort of cottony.  In fact it more closely resembles polystyrene in texture.  An attempt to eat a small piece of it revealed that it was about as edible as polystyrene too.  Not even in an emergency could anyone possibly eat and digest this fungus.  Perhaps the story is different with very small specimens but I am doubtful.

It is quite difficult to get a picture of one of these in-situ on a tree because they tend to grow quite high up.  I was lucky enough to spot one by a road cutting near Donnybrook that enabled me to scramble up and take a picture with my phone.  Here it is.

laetiporus donnybrook

Laetiporus portentosus in situ

The fact that these are relatively few and far between and so high up on the trees is further evidence against them being used as food.

It is however widely reported that they were used as tinder and to carry fire.  Some experiments revealed that a dried specimen could be ignited very readily and that it would smolder for a long time.  By judicious control of the fire front on a smoldering specimen it could easily be kept aglow for hours.  Uncontrolled burning of half a specimen lasted about 40 minutes.  I made a short video of a small piece smoldering after it had been ignited. A still from that video is shown below.

laetipurus glowing

A piece of Laetiporus portentosus smoldering

 

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Macrolepiota clelandii – not for the moment

This is a common mushroom around the karri forest and other places during the early part of the rainy season.  It used to be listed as Macrolepiota konradii in guides until quite recently until Else Vellinga renamed the group in 2002.  Almost all sources list this as edible, except for Tony Young who says that this Australian species is of unknown toxicity.

IMG_0725

Macrolepiota clelandii

Its edibility seems to be  based on the fact that is was thought to be the same as the edible M. konradii from Europe.  Since this is now thrown into doubt, if not thrown out completely, I think it a wise precaution to avoid it.  Besides which, I have a general aversion to Chlorophyllum and Macrolepiota due to the fact that they sometimes cause inexplicable gastric distress.  I am sure that some people do eat or have eaten these though, so I list it here for completeness.

Here is a picture of the top surface.

IMG_0717[1]

Macrolepiota clelandii top surface

It is a rather pretty and delicate mushroom that will sometimes spring up in the oddest places.   I had one come up once half way down a post hole that I had left open. The specimen pictured is about 150mm high with a cap 100mm across.  That is a typical size.  They don’t occur as a small mushroom.  In fact, there are some small Lepiootas that look rather similar and some Lepiotas are deadly.

So I will abstain for the moment.

Update: August 2016

My fellow blogger Jsun and I picked some of these during July and he was able to confirm that they were the same as those he had eaten in the east.  I watched him cook and eat some and being thus encouraged I had a small portion myself.  I am now much more confident about these.   One thing he pointed out to me was the ‘snakeskin’ pattern on the stem which also flares out at the base.

 

snakeskin

Snakeskin pattern on stem

The ring or annulus is quite distinctive also,  breaking up in radial splits and being attached at first, but moveable with some encouragement.

macrolepiota ring

Detail of ring

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Leucoagaricus leucothites -with caution

Leucoagaricus

Leucoagaricus leucothites

 

 

Leucoagaricus leucothites was formerly called Leucoagaricus naucinus and with the state of flux in taxonomy at present, it might have another name next year.  It is a mushroom of worldwide distribution, widely known as an edible species but often recommended as a species to be avoided because it shares so many features with a couple of deadly Amanitas. For this reason nobody should attempt to eat these unless they are completely confident in being able to distinguish an Amanita.

I spotted the specimens above by the side of the road, which is a common place to find them.  The caps are bright white with a satin texture.  The shape of the large specimen in the picture is characteristic of this species.   The underside features a hollow stem that widens a little at the base, but does not have a sac or volva like Amanita or Volvopluteus.  The gills are at first white but darken a little at maturity. The spore print is bright white.

It is always a little scary eating something new but even more so when it is something with white gills and a white spore print.   Nevertheless, after much checking and re-checking I fried some up and did a taste test.  From descriptions elsewhere I had expected something more; it tasted just like Volvopluteus gloiocephalus.  The mature specimen even looks a little like Volvopluteus.

One can only wonder how species like this manage to spread so far and wide.   Apparently the spores of this one germinate very readily in a wide range of media so perhaps that has something to do with it.  Anyway, another of our introduced species that is edible for what it is worth.

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