"rule of thumb" to tell if something is poisonous

Hi, Peter! I would love to grow mushrooms but am a little nervous about tasting them. Is there any "rule of thumb" about how to tell if something is poisonous. What is you advice for someone who has never grown her own and does not want to poison herself?

Cynthia Carter wrote:Hi, Peter! I would love to grow mushrooms but am a little nervous about tasting them. Is there any "rule of thumb" about how to tell if something is poisonous. What is you advice for someone who has never grown her own and does not want to poison herself?

If in doubt, ask an expert, but it is possible to obtain spawn from reputable suppliers, with instructions for inoculation. It's a pretty safe bet that what then comes up is an edible species (although somebody, somewhere, will react badly to just about anything: this applies especially to mushrooms, many of which have an interesting biochemistry, so always try a little first to make sure you don't react to it), especially if it looks like the picture.

There is an urban myth that if the cap peels it's edible. Yeah, the death cap (Amanita phalloides) peels, and it's aptly named. Actually, to be on the safe side, avoid any parasol-shaped mushroom with white gills unless you bought it somewhere reputable.

Also, don't eat Little Brown Mushrooms: there are too many similar ones.

One of my favourites, the ink cap (Coprinopsis atramentaria) is edible, but drinking alcohol will change that.

A couple of people not too far from where I live mistook web caps (Cortinarius rubellus, formerly C. speciosissimus) for an edible species, and ended up in intensive care for severe renal failure. Fortunately they didn't share their find with the kids.

There are plenty of poisonous mushrooms that look like edible ones.

Other rules of thumb that can get you killed include:
* If another animal eats it, it's fine (nope)
* Peeling it removes the poison (ahah)
* All brightly coloured mushrooms are poisonous (sometimes: I like wine caps (Stropharia rugosoannulata), and this is a good beginner's mushroom, but the sickener (Russula emetica) fits the bill)
* If it smells good, it's edible (not necessarily: Jack-O'-Lantern (Omphalotus olearius) is to be avoided).

Your best bet is to learn from an expert, in the field, and not guess.

Ever.

To Neil Layton:

This is the first time I have ever tried to reply to someone on a forum. I hope I am doing this right because I really would like to let you know how much I appreciate your long reply! The bottom line is that I need an expert to help me at first as I do not have a clue about which are edible and which are poisonous. Rest assured, I will not nibble until I ABSOLUTELY know what I am doing. Thanks again!!

The only real way to do it is to find a list of toxic mushrooms present in your area and get good at identifying as many of them as possible.

It's time consuming, but if you REALLY want to get into mushroom hunting, it's a great place to start! Besides, it's more important to learn what NOT to eat at first.

Miriam is absolutely right.
AND, if you want a rule, this one helped me when starting out with book knowledge but no experts my area.

Some young gilled mushrooms begin life in a sack that conceals their gills. (example, destroying angel and death cap)
Not all mushrooms with gills are deadly poisonous. (example, grocery store mushrooms)
ALL deadly poisonous mushrooms have gills. (example, destroying angel and death cap)
THEREFORE, if you don’t know for sure,

Never taste a gilled or a premature mushroom.

Miriam Johnson wrote:The only real way to do it is to find a list of toxic mushrooms present in your area and get good at identifying as many of them as possible.

It's time consuming, but if you REALLY want to get into mushroom hunting, it's a great place to start! Besides, it's more important to learn what NOT to eat at first.

I am not arguing with this but it is the exact opposite of my approach.  I have learned a few of the most common edible mushrooms in my area -- well enough to be confident in my identifications.  

I don't give any other mushrooms a second glance.  Just not interested.  If they're not common and numerous and easy to find in good quantity (like oysters, which sometimes present thirty or forty pounds on a single old tree trunk around here) it's easier just to assume everything I see that I don't recognize is poisonous.  

Since the OP asked about growing mushrooms, her problem is a lot easier than the mushroom hunter's problem.  She's going to have just one or two or a few kinds of mushrooms that are supposed to be growing where she put them.  The first time she grows a crop, she could (if necessary) go to the nearest fancy food store and buy a plastic clamshell of the kind she is growing, and compare them side by side.  Once she's grown a successful crop, she'll be so familiar with that kind that she'll never have trouble telling if subsequent crops are the same thing.  The odds of a dangerous look-alike growing in her sterilized spawn are not high enough that I would choose to worry about that.

Amy Gardener wrote:Miriam is absolutely right.
AND, if you want a rule, this one helped me when starting out with book knowledge but no experts my area.

Some young gilled mushrooms begin life in a sack that conceals their gills. (example, destroying angel and death cap)
Not all mushrooms with gills are deadly poisonous. (example, grocery store mushrooms)
ALL deadly poisonous mushrooms have gills. (example, destroying angel and death cap)
THEREFORE, if you don’t know for sure,

Never taste a gilled or a premature mushroom.

Realistically, it's more like never eat a gilled mushroom. Counterintuitively it's safe to nibble and spit pretty much any fungi, as all known toxic species must actually be eaten to present a problem.

Shame that isn't true for plants though.

Dan Boone wrote:

I am not arguing with this but it is the exact opposite of my approach.  I have learned a few of the most common edible mushrooms in my area -- well enough to be confident in my identifications.  

I don't give any other mushrooms a second glance.  Just not interested.  If they're not common and numerous and easy to find in good quantity (like oysters, which sometimes present thirty or forty pounds on a single old tree trunk around here) it's easier just to assume everything I see that I don't recognize is poisonous.  

Since the OP asked about growing mushrooms, her problem is a lot easier than the mushroom hunter's problem.  She's going to have just one or two or a few kinds of mushrooms that are supposed to be growing where she put them.  The first time she grows a crop, she could (if necessary) go to the nearest fancy food store and buy a plastic clamshell of the kind she is growing, and compare them side by side.  Once she's grown a successful crop, she'll be so familiar with that kind that she'll never have trouble telling if subsequent crops are the same thing.  The odds of a dangerous look-alike growing in her sterilized spawn are not high enough that I would choose to worry about that.

That method also works! The reason why I emphasize learning the significantly toxic ones first is because it also eliminates the beginners anxiety of "but what if there's a lookalike to this choice edible mushroom that could kill me?" If you're already familiar with what WILL kill you, that anxiety isn't really an issue.

But then again if you're primarily interested in like morels, lion's mane, chanterelles, chicken of the woods, maitake, etc...that's not much of a problem cause it's well known none of those have deadly lookalikes. And yes, I know there are seriously toxic Gyromitra species that some people say resemble morels, but honestly I don't see the resemblance at all other than "wrinkly fungi".

However, pretty much anything that you'd be deliberately cultivating is pretty distinct looking. I suppose you could find Panus rudis and somehow mistake it for a shiitake (both fibrillose, both grow on decaying hardwoods, but P. rudis is teeny tiny and would taste like chewing on a stick...).

There is no rule that works with mushrooms.  Also, do not eat any wild mushrooms without thoroughly cooking them first, as some species are poisonous or will at least make you sick if eaten raw.  Morels are one example of this.

If you’re growing your own mushrooms, just make sure what comes up is what you thought you were growing.  The only one I’ve had trouble with so far is lions mane.  It grows upward and branches, instead of downward and toothed if it doesn’t get enough fresh air. I’ve had that happen and have talked to other folks it happened to.  They’re still edible.

I’m just entering my third year of hunting wild mushrooms.   I can’t stress enough trying to find a mushroom club in your area to join.

If you’re starting out, stick to the easy ones.  The list above is a good example, so I’ll try to repeat and slightly expand it.  Start with oysters, chicken of the woods (both types, yellow or white underneath), hen of the woods, puffballs (always cut them open, you want pure white flesh and no signs of a mushroom forming inside the puffball), and hedgehogs (Hydnum repandum and umbilicatum), and maybe chanterelles.

Your knowledge of mushrooms seems to multiply exponentially, in my opinion. Last year, we had an extremely dry year.  The only mushrooms I picked in any quantity were meadow mushrooms.   This year was extremely wet and we’ve had mushrooms all over, on a consistent basis.   I have learned so many new species this year, simply because I had a chance to see them for myself, instead of just in a book.

The only “rule” I’ve heard of that our mushroom club observes (I think it was first stated by a very knowledgeable Bolete specialist in another club) concerns only Bolete mushrooms, those that grow on a stem and have pores instead of gills. And this rule may only be based on what we find in the eastern US.

Don’t eat any Bolete that tastes bitter,  bruised blue, or has red pores.

I realize observation of this rule will cause you to bypass some very good edible mushrooms, but it’s probably a good idea for a beginner.  Boletes can be very hard to identify. And there are Boletes that will make you sick, and at least one that is deadly.

Basically, don’t eat anything unless you can identify it.  My rule of thumb on eating a mushroom that is new to me, is that I will not eat it until someone I trust seconds my ID.

Kevin Hoover wrote:The only “rule” I’ve heard of that our mushroom club observes (I think it was first stated by a very knowledgeable Bolete specialist in another club) concerns only Bolete mushrooms, those that grow on a stem and have pores instead of gills. And this rule may only be based on what we find in the eastern US.

Don’t eat any Bolete that tastes bitter,  bruised blue, or has red pores.

I realize observation of this rule will cause you to bypass some very good edible mushrooms, but it’s probably a good idea for a beginner.  Boletes can be very hard to identify. And there are Boletes that will make you sick, and at least one that is deadly.

Basically, don’t eat anything unless you can identify it.  My rule of thumb on eating a mushroom that is new to me, is that I will not eat it until someone I trust seconds my ID.

I would say that the bolete rule is largely true! I can think of a couple edible exceptions, namely I've eaten Hortiboletus campestris on a few occasions and it bruises blue. However, most red-pored boletes will indeed make you feel pretty bad. Bolete deaths are exceptionally rare.  Both Rubroboletus satanas and Boletus huronensis are known to cause VERY VERY SEVERE GI distress though, so perhaps if you were already in rough shape/dehydrated going into eating them they could conceivably kill you, but it would be more from electrolyte imbalances after purging so much.  And there's one Australian report of a woman dying of muscarine poisoning from a Rubinoboletus sp apparently?

All Rubinoboletus and Rubroboletus fit the "don't eat red-pored boletes" rule  though, so Boletus huronensis is the one to look out for, at least in NA. It's found near Lake Huron in hemlock woods (hence the name), and bears a passing resemblance to Boletus edulis if you aren't careful. The stipe reticulation (or rather, the lack thereof) gives it away. It's also very rare.

If you wanna see some mycologists debating its genetics, this is fun https://mushroomobserver.org/observer/show_observation/331948

As for bitter mushrooms: Tylopilus sp almost invariably taste terrible but as far as I know aren't actually toxic beyond a tummyache. I've seen reports of people using them for cocktail bitters, oddly enough!

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On a related note, you can determine the ediblity of anything in Russulaceae by taste. Tastes okay to "meh": edible. Tastes spicy or acrid: you will hurl.

Boletes huronensis is the one I had in mind when I mentioned toxic Boletes.

I also harvest mushrooms from the complex Baorangia bicolor, which bruise blue, but are easy to ID if you know what to look for.

If you notice that I might sometimes use older names for Boletes, it’s because I use Bessette’s “Boletes of Eastern North America” as my baseline.