How do I tell which plants are poisonous?

Cecil's Columns/Staff Reports
1

Dear Cecil,

I think you missed a key factor in responding to Jermain’s question of what unknown plants one can safely eat (or at least sample) in an emergency. Your tip no. 6 – Watch what animals eat. – deserves much more respect than you gave it. This is especially true of fruits. I have occasionally come upon a fruitfall in the forest, seen that many fruits had been nibbled by animals, and then partaken, never with seriously untoward results. You were right to note that the digestion of other species isn’t the same as our own, but for the most part you can eat the fruits that another vertebrate animal eats, especially a mammal.

Look at it from the plant’s point of view. There is a biological reason why many plants produce luscious-looking fruits. It serves to attract animals, who consume the fruits, usually in such an untidy way that many of the seeds are dispersed away from the under the parent plant. It is in the plant’s interest for animals to eat the fruits and to do so without ill effect.

Consuming any other part of a plant is a much trickier business. It is seldom in a plant’s interest for animals to eat its leaves, twigs, tubers, etc, and plants very often have compounds to punish those that do. I’m not saying that one can eat any ripe fruit with impunity, but fruits probably provide the surest food source if one is in dire need in a strange place.

Yours in Word Indeed,
Chris Starr

2

I’m not sure I agree with this:

If something is scarce, it might be precisely because it is a popular edible plant among indigenous species. Conversely, abundant plants may be abundant because they are poisonous and are avoided by indigenous species.

3

And here is the link to the relevant column.

4

Fear Itself said:

If something is scarce because it is frequently eaten, that speaks well of its potential as food. The problem is a practical one.

If you have to spend 10 hours a day searching to come up with 1 berry that might potentially be edible, that is not a good use of resources for you to attempt to discover if the berry is edible or toxic. Knowing it is edible and safe does nothing to keep you alive if you have to then spend another 10 hours to find another berry of the same kind.

That’s really what Cecil’s admonition is about. If you don’t know what’s edible, don’t waste time on something that could never provide enough sustenance to save your pitiful ass*. Pick something that there’s lots of, so at least if it doesn’t kill you maybe it will give you enough to eat not to starve.

*No specific ass is intended. Whomever’s ass is out in the wilderness and starving is the pitiful ass in question.

5

My point was, there is probably a reason said plant is plentiful. If the indiginous species won’t eat it, that is a powerful reason to avoid it as well.

6

Someone once told me that all plants are toxic, but we’ve evolved to overcome some of these toxins. Plants, just like animals, don’t want to get eaten. Unlike animals, they can’t run away from their predators. Therefore, they use toxins and other means to keep them from being a staple on someone else’s diet.

Some plants can be eatable in small doses, but toxic in larger doses. One of the ways many mammalian herbivores have overcome that is to eat a wide variety of plants, but only a little bit of a particular plant at a time. This might be a good strategy to follow if you’re stuck eating vegetation you’re not familiar with.

Another strategy is to eat dirt. Elephants, tapirs, bats, and even chimps have been known to eat dirt in order to help deactivate plant toxins, garner other nutrients missing from their diet, or to fight off illness. Unfortunately, eating any old dirt doesn’t do it. These animals are usually looking for something specific such as salt deposits or clays. You might be on the lookout for clay deposits to try incase one of your “tests” don’t go according to plan.

Probably the best strategy is to thoroughly cook whatever you eat. That helps break down plant toxins, and releases many nutrients. It looks like our human ancestors have been cooking for at least the last million or so years, and that we’ve evolved to eat cooked foods. That may be our secret why our species has been so successful.

7

If you can’t find your way back to civilization, your first priority should be shelter and protection from weather. Once you’ve made sure you won’t freeze to death, as Cecil pointed out, your next priority should be water. You’ll do fine without food for several days as long as you have safe drinking water.

As for tip #5, boiling it, I also suggest boiling in several changes of water. You can remove the toxins from young milkweed pods and take the bitterness out of many wild greens this way. Have the water boiling first before you put the plant in it.

If you’re lost in the mountains, your best bet is to walk downhill until you find a stream and follow it until a road crosses it. Once you’re on a paved road you will find a town soon enough.

8

It’s fair to say that all plants have evolved some response to the threat of being eaten, but it’s not always toxins. Sometimes the defense is sharp thorns or prickers, and if you can get past those, the rest is fine. Sometimes the defense is just to regrow and reproduce faster than anything can eat them. And sometimes, as the OP points out, the plant will have parts which have evolved specifically to be good to eat, in return for something that benefits the plant (most often spreading seeds, but there are other arrangements as well).

9

Except that there are lots of toxic fruits - at least, toxic to humans - for example laurel cherries, holly berries, loads of species in the potato family - all produce lovely-looking fruits that are not safely edible to humans.

In a desperate survival situation, you obviously have to do something, but your rule of thumb sounds reckless to me in any other context - you mention that you’ve experimentally eaten fallen fruit you found in an everyday scenario - did this happen in your own locality? - where in the world do you live that you encounter fruiting plant species that you couldn’t have known the identity of in advance?

10

I agree with your point but not for the same reason.
I realize this discussion is about non-poisonous plants, but in an emergency my first instinct would be “Aha! Bait!”

11

I think I remember the Army Field Manual including this advice: If a monkey eats it, you can too. And also this step, tho I don’t remember where the step falls: Put a small piece of the putative edible under your tongue and leave it there a while. Then chew it a while then swallow the chewed portion, but only a tiny bit.

12

I believe those steps were mentioned in Uncle Cecil’s article.
Powers &8^]

13

Plant can be very particular who gets to eat what part. Peppers use capsaicin to discourage mammals from eating the peppers, but allow birds (who don’t feel the effects of capsaicin) to eat them with impunity. I don’t know about other toxic berries, but I assume that they too are animal specific (certain animals can eat them without effect, but others cannot).

You’d think the plant would be happy if we chow down on the berries, but many berries are quite toxic – at least to us.

14

Maybe the difference is that birds eat the berry flesh and drop the seeds, whereas humans swallow the seeds?

But that seems backwards, because humans try to avoid bitter seeds and birds are known to eat seeds - birdseed.

15

Not quite. In both cases, the seeds get deposited with a dose of fertilizer. The difference is that birds, by and large, travel much greater distances than mammals, so they spread the seeds further than mammals do. A seed that gets dropped right next to the parent plant is competition, which you don’t want, even from your own offspring, but a seed dropped a hundred miles away is extending the hot pepper hegemony.

16

It may have to do with the size and scope of the digestive system. Birds are usually small and digest things rather quickly. Plus, they tend to swallow the seed whole. It gets ground in the gizzard, but not as thoroughly as a pair of molars could. A seed can quickly make the journey through the digestive system and come out unharmed on the other side.

Mammals chew their food and something like a deer will produce cud that will go through several trips through the molars. Plus, mammals digest their food longer. A seed might not survive the trip in such good shape.

Fruits that mammals chew tend to be larger in size with very bitter seeds. That prevents the mammal from attempting to chew up the seeds, and the mammal will either leave them alone, or swallow the seeds whole without chewing. Seeds might even be surrounded by a tough pit.

Wonder if this could offer a clue: Bigger fruits are normally okay, but not berries which could be poisonous. Color might be another clue: Avoid bright red stuff. Mammals can’t see red, but birds can, and birds cannot eat larger fruits. Anyone can think of a large fruit that isn’t safe to eat?

My solution: Cook one thing, and then serve it to the person who’s stranded with your. Make a big deal on how you want to fix a nice meal, and that you’re doing it just for them. If that person doesn’t die with in the next eight hours, it’s safe for you to eat. If they do die, you should avoid eating it yourself.

Of course, it’s an awful shame (your friend dying). Seems like an awful waste. He had a nice plump frame, what-his-name had… has…

17

Cashew apples, for one. They’re full of urishiol (the same active ingredient as in poison ivy), and it takes some delicate work to harvest the cashews safely (this is part of why they’re so expensive).

18

Toxicity can be about dosage.

True story:

I am an avid gardener. I share my truck with my neighbor, who is also a gardener and has remote gardens all over town. He uses my truck to haul mulch and compost and rocks and such. As a thanks for this, he often leaves me veggies or plants for my own garden.

One day, I was out in my yard puttering about when I noticed a dozen or so onions carefully placed on the bottom step to my porch. “Oh, nice!” I thought. “Neighbor left me some pearl onions. Yummy!” I took them inside, washed off a couple and chopped 'em up, then tossed them into my stir fry.

About a half hour after eating my stir fry, I was on the phone with a friend and had to hang up on him to run to the bathroom. Everything I have ever eaten – everything anyone has ever eaten – since 1843 came back up. I retched and dry-heaved for about three hours. Finally, my stomach settled, I had a lovely second supper of cereal, and went to bed.

The next day, I stopped by my house after a dentist appointment to let my dogs out. Another neighbor – completely different guy, NOT a gardener – saw me on the porch and waved. “Hey, there, Miss Dogzilla,” he called. (That’s how people talk to each other in the South.) “Did you get those daffodils I left you?”

“Fuck me.” I thought. “Did he just say daffodils? Crap. That explains a lot.” :: face palm ::

So I said, yes, and thank you and he offered to dig up a few more bulbs if I wanted them. I am not interested in daffodils at all, for reasons unrelated to this thread. Anyway, I laughed about it all the way to work, thinking about how embarrassed I was because I didn’t know the difference between pearl onions and daffodils and I’m supposed to be this experienced, knowledgeable gardener… and what idiot eats something without first verifying who it came from and what the hell it is? (This idiot, that’s who!)

Then I started to wonder if I’d poisoned myself or if eating daffodils would eventually give me kidney damage or something, so I Googled it. Turns out that daffodils are highly toxic in large doses and are a very strong emetic in lower doses. (I did not need Google to know that.) Had I been a big fan of French Onion soup and had decided to make French Daffodil soup instead, I would be way too dead to be posting here.

One daffodil bulb = makes you puke. Twelve daffodil bulbs = makes you dead. It’s all about dosage. So the Army Field Guide tip about taste a tiny bit, wait, then eat more? Would have killed me in the Case of the Mysteriously Appearing Daffodils.

BTW, daffodils and onions are both in the allium family, so yes, in fact, they did taste sort of onion-y and slightly earthy. I thought maybe they were just onion sets and my neighbor’s intent was for me to plant them instead of eat them.

19

I think that the idea behind the Army Field Guide recommendations is that if, at any point, the stuff makes you throw up (or makes your skin itch, or numbs your tongue, or whatever) that you skip the rest of the steps and just throw it out.

20

I don’t remember where I heard this, but I was told that monkeys could eat things that would were poisonous to humans. If you’re stuck on a deserted island, look for wild pigs, because if a pig can safely eat it, a human can. Of course if you can locate wild pigs, you’ve already found a source of food. Delicious, dangerous food.