The best advice is not to unless you are very, very sure.
Having said that, and just for fun, assuming you are in a chronic survival situation with no choice, this article describes how to test if a plant is edible.
outdoors.stackexchange.com/users/6/Graham
Eating berries and mushrooms is not recommended since there is no general pattern to identify poisonous ones (unless you're an expert on that topic).
Even having a book with pictures of edible berries can be tricky as some poisonous ones are disguised as their edible counterparts.
Plants, on the other hand, should not be edible if the sap is milky.
Milky sap often means poison.
Take, for instance, Euphorbia which can look like cacti and trick you.
So check the sap.
With insects it's easier.
Not eating the flashy coloured, smelly or slow unwary moving ones is the rule of thumb here.
outdoors.stackexchange.com/users/105/Thomas Rawyler
Get a good book, with full color illustrations.
I can't find a link for one, but you want quality equivalent to the Audubon full color field guides.
Do a few field runs in the area you plan on being in with someone experienced before you try to eat the foliage.
Of course, everything depends on risk.
If you've been lost for four or five days and you're starving, assuming non-bitter, non-burning =
okay may seem more reasonable.
However, if I'm found on the brink of starvation, I generally don't want the response personnel to also have to deal with whatever I may have poisoned myself with.
Seems a lot like doubling down on death.
outdoors.stackexchange.com/users/127/Russell Steen
In general, worldwide this is very hard to predict unless you're an expert in the subject (and therefore likely wouldn't be looking for advice on this page!)
There are some clues, like plants with milky sap tend to be poisonous - but applying these in a general context is almost always a bad idea since your life can depend on it.
The best you can do is to read up, get a good book etc.
that focuses around the area you're hiking to - get one as specific as you can, with good, clear descriptions and pictures.
This will enable you to have at least some degree of confidence -
though obviously unless you're 100% sure I wouldn't risk it.
outdoors.stackexchange.com/users/74/berry120
It is plant specific AFAIK.
But i heard somwhere, that if you taste poisoned berries or fruit it will taste strange - because of evolution - whoever can detect poisonous berry by taste will not eat it and will live longer :-)
outdoors.stackexchange.com/users/115/SergeS
As other answers say, don't just try it.
A good negative indicator is skin irritation.
I've read that particularly with berries, if you crush some berries and rub some of the juice on a patch of skin and let it sit for a while, some berries will cause irritation, which is a good indicator not to eat them!
But berries that don't irritate your skin aren't necessarily safe...
outdoors.stackexchange.com/users/265/Gregor Thomas
Do NOT try this at home.
But if your life depends on it and you can't find anything you know is edible, you can follow these instructions.
Again, you may die by doing this but if the odds are you'll die anyway
, you can play roulette with your life as safely as you can.
Rub the plant on an area of your skin where the skin is thin and soft.
Any itching or unpleasant feeling within an hour or two should lead to leaving the plant out of question.
If the plant won't irritate your skin, follow the next steps only following to the next one if previous step won't lead to unpleasant feelings within 5 minutes of exposure Rub it a little to your lips Rub it a little to the side of your mouth
Rub it a little to the tip of your tongue
Rub it a little underneath your tongue Chew
a small portion of it Swallow a small portion and wait for 5 hours If no unpleasant symptoms arise (pain, tickling, burps, nausea, stomach pain, cramps in abdomen or anythin else), consider the plant relatively safe to eat There are 2 most common poisons in the plant world.
Learn to detect them and ditch any plant you suspect containing them.
Hydrogen cyanide Smells and tastes like sweet and bitter almonds or peach.
Oxalic acid Tastes like rhubarb or wood sorrel.
Avoid Plants that have milk-like sap Plants that have red in them Fruits that are divided to 5 sections Grasses and other plants that have small spikes in them.
With a magnifying glass you'll notice the spikes have a hook in them which can really mess up with your intestines Old and withered plants.
Many plants generate hydrogen cyanide when in stress Full-grown ferns as they destroy vitamin B and can cause death.
However, all ferns are edible as young although some species may taste awful Typha Learn to recognize them.
The genus is largely distributed in the Northern Hemisphere, where it is found in a variety of wetland habitats.
The rhizomes are edible.
Evidence of preserved starch grains on grinding stones suggests they were already eaten in Europe 30,000 years ago.
A small area of typha will produce you large amounts of rhizomes, food equivalent to potato.
You can eat them raw but preferably boiled.
outdoors.stackexchange.com/users/13063/Jani Hyytiäinen
In the bush.
You set very still at about 50 meter.
Watch.
Do the monkeys eat them?
If so safe to eat.
You can also walk up look & see if the monkeys have been into them.
A good sign.
outdoors.stackexchange.com/users/12302/J Bergen
How can I identify edible berries/fruit in the wide and avoid the poisonous varieties? Is there a general guideline that can be followed or is specific to each plant?
How can I identify edible berries/fruit from poisonous?
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<survival><food><plants><foraging><edible>
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outdoors.stackexchange.com/users/5/studiohack
The best advice is not to unless you are very, very sure.  Eating berries and mushrooms is not recommended since there is no general pattern to identify poisonous ones (unless you're an expert on that topic). A good book with colour illustrations is recommended, and a good negative indicator is skin irritation. You can read up about this and get a good indication by testing skin irritation, but it's best not to try this unless you are an expert.
You should not try this unless you are an expert. You can read up and get a good book. Skin irritation is a helpful indicator.