Let's play pretend for a moment. Are you with me?

Let's pretend you can't go down to the supermarket for food to eat.

In fact, let's pretend that there is not a supermarket for one hundred miles in any direction, and you don't have any food with you. In this pretend land, you are stranded in the wilderness. Perhaps your GPS navigation unit directed you to detour onto a closed mining road in the middle of nowhere, and you didn't have the sense to second-guess it until your rental car got stuck in seasonal mud, and you decide to head out into the woods instead of following the road back.

Does this seem unlikely? It's happened twice in 2011 so far. Don't discount the possibility.

What this guide is:
This is a guide to wild things that are 100% safe to eat.

What this guide is not:
This is NOT a guide to figuring out if something may or may not be safe to eat. It does not cover plant identification, edge cases, things that are poisonous unless processed in a specific way, etc. If that's what you're looking for, I would suggest starting in chapters 8, 9, and 10 of the US Army Field Manual 21-76.

This is very easy to make 100% foolproof. Unless you are in the Amazon basin, where it is reported that there is a potentially toxic exception to this rule, aggregate berries are all safe to eat. Aggregate berries look like raspberries, blackberries, and Boysenberries - clusters of smaller "droplets" that may or may not have hair, seeds, or tiny leaves mixed in.

Unless you are completely sure, do not eat non-aggregate berries - berries that are shaped like blueberries or gooseberries. In contrast with aggregate berries, which are a sure bet, upwards of 90% of white non-aggregate berries are poisonous; more black/blue berries are edible than red berries, but this will be dependent on what species are found in the area. Depending on the biome and season, you're much better off going hungry than playing berry-roulette, and just because animals eat a berry doesn't mean it's not poisonous to people!

Green Stuff
Most "green stuff" is not outright toxic, but can definitely cause you some distress. It's not a great idea to eat random handfuls of leaves or grass or moss. It probably won't kill you, but it can definitely cause you to wish you were dead. I've avoided listing anything that requires very much knowledge of plants or identification characteristics.

Note: You should use caution when eating any plant, particularly plants found in the water - they can harbor any creepy crawly that may have been living in the water, including giardia cryptosporidium among others. When in doubt, boil the hell out of it.

The lateral roots (rhizomes) of the common cattail are edible raw and high in nutrition, though they are tough and stringy. In fact, all parts of the plant are edible, including the flower spike at the top if you can get to it before it opens up and starts to grow hair. Not having the corndog-looking top does make them a bid harder to separate from the other reeds, so if you aren't sure, don't eat it.

Acorn meal (the yellow-orange stuff inside of acorns) is a great food, assuming there are acorns around. Don't gather fallen acorns, they very often are rotten inside or full of foul-tasting worms and worm poop. If no ripe, hanging acorns are available to pick or shake down, check each fallen acorn, including under the cap, for an entry hole made by the worms. Discard wormy acorns, unless you're hungry enough to eat them anyway. Smash acorns open with a rock (or something) and eat the acorn meal raw, or make a paste and cook it to try to improve the taste. If they are bitter, you can leech them in water for a while.

Most nuts with shells are edible, but don't mess around with any that you don't immediately recognize from the big dish on the coffee table during the holidays. Don't eat wild cashews, the fruit is quite poisonous, as are the nuts unless properly roasted.

Don't touch them unless you really know what you're doing. Seriously. If you don't know what you're doing, you're better off risking starvation than messing around with mushrooms.

Never eat wild critters raw! Always skin and dress them! And the best way to cook them is to boil the hell out of them, both to kill parasites and bacteria, and also to save all the nutrients you can rather than letting them drip out.

If it has fur, you can eat it, providing you:

  • Avoid livers, spinal cords, and brains unless you're sure you know what you're supposed to be looking to avoid.
  • Avoid intestines and stomachs in non-herbivores. The stomach contents of strict herbivores can be eaten, if you're hungry enough to try. Lungs are delicious boiled, as are eyeballs. Discard small organs if you don't know what they are. Bone marrow is a good source of nutrition, but again, don't mess around with the spine.
If it has feathers:
  • Follow the same rules as with furred creatures, but do not eat organs, stomach contents, or gizzards of wild birds. These parts are potentially chock full of parasites, and birds eat plenty of stuff (like non-aggregate berries) that are not good for you to eat.
  • Do not eat the skin or outer layer of fat, particularly with seabirds. The skin and outer layer of fat concentrate toxins and parasites in wild birds. These are not like KFC chickens, skin and dress them just like any other critter.
If it has scales and doesn't live in the water:
  • Eat the meat, don't mess around with the rest.
  • Particularly for smaller scaled critters, if the skin seems greasy, oily, or foul-smelling, don't mess around with it at all. This is probably mucous that falls between irritating and toxic, and will get all over everything no matter how you try to cook it.
  • If it's a snake, you are in luck. Snakes are basically a tube of pure lean meat that is full of goop, though sometimes they have a poison injector on the end. Make sure you cut well back from the head, as in some species the poison glands can extend beyond what looks like the limit of the head and into what looks like the "neck".
If it has scales and lives in the water (and it's not a snake):
  • There are no poisonous freshwater fish, and very few poisonous saltwater fish. Don't mess around with pufferfish or any brightly colored saltwater fish. Don't mess around with turtles, unless you can identify and therefore not eat box turtles. They eat the mushrooms that you aren't supposed to eat, and can become toxic themselves.
  • Fish under two inches can be cooked and eaten whole.
  • Fish over two inches should be gutted and cleaned out.
  • Never eat fish raw in a survival situation. Don't eat fish guts, don't eat fish gills, don't eat fish eyes or brains. What's left is fair game - they're basically two slabs of meat held together by a convenient skeleton.
If it doesn't have fur, feathers, or scales:
  • Don't mess with it. Seriously. Leave it alone. There's a good chance it's pretty dangerous in some way, and we're assuming for the purposes of guaranteed safety that you are clueless. Sorry.
  • Some of the few exceptions to this rule are crayfish, lobsters, clams, and other things that are immediately recognizable as food. Don't eat them raw, even oysters - always boil the hell out of them. Don't eat mussels or other saltwater mud-dwellers in the summer months in the tropics, or during red tides.
  • Frogs are another exception to this rule. They are basically the opposite of a snake. They are a big bag of goop with a couple of edible legs attached. Stay away from non-green frogs, particularly in the tropics.
That about wraps it up. Yes, I realize that there are about a hojillion readily identifiable fruits, plants, herbs, and properly labeled cans of food to be found all over the world. This is for people who don't even want to bother with learning to discern leaf shapes, let alone flower colors, stalk layers, fruit differentiation, odor, etc. and so forth. I have also left out the identification of common fruits, though it would have probably padded the writeup a bit, particularly the tropical fruits for my less-adventurous temperate readers. And also, yes, I realize that discarding all of those organs and other bits from critters is a waste of potential nutrients, but if I'm not talking about leaf shapes, why would I talk about liver flukes or discolored spinal cord? In conclusion, I leave you with these two very general and always applicable tips:
  • If you don't know what it is and it's not on the list, don't mess with it.
  • Even if you know what it is, if it IS an animal, or has been messed with by an animal, boil the hell out of it.

References include USA FM 21-76, various US Mil survival schools, and plenty of time in the back country.

I was saved from the error of classifying frogs with the scaly things by the intrepid DonJaime, though, as even he admits, this ruins the fairly elegant rule set. Alas.

doyle insists you needn't boil mulberries. And really, you needn't boil berries or fruits in general, unless you suspect that a critter got to them first.