What is an Edible Plant?

What is an Edible Plant?

First, of course, it is NOT edible if it will poison you. There are plants that if you eat even a very little bit, you will need hospitalization to survive. (Read this harrowing story of a British child who ate a leaf of foxglove, Digitalis. And see the commentary from The Poison Garden website). Also to be avoided are plants that cause intense discomfort even if the the toxins pass quickly out of the body and cause no lasting harm. We'd call plants with either of these characteristics poisons and recommend to everyone that they do not eat them.

foxglove, Digitalis. Very poisonous

The second point to consider about "Is this plant edible?" is: Should you eat it?

People vary. They have allergies, gluten intolerances, diabetes...Anyone thinking about trying new foods has to be aware that what a "healthy adult" can eat might make a child or someone with a particular allergy ill. Peanuts and pineapple, widespread foods, are dangerous to some people.

pineapple

The third thing to consider: How much of what part are you going to eat?

Quantity, ripeness and plant part matter. A pinch of dry chili in a recipe, no problem. But if you eat two cups full of the same powder, it is likely to produce stomach discomfort. "The green-apple quickstep" was my father's term for the diahrrea produced by eating several under-ripe apples. The same number of fully ripe apples would be no problem. The particular part of the plant we normally eat reflects further safety considerations. Rhubarb stems are edible, rhubarb leaves have too much oxalic acid to be safe to eat.

rhubarb plant

If I take out poisons, individual sensitivities and then choose the right parts to eat, keeping only plant parts that will in fact convey at least some nutrition, I can call all those plants edible. BUT do you necessarily want to eat them? You may not. Some are unpleasantly fibrous. Some are bitter. Some have flavors that repell you.

The real question on a new plant should probably be "Is this enjoyable to eat?" rather than "Is it edible?"

That's a much smaller group. The berries of a number of "edible" fruits are horribly sour. Some of those taste pretty good when cooked with about 50% sugar (for example, smooth sumac, Rhus glabra), others repel me even sweetened (for example, haws, from the European hawthorn, Crataegus monogyna).

But before you call "inedible" a plant whose leaf you tasted and didn't like, answer one last question: How did you prepare it?

Preparation makes a big difference. We are used to plants from grocery stores that have been in cultivation for decades if not millennia. We eat them in particular ways. Most people eat raw lettuce but not cooked lettuce, cooked squash but not raw squash. Wild plants come without recipes. The recipes are crucial. Many leaves that you wouldn't eat raw are very nice indeed cooked. A dramatic example is stinging nettle, (Urtica dioica) which is memorably nasty to touch but delicious when cooked because heat destroys both the prickles and their toxins. Prickly pear cactus (Opuntia) pads (technically, cladodes) are edible but are very mucilaginous (drip goo when cut open). Okra, famously mucilaginous, is delicious prepared by a skilled cook. Treat the prickly pear pads like okra, not lettuce.

stinging nettle, Urtica dioica. It has a nasty sting
if you brush against it, but cooked like spinach it is delicious.

So: Try it if it is not poisonous to you and you enjoy eating it.

When you put all the above together, you get The Real World. Relative to the 400,000 plants worldwide, a few are dangerously poisonous and a few others are enjoyed by everyone. In between those extremes are thousands of plants, many that are nutrious if you enjoy eating them. Be sure to accurately identify the plant and prepare the part recommended, and then, after considering your own health and tastes...go try things! We certainly limit ourselves to only a small portion of the tasty plants of the world and could add lots of interesting things to our diets.

Common chickweed, Stellaria media, a very tasty little weed.

Chenopodium sp., often called wild spinach
because it is related to spinach and tastes similar.

Comments and corrections welcome.

References: 
Foraging Books with Plants You Might Try (beyond the novelty fruits and vegetables at the grocery store)
Blair, Katrina. 2014.The Wild Wisdom of Weeds. Chelsea Green Publishing, White River Junction, Vermont. 
Kallas, John. 2010. Edible Wild Plants. Gibbs Smith, Layton, Utah.
Thayer, Samuel. 2006. The Forager's Harvest. Forager's Harvest Press, Birchwood, WI. (Outstanding information, the plants mainly northern U.S.)
Thayer, Samuel. 2010. Nature's Garden. Forager's Harvest Press, Birchwood, WI. (A broader collection of plants).
Lots of information:

Greene, Dean. Eat the Weeds http://www.eattheweeds.com