The US Marine Corp published a survival guide with a chapter on identifying plants that are safe to eat.
Identification
- Make sure the plant you’re testing is abundant enough to make it worthwhile to test as testing each part of the plant takes a whole day
Avoid:
- Milky sap
- Spines, hairs and thorns
- Mushrooms and fungi (difficult to discern safe from lethal varieties)
- Umbrella shaped flowers (eliminates the deadly hemlock)
- Bulbs (except onions. Only onions smell like onions)
- Grain heads with pink, purplish or black spurs
- Old or wilted leaves
- Plants with shiny leaves
- Almond scent in woody parts and leaves
- White and yellow berries
Edible:
Tip: All aggregate berries are edible (like blackberries and raspberries)
Procedure
Test all parts of the plant for edibility and don’t assume that something edible that’s cooked is also edible raw and vice versa.
Test one part of the plant at a time. Stem, root, flower, bud etc
Smell the plant for strong acidic odors. Note that smell alone is not sufficient to determine if a plant is edible or inedible.
Don’t eat for 8 hours before tasting each part. Only drink water during that time.
While waiting, test for skin reaction by placing the plant part on the inside of your elbow or wrist. The sap or juice should touch the skin. 15 minutes is usually enough to elicit a reaction.
Prepare a small piece of the plant part the way you intend to eat it.
Before eating the prepared plant part, test again by placing a small portion on your outer lip to see if it burns or itches.
If there’s no burning or itching, place a small piece on your tongue and hold there for 15 minutes.
Thoroughly chew a small piece for 15 minutes without swallowing.
If burning or itching occur, rinse your mouth out thoroughly with water.
If nothing abnormal occurs, swallow the food and wait 8 hours. If you have any discomfort or ill effects during this time, induce vomiting and drink a mixture of water and charcoal.
If no ill effects occur, eat 1/4 cup of the plant prepared in the same way, and wait another 8 hours. The plant prepared in this way can be assumed to be safe if there aren’t any ill effects after this time.
As you can see, this is a very involved procedure that requires about 24 hours of testing per plant part.
Important: If you’re thinking about putting this in practice, read Chapter 8 directly here.