Edible plants is my hated topic. I hate this topic not because it is hard to write about but because it is the most dangerous part of survival training. There are probably hundreds of books on edible plants however the unfortunate part of it is that sometimes plants can look exactly a like, with one being poisonous and the other not. For this reason I DO NOT endorse trying to learn edible plants unless you take a guide course and learn from an expert. Again learn from a professional not a book.
However for educational purposes I will teach how to semi-tell if a plant is ok to eat or not. First visually inspect the plant. If the plant has oak or ivy shaped leaves with white patches stay away from it. An example of this is of course Poison Ivy and Poison OAK.
If the plant looks ok, then the next thing you can do is break the stem of the plant in question and inspect the sap. If it has milky sap then chances are it is poisonous so you should stay away from it.
The final thing you can do is taste a small and I mean very small piece of the plant on your bottom slip. If it does not have a bitter taste or if after about 3 hours you are not feeling ill then the plant is ok. However I must again state how dangerous this method can be. If you are not trained by a professional then you should not deal with unfamiliar plants.
My final warning about plants is this: If you choose to go and eat plants that you are not sure about then you are needlessly putting yourself in harm’s way. Knowledge will save your life. Remember if there are plants there is something to eat, be patient and find something safe. Do not eat wild plants unless you are trained.