There's a wide selection of books in the library about wilderness survival, if you wanted more information. A lot of it is basic knowledge, like how to make a shelter with minimal supplies, but there is still enough information about what plants are safe to eat raw or how to cook them until they're safe.

[Like fiddleheads. It's recommended that they're boiled before eating. The same went for many mushrooms...]

I'd be careful with mushrooms, if I were you. There's too much variability to be certain that they're not poisonous. The same goes for anything related to carrots or celery, as it's too easy to confuse them with hemlock in the wild.