Foraged Foods, the Permanently Fresh, Hidden In Plain Sight, Survival Food

Prepper people are fond of storing all sorts of survival foods - from buckets of grains, beans, rice and pantries of canned foods but they all expire leaving the preppers to consume uninspiring, nutritionally diminished foods or worse, leave all that money at the curb to be dumped into a landfill.  
Stored food is certainly part of a good plan but only as an alternative to starving.  Fresh food is essential to maintaining good health.  There is little point in eating foods that put you, and your companions in a compromised health condition requiring medical intervention that may not be available.  
Man survived, and thrived on nature's bounty found at our feet.  It only takes a bit of knowledge to unlock virtually unlimited stocks of healthy wild foods.  
Purslane, Lambs Quarters and Red Root (wild Amaranth) are fetch handsome prices at upscale stands near New York city.  Most "weeds" are the foundations of our domesticated vegetables.  there are few poisonous plants but KNOW THEM before you even attempt to forage for food.   

Red Root - Amaranthus retroflexus

The first step is knowing what, when, where and how to harvest wild foods.  The second, and possibly the most important knowledge, is how to use the food in recipes - if you find the food unpalatable you aren't going to actually eat it.  Recipes unlock the food for you to use it.  Here's just an example of recipes for Purslane.           
Samual Thayer's books ("The Forager's Harvest" and "Nature's Garden") are fantastic references, as are Steve Brill's books, ("Identifying and Harvesting Edible and Medicinal Plants in Wild (and Not So Wild) Places").