This article is a list of 20 plants that may be found in the wild.
There are excellent pictures for identification.
http://www.theprepperjournal.com/2015/06/13/20-edible-plants-that-could-save-your-life/You could also do some "wild-flower planting" in your county to make sure these plants
are available, just don't tell anyone you do it...
I have grown amaranth and can attest that it offers both edible seed and leaves. It also
re-seeds itself. Unfortunately, it is also bright red and easily seen from a distance.
Amaranth also makes a good cover crop which can be "plowed" back into your soil after
harvest.