This article lists four plants which can be used to make flour for food.
http://www.offthegridnews.com/off-grid-foods/4-common-plants-you-didnt-know-you-could-turn-into-flour/The four are:
1) Amaranth
2) Acorns
3) Rye Grass
4) Cattails
Details are included on processing for flour production, from using a mortar and pestle to a food processor.
Warnings about using sandstone or limestone to grind grains. They will crumble and the resulting sand in your food will damage teeth.
NOTE: We have Acorns and Cattails growing locally and Amaranth can be planted in our climate. I don't know how well Rye Grass will grow in our area...