The Strawberry plant.
Ok ok, I realize that seems odd and obvious. You see a strawberry in the woods and you pluck it and eat it. But do you know what to look for in the late fall early winter or even the early spring? Do you only look for the berry?
You also need to look for the leaves.
In this day and age where we don't have to worry about scurvy, we tend to forget that we can get our vitamin C else where. And in the cold of Kansas, oranges do not grow on trees.
Vitamin C is important to your survival. Find that strawberry plant. Dry out the leaves and seep them in hot water. It will make a sweet tea with that much needed Vitamin C.
Did I mention the Vitamin C?