|United States range of Burr Oak. Range extends up into Manitoba and Saskatchewan.|
In no particular order
Burr Oak (Quercus macrocarpa) and its hybrids
Applecrabs like Centennial, Trailman and Chestnut (Lucky, please feel free to comment)
Asian pears and its hybrids
Corn also known as Maize
What does it take to make the list? A wide range of adaptability and the ability to produce reliable crops under adverse conditions.