This is the only grain that's commonly eaten as a fresh vegetable. Native to the Americas, corn is a great source of vitamin A, fiber, and other nutrients.When corn comes into season during the summer, it's common to see people in supermarkets peeling back husks in search of ears with perfect rows of kernels. Don't do that yourself. Crooked rows taste just as good as straight, and keeping the husk on helps the corn stay sweet. Freshness is a better criterion, since the sugars in corn begin converting into starch the moment it's picked. The best test is to sample some kernels. Frozen corn kernels are a good substitute when fresh corn is out of season, but canned corn is only a fair substitute.