Georgia designated the sweet Vidalia onion as the official state vegetable in 1990. Internationally acclaimed as the “world’s sweetest onion,” Vidalia onions can be grown properly in only a small pocket of southern Georgia.

Vidalia onions are unsurpassed for sweetness when they mature in the spring.The fields surrounding Vidalia and Glennville in Georgia produce onions from granex seed that are so sweet one can "eat them like apples" (this seed produces a hot onion grown elsewhere, and cannot be called a Vidalia onion - the name is associated with the location).

Source:

State Vegetable: Georgia Secretary of State
State Symbols: Georgia Legislature

Links:

All Food & Agricultural Symbols - Food Holidays