The Nutrition Source Vegetables and Fruits: Get Plenty Every Day

What does "plenty" mean? More than most Americans consume. If you don't count potatoes—which should be considered a starch rather than a vegetable—the average American gets a total of just three servings of fruits and vegetables a day. The latest dietary guidelines call for five to thirteen servings of fruits and vegetables a day (2½ to 6½ cups per day), depending on one's caloric intake. (1) For a person who needs 2,000 calories a day to maintain weight and health, this translates into nine servings, or 4½ cups per day (2 cups of fruit and 2½ cups of vegetables).
http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/vegetables-full-story/