There are nine standard varieties of tuber crops including cassava, yam, potato, sweet potato and aroids, such as carrots and turnips. Some tuber crops, such as yams and potatoes, are umbrella categories that contain a number of sub-species within their families. Many species of tuber crops occur naturally, but technologies allow for the creation of a variety of hybrid species as well.
The tuber crops vary widely in appearance and have distinct flavors, but share several commonalities that distinguish them from other types of crops. Tuber crops typically have high moisture contents and have cells that contain an abundance of starches, which exist in tiny grains. Some tuber crops, such as yams, are sensitive to changes in the surrounding atmosphere. These crops are most flavorful and have the highest water content when consumed immediately after picking or when stored properly after being plucked from the vines on which they grow. Once stored, tuber crops typically have much longer shelf and storage lives than many types of fruits and vegetables. The hardy nature of these crops makes them ideal for serving as food supplies in many areas of the world as they grow quickly and can be stored to use as reserve food sources during times of scarcity.