First thing first. Potatoes are not roots. They are only classified as a root vegetable because they grow underground. They are actually a sort of specialized subterranean stem known as a ‘stolon’. Because they are so distended, a more accurate distinction might be ‘tuberous stolon’ or ‘stoloniferous tuber’. Their eyes are buds, which roots lack. Their roots extend from eyes and other roots.
Most cultivated potatoes are of the species Solanum tuberosum. Some of the thousands of cultivars that were developed during the thousands of years that potatoes have been in cultivation are distantly related to other species. Hybridization was a means with which to incorporate desirable characteristics of other species. Potatoes are presently one of the main food crops in the World.
Small potatoes or pieces of potatoes, which are known as ‘seed potatoes’, start to grow in home gardens after the last frost. Potatoes are not grown from actual seed because of the potential for genetic variation. After bloom later in summer, their coarse foliage dies to the ground. Potatoes that grew during the previous season are then ready to get dug. Fruit and all green parts are toxic.