The potato is a starchy, red or brown skinned, underground stem called a tuber. Tubers are storage areas for nutrient reserves of plants, such as starch or sugars. A widely cultivated species, the potato plant has the scientific name Solanum tuberosum and is a member of the nightshade family of plants, Solanaceae. Potato plants are widely grown for their familiar edible tubers that are a mainstay of many human diets.
Potato plants are flowering plants with flower colors that include white, purple, violet, or lilac depending on the variety of plant. Natural potato plants produce a tap root system that is difficult to harvest. Cultivated potatoes, in contrast, have fibrous root systems that are more easily removed from soil, making potato harvesting less difficult. Potato tubers have indentations, called eyes over their outer surfaces. The eyes are places where new stems may grow outward from tubers. Also, stolons grow from tuber eyes. Stolons are underground root-like extensions that connect tubers to one another and link individual potato plants together vegetatively.
Potatoes are a very important food source for humans. The starchy content of potato tubers provides a good source of energy, and the vitamin content of potatoes is exceptional. A single medium sized potato (about 5.5 oz or 148 g) contains about 100 calories with no fat. They are easily digested since starch is quickly converted into simple sugars, which are absorbed rapidly for use by the body. Also, potatoes have a high water content. To illustrate their importance, it is reported that the average American consumes about 140 lb (64 kg) of potatoes each year. According to the USDA, that includes about 50 lb (23 kg) of fresh potatoes, 60 lb (27 kg) of frozen potatoes (including French fries), and 16 lb (7 kg) of potato chips per person per year. In the United States, Idaho grows more potatoes than any other region and accounts for about 30% of all potatoes cultivated in the United States.
A significant historical event concerning potatoes was the Great Irish Famine. In the nineteenth century, potatoes had become the major food source of the population of Ireland because of its ease in cultivation. The climate and moisture of the country was favorable for potato growth. However, in 1845, a devastating plant disease infected the potato crops across Ireland. The disease (which still can occur) is called the late blight, or simply the potato blight. It is caused by a fungus. The parasitic fungus, with the scientific name Phytophthora infestans, resulted in mass ruin of potato crops for several consecutive years, creating horrible famine. In order to escape hunger, many Irish people fled to America and Canada. In this manner, the potato famine contributed to American immigration and the growth of the Irish population in the new world.