Sweet potato

Sweet Potatoes at a shop in India.

Cultivation
An ornamental sweet potato of the "Ace of Spades" cultivarThe plant does not enjoy frost. It grows best at an average temperature of 24 °C (75 °F). Depending on the cultivar and conditions, tuberous roots mature in two to nine months. With care, early-maturing cultivars can be grown as an annual summer crop in temperate areas, such as the northern USA. Sweet potatoes rarely flower when the daylight is longer than 11 hours, as is normal outside of the tropics. They are mostly propagated by stem or root cuttings or by adventitious roots called "slips" that grow out from the tuberous roots during storage. True seeds are used for breeding only.

Under optimal conditions of 85 to 90 % relative humidity at 13 to 16 °C (55 to 61 °F), sweet potatoes can keep for six months. Colder temperatures injure the roots.

They grow well in many farming conditions and have few natural enemies; pesticides are rarely needed. They can be grown in poor soils with little fertilizer. Because they are sown by vine cuttings rather than seeds, sweet potatoes are relatively easy to plant. Because the rapidly growing vines shade out weeds, little weeding is needed, and farmers can devote time to other crops. In the tropics the crop can be maintained in the ground and harvested as needed for market or home consumption. In temperate regions sweet potatoes are most often grown on larger farms and are harvested before frosts set in.

China is the largest grower of sweet potatoes; providing about 80% of the world's supply, 130 million tons were produced in one year (in 1990; about half that of common potatoes). Historically, most of China's sweet potatoes were grown for human consumption, but now most (60%) are grown to feed pigs. The rest are grown for human food and for other products. Some are grown for export, mainly to Japan. China grows over 100 varieties of sweet potato.

After introduction there, sweet potatoes very early became popular in the islands of the Pacific ocean, from Japan to Polynesia. One reason is that they were a reliable crop in cases of crop failure of other staple foods due to typhoon flooding. They are featured in many favorite dishes in Japan, Taiwan, the Philippines , and other island nations. Indonesia, Vietnam, India, and some other Asian countries are also large sweet potato growers. Uganda (the third largest grower after Indonesia), Rwanda, and some other African countries also grow a large crop which is an important part of their peoples' diets. North and South America, the original home of the sweet potato, together grow less than three percent of the world's supply. Europe has only a very small sweet potato production, mostly in Portugal. In the Caribbean, a variety of the sweet potato called the boniato is very popular. Interestingly, the flesh of the boniato is cream-colored, rather than the more popular orange hue seen in other varieties. Boniatos aren't as sweet and moist as other sweet potatoes, but many people prefer their fluffier consistency and more delicate flavor. Boniatos have been grown throughout the subtropical world for centuries, but became an important commercial crop in Florida in recent years.

Sweet potatoes were an important part of the diet in the United States for most of its history, especially in the Southeast. In recent years however they have become less popular. The average per capita consumption of sweet potatoes in the United States is only about 1.5-2 kg (4 lbs) per year, down from 13 kg (31 lb) in 1920. Southerner Kent Wrench writes: "The SweetPotato became associated with hard times in the minds of our ancestors and when they became affluent enough to change their menu, the potato was served less often."

Nutrition and health benefits
Besides simple starches, sweet potatoes are rich in complex carbohydrates, dietary fiber, beta carotene (a vitamin A equivalent nutrient), vitamin C, and vitamin B6.

In 1992, the Center for Science in the Public Interest compared the nutritional value of sweet potatoes to other vegetables. Considering fiber content, complex carbohydrates, protein, vitamins A and C, iron, and calcium, the sweet potato ranked highest in nutritional value. According to these criteria, sweet potatoes earned 184 points, 100 points over the next on the list, the common potato.(NCSPC)

Sweet potato varieties with dark orange flesh have more beta carotene than those with light colored flesh and their increased cultivation is being encouraged in Africa where Vitamin A deficiency is a serious health problem. Despite the name "sweet", it may be a beneficial food for diabetics, as preliminary studies on animals have revealed that it helps to stabilize blood sugar levels and to lower insulin resistance.[1] Some Americans, including television personality Oprah Winfrey, are advocating increased consumption of sweet potatoes both for their health benefits and because of their importance in traditional Southern cuisine.

Uses
A sweet potato.The roots are most frequently boiled, fried, or baked. They can also be processed to make starch and a partial flour substitute. Industrial uses include the production of starch and industrial alcohol.