Know your Sweet Potato

Freshly dug sweet potatoes
  • Sweet potatoes (Ipomoea batatas) are perennial dicots in the morning glory family (Convolvulaceae) which are cropped as annuals.
  • Sweet potatoes should not be confused with yams which are monocots in the family Dioscoreaceae
  • Its large, starchy, sweet tasting tuberous roots are an important root vegetable. 
  • The young leaves and shoots are sometimes eaten as greens. 

Know your Sweet Potato - Botany

  • This plant is a herbaceous perennial vine, bearing alternate heart-shaped or palmately lobed leaves and medium-sized sympetalous flowers. 
  • The edible tuberous root is long and tapered, with a smooth skin whose colour ranges between red, purple, brown and white. 
  • Its flesh ranges from white through yellow, orange, and purple.
  • The sweet potato is only distantly related to the potato (Solanum tuberosum). 

Know your Sweet Potato - Origins

  • The sweet Potato is native to South America. It has been cultivated there since at least 2500 BC.
  • Sweet potatoes have been cultived in the Pacific since 1200 AD. How they got there is uncertain.
  • Of the approximately 50 genera and more than 1,000 species of Convolvulaceae, Ipomoea batatas is the only crop plant of major importance, some others are used locally, but many are actually poisonous.
  • The genus Ipomoea that contains the sweet potato also includes several garden flowers called morning glories, though that term is not usually extended to Ipomoea batatas. 
  • Some cultivars of Ipomoea batatas are grown as ornamental plants; the name "tuberous morning glory" may be used in a horticultural context.

Know your Sweet Potato - Distribution

Sweet Potato in China

  • 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.

Sweet potato in Asia

  • Sweet potatoes very early became popular in the islands of the Pacific Ocean, spreading from Polynesia to Japan and the Philippines. 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 favourite dishes in Japan, Taiwan, the Philippines, and other island nations. 
  • Indonesia, Vietnam, India, and some other Asian countries are also large sweet potato growers. 

Sweet potato in Africa

  • 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. 

Sweet potato in the Americas

  • North and South America, the original home of the sweet potato, together grow less than three percent of the world's supply.

Sweet potatoes in Europe

  • Europe has only a very small sweet potato production, mostly in Portugal. 

Sweet potatoes in the Caribean

  • In the Caribbean, a variety of the sweet potato called the boniato is very popular. 
  • The flesh of the boniato is cream-coloured, unlike the more popular orange hue seen in other varieties. 
  • Boniatos are not 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 in the USA

  • Sweet potatoes have been an important part of the diet in the United States for most of its history, especially in the South-east. 
  • From the middle of the 20th century, 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 (3.3–4.4 lb) per year, down from 13 kg (29 lb) in 1920. 
  • Southerner Kent Wrench writes: "The Sweet Potato 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."
  • Several decades ago when orange flesh sweet potatoes were introduced in the southern United States producers and shippers desired to distinguish them from the more traditional white flesh types. The African word "nyami" referring to the starchy, edible root of the Dioscorea genus of plants was adopted in its English form, "yam". 
  • Yams in the U.S. are actually sweet potatoes with relatively moist texture and orange flesh. Although the terms are generally used interchangeably, the U.S. Department of Agriculture requires that the label "yam" always be accompanied by "sweet potato." 

Sweet potatoes in New Zealand

  • New Zealanders grow enough kūmara to provide each person with 7 kg (15 lb) per year, and also import substantially more than this from China.

Know your Sweet potato - Uses

  • Cooked as a vegetable and used to make pies.