Yams are closely related to lilies and grasses. Native to Africa
and Asia, yams vary in size from that of a small potato to a
record 130 pounds (as of 1999). There are over 600 varieties
of yams and 95% of these crops are grown in Africa. Compared
to sweet potatoes, yams are starchier and drier.
The many varieties of sweet potatoes (Ipomoea batatas) are members
of the morning glory family, Convolvulacea. The skin color can
range from white to yellow, red, purple or brown. The flesh also
ranges in color from white to yellow, orange, or orange-red.
Sweet potato varieties are classified as either ‘firm’ or ‘soft’.
When cooked, those in the ‘firm’ category remain
firm, while ‘soft’ varieties become soft and moist.
It is the ‘soft’ varieties that are often labeled
as yams in the United States.
Why the confusion?
In the United States, firm varieties of sweet potatoes were produced
before soft varieties. When soft varieties were first grown commercially,
there was a need to differentiate between the two. African slaves
had already been calling the ‘soft’ sweet potatoes ‘yams’ because
they resembled the yams in Africa. Thus, ‘soft’ sweet
potatoes were referred to as ‘yams’ to distinguish
them from the ‘firm’ varieties.
Today the U.S. Department of Agriculture requires labels with
the term ‘yam’ to be accompanied by the term ‘sweet
potato.’ Unless you specifically search for yams, which are
usually found in an international market, you are probably eating
a day: Vegetable of the month: Sweet potato -
Centers for Disease Control and Prevention’s 5 a
day Web site highlights a fruit and vegetable each month.
The sweet potato page includes nutritional information,
preparation tips and great tasting recipes.
- How the Farmer can save his sweet potatoes by George Washington Carver (1937) -
This Article provides information on the origin, history and growing of sweet potatoes, as well as recipes.
Institute of Tropical Agriculture -
A brief description of the use of yams.
- Practically Edible: Sweet Potatoes -
Article about sweet potatoes, along with recipes
- Practically Edible: Yams -
Article about yams, along with recipes
- Sweet Potatoes from LSU AgCenter (Louisiana State University Agricultural Center -
LSU AgCenter provides articles on the history, best practices, economics, history and management of Louisiana sweet potatoes.
Plant Database - A helpful database of information about the plants in the U.S. and its territories. It provides information such as characteristics, distributional data, images, and much more.
is the difference between a sweet potato and a yam? -
An article by Jonathan Schultheis of the Department of Horticultural Science at the North Carolina Cooperative Extension Service of North Carolina State University, comparing several characteristics of
sweet potatoes and yams.
D. G. Yams: an account of the nature, origins, cultivation
and utilization of the useful members of the Dioscoreaceae. London, Longmans, c1967. 230 p.
Alan. Sweet potato. In The Oxford companion to food.
New York, Oxford University Press, c1999. p. 774-775.
Alan. Yam. In The Oxford companion to food. New
York, Oxford University Press, c1999. p. 856-857.
J. B. Sweet potatoes: production, processing, marketing. Westport,
CT, AVI Publishing Company, c1971. 334 p.
Kenneth F., and Kriemhild C. Ornelas, eds. Sweet potatoes
and yams. In The Cambridge world history of food. New
York, Cambridge University Press, c2000. p. 207-218.
- Price, Robert Henderson. Sweet potato culture for profit. A full account of the origin, history and botanical characteristics of sweet potato. Dallas, TX, Texas farm and ranch publishing co. 1896. 107 p.
- Sweet potatoes and yams. New York, Medina, Ohio, The Barrett company, Agricultural dept., 1918. 15p.
potatoes getting to the root of the demand. Agricultural
outlook, no. 269, Nov. 2002: p. 13-16.
Don. What’s the difference between a sweet potato
and a yam? In Why does popcorn pop? Seacaucus, NJ., Carol
Pub. Group, c1995. p. 42-43.
more print resources...
Search on "Cooking (Sweet potatoes,)," "Sweet potatoes," or "Yams"
in the Library of Congress Online
sweet potato cultivar Ruddy
Agricultural Research Service,
Department of Agriculture.
Man coming out
of jungle with wild yam "cabezo de negro". Prints
& Photographs Division, Library of Congress.
A watercolor sketch, ca. 1930, by Ibo artist D. L. K. Nnachy, depicts a dance celebrating the harvest of new yams. ( Reproduced by courtesy of the Harmon Foundation)
Sweet potato or yam with plant growing in the background. Prints & Photographs Division,
Library of Congress.
up and loading sweet potatoes. Prints & Photographs Division,
Library of Congress.
Preparing sweet potatoes for dinner.
Prints & Photographs Division,
Library of Congress.