Blogger's Note: With the holidays right around the corner, let's investigate one of the South's favorite tubers, the sweet potato and what sets it apart from the traditional yam.
(Above): A true yam (left) compared to an orange-fleshed sweet potato (right).
is the difference between sweet potatoes and yams? Although
yams and sweet potatoes are both angiosperms, flowering plants,
they are not related botanically. Yams are a monocot, a plant having
one embryonic seed leaf, and from the Dioscoreaceae or Yam family.
Sweet Potatoes, often called ‘yams’, are a dicot, a
plant having two embryonic seed leaves, and are from the Convolvulacea
or morning glory family.
(Above): An example of African yams.
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.
(Above): These are Louisiana Sweet Potatoes.
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