Sweet Potato vs Yam

Sweet Potato

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.

Yams, which are rarely seen in the U.S. and Canada but are a staple in tropical regions, can grow up to seven feet in length. The word "yam" is thought to derive from the West African word nyami, which means "to eat."

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Sweet Potato


Growing season 90 to 150 days (120= Jewel) 180 to 360 days
Propagation Transplants/vine cuttings Tuber pieces
Chromosome number 2n=90 (hexaploid) 2n=20
Edible storage organ Storage root Storage root
Number per plant 4 - 10 1 - 5
Scientific Name Ipomoea batatas Dioscorea Species
Plant family Morningglory (Convolvulaceae) Yam (Dioscoreaceae)
Plant group Dicotyledon Monocotyledon
Origin Tropical America (Peru, Ecuador) West Africa, Asia
Appearance Smooth, with thin skin Rough, scaly
Taste Sweet Starchy
Availability (in the US) Grown in USA Imported from Caribbean
Climatic requirements Tropical and temperate Tropical

edit Source of 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 sweet potatoes!

Comments: Sweet Potato vs Yam

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January 11, 2008, 11:06am

Thanks for the explanation. Here in WR there is some confusion between the two. The stores label the smooth red skin as yams, and the rougher,white skinned and narrower as sweet potato!

— 70.✗.✗.79

March 14, 2010, 7:29am

Sweet Potato has more starch.

— 166.✗.✗.140
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