NC State Extension Publications


Several decades ago, when orange-fleshed sweet potatoes were introduced in the southern United States, producers and shippers desired to distinguish them from the more traditional, white-fleshed 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 United States are actually sweetpotatoes 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 "sweetpotato." The following information outlines several differences between sweetpotatoes and yams.


Factor Sweetpotato Yam
Scientific name Ipomoea batatas Dioscorea Species
Plant family Morningglory (Convolvulaceae) Yam (Dioscoreaceae)
Plant group Dicotyledon Monocotyledon
Chromosome number 2n=90 (hexaploid) 2n=20
Flower character Monoecious Dioecious
Origin Tropical America (Peru, Ecuador) West Africa, Asia
Historical beginning Prehistoric 50,000 BC
Edible storage organ Storage root Tuber
Number/plant 4 to 10 1 to 5
Appearance Smooth, with thin skin Rough, scaly
Shape Short, blocky, tapered ends Long, cylindrical, some with "toes"
Dry matter 22 to 28% 20 to 35%
Mouth feel Moist* Dry
Taste Sweet* Starchy
Beta carotene (Vitamin A) High (orange vars.)* Very low
Propagation Transplants / vine cuttings Tuber pieces
Growing season 90 to 150 days (120 = Jewel) 180 to 360 days
Maturity None At senescence
Storage (Cured at 80 to 86°F) 55 to 60°F 54 to 61°F
Climatic requirements Tropical and temperate Tropical
Availability Grown in USA Imported from Caribbean

* Characteristic of most sweetpotato varieties grown in the United States


Specialist, Sweetpotato/Curcurbits/Sweet Corn
Horticultural Science

Publication date: Jan. 30, 1998

North Carolina State University and North Carolina A&T State University commit themselves to positive action to secure equal opportunity regardless of race, color, creed, national origin, religion, sex, age, veteran status or disability. In addition, the two Universities welcome all persons without regard to sexual orientation.