What is the Difference Between a Sweetpotato and a Yam? Revised 9/93 -- Author Reviewed 1/98 HIL-23A Jonathan R. Schultheis and L. George Wilson Extension Horticultural Specialists Department of HorticulturalScience North Carolina Cooperative Extension Service North Carolina State University

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

* Characteristic of most sweetpotato varieties grown in the U.S.

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