Sweet Potatoes vs Yams: What’s the Difference

What’s the Difference Between a Sweet Potato and a Yam?

Though sweet potatoes and yams are often advertised in the US as the same thing. They are two different vegetables.

This confusion may stem from the US Department of Agriculture’s labeling guidelines. These require products identified as yams to also be labeled as sweet potatoes.

No wonder Americans are confused!
Some of the major differences between sweet potatoes and yams:

  1. Sweet potatoes and yams belong to two different plant classes. Sweet potatoes are a dicot and yams are a monocot. Characteristics that determine whether a plant is a monocot or a dicot include the number of embryonic seed leaves (monocots have one, dicots two), different types of root growth, and direction of leaf vein growth.
  2. Although, Sweet potatoes and yams are also from different plant families. Sweet potatoes are in the Convolvulaceae family, while yams are from the Dioscoreaceae family.
  3. The Sweet potatoes originated in Central and South America, while yams originated in Asia and Africa. Sweet potatoes have also been around since prehistoric times, while yams are much newer, originating around 50,000 BC.
  4. The sweet potato that we eat is a storage root, such as a carrot or parsnip. Yams
    are tubers, which grow underground like roots but are stems.
  5. Sweet potatoes are popular in the US for their sweet taste and high Vitamin A content. Yams have a much lower concentration of Vitamin A and are starchier.
Factor Sweet Potato Yam
Scientific name Ipomoea batatas Dioscorea Species
Plant Family Morning Glory 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 4-10 1-5
Appearance Smooth, with thin skin Rough, scaly
Shape Short, blocky, tapered ends Long, cylindrical,some with “toes”
Dry Matter 22-28% 2-35%
Mouth feel Moist* Dry
Taste Sweet* Starchy
Beta carotene (Vit.A) High (orange vars.)* Very low
Propagation Transplants/vine cuttings Tuber pieces
Growing season 90-150 days 180-360 days
Maturity None At senescence
Storage (Cured at 80-86F) 55-60F. 54-61 F.
Climatic requirements Tropical and temperate Tropical
Availability Grown in USA Imported from Carribean