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.
FactorSweet PotatoYam
Scientific nameIpomoea batatasDioscorea Species
Plant FamilyMorning Glory ConvolvulaceaeYam (Dioscoreaceae)
Plant GroupDicotyledonMonocotyledon
Chromosome number2n=90 (hexaploid)2n=20
Flower characterMonoeciousDioecious
OriginTropical America(Peru,Ecuador)West Africa,Asia
Historical beginningPrehistoric50,000 BC
Edible storage organStorage rootTuber
Number/plant4-101-5
AppearanceSmooth, with thin skinRough, scaly
ShapeShort, blocky, tapered endsLong, cylindrical,some with “toes”
Dry Matter22-28%2-35%
Mouth feelMoist*Dry
TasteSweet*Starchy
Beta carotene (Vit.A)High (orange vars.)*Very low
PropagationTransplants/vine cuttingsTuber pieces
Growing season90-150 days180-360 days
MaturityNoneAt senescence
Storage(Cured at 80-86F) 55-60F.54-61 F.
Climatic requirementsTropical and temperateTropical
AvailabilityGrown in USAImported from Carribean