Plant terminology and nomenclature are always a bit confusing. We’re written before about the importance of scientific names for clarity and specificity, and in today’s blog we’ll be exploring yet another example. While in many parts of the US, the term “yam” and “sweet potato” are used interchangeably, in reality these are quite different plants and quite different foods. They also have their own fascinating histories, so we’ll touch on that too as we dig in and learn about the difference between yams and sweet potatoes!
Bottom Line Up Front: We’re Eating Sweet Potatoes
While you may see the word “yams” on prepared foods or canned products, the reality is that most “yams” sold in the US and Canada are more properly called sweet potatoes. We’ve discussed sweet potatoes (Ipomoea batatas) in a bit of depth before. They’re a hugely popular vegetable both for their versatility and for the wonderful flavors they bring to both sweet and savory dishes. Personally, we’re big fans—the Gardzen Test Gardens are located in North Carolina, and our state produces something like 70% of the total US sweet potato crop every year.
What are Yams?
So if most of us are actually eating sweet potatoes, what are yams?
Yams are members of the genus Dioscorea, specifically species within that genus that form edible tubers. The above ground parts of the plants are general long, leafy vines, which can grow up to 50 feet/15 meters in length depending on species, varietal, and location. The harvested tubers are generally much larger than sweet potatoes, with a rough, bark-like skin and a starchy, mealy texture. While many other species—including sweet potatoes—may sometimes be referred to as “yams”, true yams are all Dioscorea species, with D. rotundata likely being the most popular. Dioscorea rotundata is widely grown across West Africa, where it is also known as white yam, African yam, Guinea yam, or ñame. The word “ñame” is the word uses for this plant in the Fulani language. Pronounced “nyameh”, it’s the most likely source of the word ‘yam’. Yams have been cultivated around the world for thousands of years; D. rotundata has been domesticated for so long that it may have originated when the Sahara was an expanse of forest and savannah rather than a desert!
So Why Do We Call Sweet Potatoes “Yams”?
This is a really difficult question to answer definitely. The most likely reason we use the term ‘yams’ for sweet potatoes may have its roots in the Atlantic Slave Trade. Enslaved Africans were transported to the New World as forced labor in agriculture, and they may have used the word ñame to discribe sweet potatoes given the similarties between the two plants. From there, the word “ñame” became “yam” and continued on as another name for sweet potatoes in some parts of the country.
Can We Buy Real Yams?
With a little time and effort, yes! If you’d like to try real yams, you should look in specialty produce markets or in stores that specialize in West African or Latin American produce and foods. True yams are used in cuisines across West Africa in a variety of ways: they may be mashed, sliced and fried, pounded into a paste, or used in soups and stews. We don’t have the space or scope to delve into all the many recipes in which yams appear, but if you’re feeling adventerous it could be worth exploring. West Africa has a diversity of cuisines, so there’s a lot to learn! Yams also appear in Latin America, Southeast Asia, and Japan as both a staple and specialty food, so this may be a good chance to globalize your palate a bit.
Yams, Sweet Potatoes, and Our Gardens
If you live in a sub-tropical or tropical zone with a long, warm, and humid growing season, you might be able to try and grow yams at home. Yam cultivation is rare in the US due to the climate restrictions, but some gardeners have been able to make it work. We strongly recommend contacting your local extension office and asking their best advice before jumping into yam cultivation in your home garden. For the rest of us, we hope this helps everyone understand the distinction between yams and sweet potatoes and maybe sparks some curiousity to explore yams as a cooking ingredient.
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