Yams vs. sweet potatoes

What’s The Difference Between Yams and Sweet Potatoes?

Cecil remarks that yams are rarely seen in North America.

This leads me to wonder if I know what a yam is, or a sweet potato for that matter.

Sweet potatoes, as I think I know them, somewhat (well, just somewhat) resemble regular Idaho potatoes on the outside, and are a sort of pale yellowish orange on the inside.

There is also the “red garnet yam”, which doesn’t resemble a potato at all, neither in shape nor in color. It is purplish on the outside and intense orange on the inside. But this is commonly seen in North America – I see them at grocery stores all the time, and often buy them. And they are never close to seven feet long! Not even five feet long! More like six to eight inches long, maybe. So this certainly can’t be the yam of which Cecil speaks. So is the “red garnet” yam actually a yam, or is that just a misnomer?

ETA: Cogito ergo spud – I think, therefore I yam.

“Yams” are an oranger variety of sweet potato (Ipomoea batatas, morning glory family) in the US. True yams are Dioscorea sp. and the texture etc. is different. They are bigger, but I don’t know what max size is but people won’t buy huge vegetables here I’ll bet anyway. You probably wouldn’t find yams outside of an ethnic supermarket.

Sweet potatoes are longer and skinnier (relatively) than Idaho potatoes. They can range from cream to orangeish. Neither them nor yams are related to regular potatoes.

“Sweet potatoes” as I think I know them are shaped about the same as “regular” Idaho potatoes. What is a “red garnet yam” then, which is the kind of “yam” I see all the time? They are red/purple on the outside, longer than potatoes and often with pointy ends that tear the plastic baggies apart, and generally rather irregular in shape. Are these just, actually, a variety of sweet potato / morning glory?

I have morning glory seedlings popping up all over my yard, BTW – the feral ones with smallish white flowers. If I dig them up, do they have some kind of tubers on their roots?

Sweet potatoes and red garnet yams are different varieties of the same exact species, genus is Ipomea. Which is the same genus (but not species) as the gorgeous blue morning glory vine. But NOT the weedy sprawling white-flowered plant also called morning glory. That is Convolvulus arvensis and a horrible scourge in many a field and garden.

This is why serious gardeners use latin nomenclature – because common names are often common to unrelated plants. And different names are often given to varieties of the same plant.

“Red Garnet Yams” are just another cultivar of the common sweet potato, as are the “Asian” sweet potatoes with purple flesh. The red and purple cultivars do have a sweeter flavor with higher moisture content, which means they don’t keep as well but make a better base for sweet dishes. Sweet potatoes are not a member of the nightshades (Solanaceae).

Although sweet potatoes are part of the “morning glory” family, the common flowering plants such as the Common Morning Glory (Ipomoea purpurea) don’t produce significant tubers any more than petunias will produce normal potatoes.


I’ve always believed that you can get a strong clue about who’s related to who in the floral world by comparing the appearance of the seeds or seed pods of plants. The weedy morning glory plants I see produce seeds and seed pods that resemble very much those of the gorgeous blue morning glory vine. If I’m not mistaken, the leaves are similar too (but I’ll have to take a closer look someday RSN).

For example, I broke open the dried and crispy shell of a Jimson Weed pod, which looks like a sea urchin on the outside, and found that it looks just like a bell pepper on the inside, from which I guessed that it’s in the nightshade family along with peppers and tomatoes. Sure enough, Wikipedia says it is.

What do your wild “morning glory” seed pods look like? I wonder if we’re talking about the same weed?

Aha, so much ignorance to fight, so little time!

We had a similar thread a while back, in which I was surprised to learn that two thirds of all known vegetables are just cultivars of cabbage (including, as a case in point, Brussels sprouts).

The answer is, “Irving Berlin wrote on both.”

Yams are big. Really big. Even the smaller varieties of yams are big. Usually when you see a yam in the store, it’s cut into a still rather large hunk. Sometimes in the US, that cut end will be sealed with wax, sometimes not.

Convolvulus and Ipomoea are closely related and do have very similar seed pods.

I eat a lot of sweet potatoes because they are low glycemic. I just assumed yams were too but now I’d better look it up.

While yams are rarely seen in North America, I have seen them in the past couple of years, but marketed under the name “ñame.”

You, me, and Linneus. It is one of the foundational tools of plant classification.

Probably they are the same weed. They are indeed in the same family as the cultivated flower called Morning Glory, different genus.

I thought he used the flower for sorting plants, like all orchids have the sexual parts fused into a single organ.

flowers and seed pods are just the same organ at a different stage.

Closely related plants often have very recognizably similar seeds or seed pods, even though all other parts of the plants, even the flowers may appear totally unrecognizably different.

I gave an example of Jimson Weed and bell peppers: Not only do the flowers look very different, but even the seed pods look quite different on the outside. Yet, the Jimson Weed seed pod and the seeds themselves look very much like a bell pepper on the inside.

Even tomatoes have some recognizable similarity to peppers, at least on the inside.

Yet, the flowers are very different. Some photos:

Jimson Weed
Bell peppers (Scroll down a ways to see pic of flowers.)

ETA: In contrast, Yucca plants and Joshua trees look [del]strikingly similar[/del] nearly identical in a great many of their parts: Leaves, Flowers, seed pods, and seeds.

Do you realize that when to stoop to sniff the sweet scent of roses or honeysuckles, or admire their visual beauty, you are admiring the plants’ genitalia?

And allergies happen when you breathe in plant spooge. Or get it in your mouth.

I refuse to believe that I am smelling that when I walk by Callery pears in bloom!

(Yup, they smell like fetid jizz).

To make the issue even more confusing…

My significant other, who is Puerto Rican (and part Taíno, as most PRs are), told me that “batata” is what they call the yam, and the “ñame” (pronounced “NYAH-may”) is nothing like a sweet potato OR what we think of as yam in the 50 States. The ñame is actually a vegetable that has white meat inside with a pasty consistency. I tried it and, though good, it tastes/feels like something in between a traditional potato and a sweet potato.

My SO also confirmed that the word “ñame” is of West African origin and probably the source of the word “yam,” which it ironically is not. According to her, “batata,” where we got the word for “potato,” is actually the yam. ARGH!!!

Google has pix of the ñame.

Any other comments on this?