Yam: All About This Understated Nutritious Tuber

Yam is the name we use to describe several plant species from the genus Dioscorea from the family Dioscoreaceae. People grow them for their edible tubers, quite like sweet potatoes. People in the United States, also call sweet potatoes with yellow flesh yams, even though the two are entirely different species from two separate families.

So if it’s not sweet potato, what is the yam plant, where it grows, and its different uses? Let’s explore this understated vegetable and see what it has to offer.

Yams are perennial herbaceous vines people grow as a staple in temperate and tropical regions for their starchy tubers. They’re native to both hemispheres’ warm areas and are currently cultivated extensively in Africa, South America, Asia, and the Caribbean. In West Africa and New Guinea, it has been a primary food source and a part of rituals for centuries.

The tubers harvested from the plant are called ‘yams,’ and people serve them the same way as potatoes. You can boil and mash them but also serve them fried, roasted, or baked. They are excellent sources of fiber, magnesium, potassium, and antioxidants. Besides improving your blood sugar levels and improving brain health, they have many attractive health benefits to offer.

Common NameYam
Botanical NameDioscorea
Plant TypePerennial Herbaceous Vine
Size (Fully Grown)Plant Lenght Even 49 Feet (About 15 Meters)!
Sun ExposureFull Sun But It Tolerates Partial Shade As Well
Soil TypeA Deep And Loose Loam That Is Rich In Organic Matter
Soil pHFrom 5.5 To 6.5
Flower ColorYellow
U.S. Hardiness Zones3, 4, 5, 6, 7, 8, 9, 10, And 11
Native AreaTropical And Temperate Regions Of Both Hemispheres

How Many Yam Varieties Are There?

As already highlighted, the term yam defines many species in the genus Dioscorea. This genus contains over 600 species, and most of them grow in Africa. The following are some of the cultivated yam species:

  1. Air Potato
  2. Bitter Yam
  3. White Yam
  4. Lesser Yam
  5. Yellow Yam
  6. Chinese Yam
  7. Cush-cush Yam
  8. Winged, Purple, Or Water Yam

Are There Any Edible Wild Yams?

Dioscorea Hirtiflora Subsp. PedicellataLusala, lwidi, or busala, grows wild in Tropical Africa.

Dioscorea Japonica – East Asian mountain yam, Japanese mountain yam, or yamaimo, grows wild in Japan, China, Korea, and Taiwan.

Dioscorea Villosa – This species grows wild in the United States from New England to Minnesota and Ontario and south to Virginia and Texas.

Where Do Yams Originate From?: The Origins Of This Ancient Vegetable

Yam is native to many different tropical and temperate regions of the world. Indigenous people have consumed wild varieties for over centuries. Its cultivation began much later, somewhere around 3000BC independently in two different regions, West Africa and Southeast Asia.

95% of the world’s yams are still harvested in West Africa, and for this reason, this plant also dominates the agricultural industry and cultural life of that region. The New Yam Festival of the Igbo people celebrated annually throughout West Africa to celebrate the end of the rainy season depicts how they treasure the vegetable. The word ‘yam’ came from the African name ‘nyami‘ for the vegetable.

Besides Africa, yams have also been used in Southeast Asia and the Caribbean for a long time. They came to the Americas through the Portuguese and Spanish during pre-colonial times.

Yams were introduced through the borders of Brazil and Guyana and quickly spread through the Caribbean. In Papua New Guinea, the harvest and use of them are complemented by ancient rituals but also taboos.

Yam Or Sweet Potato – What’s The Difference?

The names sweet potatoes and yams are often used interchangeably and incorrectly so! Other than being a tuber vegetable, they have little in common. The botanical name for sweet potatoes is Ipomoea batatas, and they belong to the morning glory family, Convolvulaceae.

Americans aren’t the only ones that confuse the two species! The famous “purple yam” from Okinawa is actually a sweet potato. In Singapore and Malaysia, the species Colocasia esculenta, or taro, is also called “yam.”

Sweet potatoes have smoother, lighter skin with elongated, pointy edges than yams, which are often dark-skinned, scaly, and have round edges. The flesh of sweet potatoes is usually orange or yellow, while yams are cream, purple, or red.

What Does The Yam Plant Look Like?

Yams are herbaceous perennials that grow in the form of climbing or trailing vines. The vines grow quickly, extending over 49 feet (about 15 meters) in length, reaching a height of 3 to 6 inches (about 7,5 to 15 cm) above the soil level.

They are usually grown as annuals, harvesting the tubers during the first season, but some are left to continue for a few more seasons. The tubers continue growing bigger, while the vines die back at the end of each growing season and resume growing as soon as the weather is favorable.


The slender, trailing stems can be smooth or prickly, depending on the variety, and bear alternately or oppositely arranged leaves. The leaves can be heart-shaped or oval and have petioles that are similar in length to the blade. Some species also have spikes around the leaf base.


The vines bear small unisexual, yellow flowers in long clusters. While each flower may not be noticeable, the clusters are rather showy. The female flowers include three-winged ovaries that ripen into capsules that enclose many tiny seeds.


The tubers are the reason why we cultivate this plant. These below-ground portions are fleshy, starchy, swollen structures, often mistaken for the root. The plants can produce a single tuber or many tubers extending from the stolons.

These tubers can be cylindrical or lobed and have thick, dark skin, like bark. The color ranges from brown, grey, black, or pink and is often scaly, and the flesh can be off-white, purplish, or reddish. The rough skin can be difficult to peel and is usually warmed to make it easier to remove.

After removing the skin, they can be boiled and mashed, roasted, or sliced, but as a general rule, you can use them almost the same way as sweet potatoes.


In What Conditions Do Yams Grow Best In?

All yam species are easy to grow from seeds, bulbils, tubers, or cuttings. Bulbils are the small tubers that come out through the leaf axils. They’re low-maintenance crops that won’t need much attention once you grow them in well-prepared beds.

Remember to choose varieties that are well-adapted to the region for the greatest success. Here are some extra tips that will come in handy.

In What Temperature Do Yams Grow Best In?

Yams are native to tropical and subtropical climates and do best when temperatures are between 77 to 86°F (about 25 to 30°F). They won’t grow well when temperatures dip below 68°F (about 20°C) and are extremely sensitive to frost.

Soil And Sun

Most species grow best in full sun, but they’ll also tolerate partial shade. Grow them at a spot with loose, deep, well-draining soil, amended with plenty of organic matter.

Soil fertility promotes the growth of tubers, so make sure your soil is rich in nutrients, especially potassium since the element promotes bigger yields.

Water And Fertilizer

Keep your plant(s) well-watered, especially during dry periods. Mulch the soil around the plants to prevent them from drying out in hot weather. Also, side dressing them with compost or manure every few months is ideal for growing the best tubers. Or, you can also supplement them with a good, balanced chemical fertilizer at midseason.

Is It Safe To Eat / Consume Yams?

Yams are a good source of nutrients and help regulate your blood sugar levels, improve digestion, help with weight loss, but they also include some unique cancer-fighting properties.

But, it’s important to note that they should only be consumed after cooking. Certain varieties contain toxic substances that you can only get rid of by cooking them!

Once you’ve peeled and cooked them, the tubers are entirely safe and healthy for you. Let’s see if there are any other considerations regarding the consumption of yams.

Pregnant And Breastfeeding Women

Cultivated yam varieties are safe and healthy for pregnant and breastfeeding women. But, wild types and uncooked yams should be avoided.


Cooked and pureed yam is an excellent first food for your child. They’re completely safe and full of nutrients for your developing baby.

People With Allergies

Allergic reactions to yams are rare. But, if you experience symptoms, including rashes or asthma, contact a doctor.

People With Diabetes

Yams are healthy foods for diabetics. They are rich in fibers and nutrients and have a lower glycemic index than potatoes. Air potatoes have a meager count, with a GI of 34.


Some yam varieties may be toxic to pets. Bitter yam, in particular, is combined with bait to poison animals.

Featured image credit – Julio Ricco/Shutterstock.com

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