Mistaken identity: Sweet Potatoes and Yams

Sweet potato vines trailing out of the raised bed

Is it a Yam or a Sweet Potato?

For decades people have been made to think they're eating yams, when most likely they are eating sweet potatoes. So where did all the confusion start? well to understand that, it helps to understand something about sweet potatoes. There are two basic varieties of sweet potatoes; firm and soft. Their description tell us about how the particular variety holds up to heat, for instance firm sweet potatoes remain firm when cooked; whereas soft variety get soft and moist. It's possible the mix-up all began when the Guinean word "nyami" which means "to eat" was chosen by European shippers, since African slaves already been referring to the soft sweet potatoes that way since it resembled a similar tuber they ate in Africa .

Yams

However there is no relationship between the yam and the sweet potato. The yam is a member of the family Discorea spp. family, related to lilies and is native to Southeast Asia the Pacific Islands South America and Africa. However,  95% of true yams come from Africa and has been a historically important food staple to 100 million people in a harsh humid and subhumid tropic. True yams come in as many as 600 species and can vary in size ranging from a small potato of a few inches to 8 feet long. To recognize a true yam, it must have a thick, rough, bark-like exterior with the raw flesh that's moist, soft and sticky. When cooked they are not as sweet as sweet potatoes, or what Americans mistake as yams. True yams have a high starch content, very little protein and is somewhat bland. They're rich in carbohydrates various minerals and vitamins however. Raw yams contain a toxic substance dioscorine which is destroyed when cooked.  Some variety of yams are so toxic they were once used to poison the tips of arrows.

Sweet Potatoes

The sweet potato on the other hand is from the Ipomena batatas family which is related to morning glory flower. To recognize a sweet potato look for an exterior skin color of red purple yellow brown or white and is then an edible. The interior raw flesh comes in range of colors from white, yellow, orange or purple!

Nutritionally, the two are pretty on par with one another:

So why are we still confused about what were eating here in the US?! The USDA continues to label the orange flash sweet potatoes as yams to distinguish between their brown counterparts. Yet the Department of Agriculture requires any potatoes labeled as yams be accompanied by the word sweet potato. So unless you shop at an international grocer, those yams you think you're buying may actually be sweet potatoes. Be aware that even if you local grocer uses the label "yam", there are probably mislabeling it.  It helps to know exactly what you are looking for.

Okinawan Purple
New Jersey Yellow
Sweet Potatoes

To know for certain what you're eating, they always recommend grow your own particularly since it gives you more options. We were so successful last summer going sweet potatoes we have already does. We definitely plan to grow the delicious New Jersey Yellow again. These made for a scrumptious whipped sweet potatoes at our Thanksgiving dinner. This year will add varieties like Centennial, Georgia Jets and White Yam.

Sweet potatoes are easy to grow, particularly in a warmer climate. However, last summer we were able to enjoy a nice healthy harvest despite a relatively cool summer where temperature is reached over 90 for only a handful of days. We grew two varieties of sweet potatoes in one 3X6 bed and part of another 3 x 6 bed, here in our Connecticut backyard (Zone 6).   The nice things about sweet potatoes to is that they will continue to grow until you have a frost.  We dug ours up last season sometime after we had our first light frost.  This year we will plant them in two different larger beds than last year, employing crop rotation, so that soil borne illnesses don't build up.

If you want to add sweet potatoes into the garden, we highly recommend starting with slips otherwise known as little plants in a raised bed. Look for slips from reliable plant source such as your local garden center or a seed catalog, such as Park Seed. Be sure the raised bed is a good 8 inches deep and is well drained. The drought tolerant plants only need consistent watering while establishing young plants. Sweet potatoes need full sun and prefers a lot of warmth. A good way to preheat the soil, we recommend placing some black plastic mulch down a few weeks previous just planting to help warm up the raised bed.  Sweet potatoes don't have any pest problems with the exception of deer who will devour the foliage.

Okinawan Purple Sweet Potatoes

So now you don't have to be a victim of yam mistaken identity. Know what to look for when your in the market or as we always recommend grow your own. 

*Source material includes:

Northeast: fruit and vegetable gardening plant, grow up and eat the best edibles for north east gardens by Charles Nardozzi

50 Plants that Changed the Course of History by Bill laws 

Library of Congress.gov