Did you know that the sweet potato was brought to the rest of the world from Saint Thomas by Columbus? I'm so glad he did.
While sweet potatoes are common in most grocery stores, yams are more difficult to find. Some international markets that carry African or Caribbean foods might have them. True yams are quite a bit larger than sweet potatoes; they can be up to the size of a man's arm. They're often cut into smaller chunks at the market.
For a detailed explanation of the difference between the two potatoes here is a site to visit.
I remember my mother putting a sweet potato in a glass with just the tip of it touching the water. She would balance the potatoes up by toothpicks resting on the edge of the glass. After a week or so, roots would form, and then she would plant the potato in a big pot. It made a lovely decoration for our porch, and I have done that here in recent years. The leaves trail out of the pot and are perfect for a hanging basket in the shade. At the end of the summer, one can then harvest a few potatoes from the pot.
Here in East Texas, the small town of Gilmer perpetuates the confusion between a yam and a sweet potato with its annual Yamboree Festival. Gilmer is one of the sweet potato capitals of the country, and we can get plenty of fresh sweet potatoes in the fall.