Do not refrigerate or freeze uncooked potatoes as this will change potato starches into sugar. This alters the taste of potatoes and causes the flesh to darken when cooked.
Prolonged exposure to light causes greening and makes the potato taste bitter. Peel or pare green area from the potato before using.
There are no true "yams" commercially marketed in the United States. Product labeled as yams are really sweeter varieties of sweet potato. You can tell the difference between what we call yams and sweet potatoes by color. Sweet potatoes are colored similarly to true potatoes, while yams are darker and more vibrantly colored.
Sweet potatoes and yams come from different species of plant in the family of morning glories, originating in separate corners of the world. What we commonly eat are sweet potatoes, which are native to the American tropics. True yams, which are native to Africa, weigh between two and eight pounds and have white to yellow flesh. Sweet potatoes, on the other hand, are generally yellow to deep orange.
How potatoes came to North America is the subject of several conflicting legends. One creditable source reports that some of the first plantings were those started in New Hampshire, from stock brought from Ireland. The present name came about as an accident, having derived from the Spanish "patata," meaning sweet potato.