Check wikipedia. Most of the variants of both species native to North America produce edible roots. The Sweet Potato is a member of the Morning Glory family. Each plant produces more than 10 tubers in a season. 10 year old plants can have tubers over 8' long, and, more than 2' in diameter.
LOL! I'm always glad to help others. You'd be surprised how many "Decorative" plants have 1, or, multiple edible parts. Dahlias, Cannas, Cala Lilly, and the list goes on! Ha, ha! Who needs a grociery store - just look out the window. ;-)
Is there a website? Or a book? Would make a great Christmas gift for a budding "herbalist", and "naturalist" like my Sister, she is always hard to shop for!!LOL!!
Check under Foraging guide books, or, Edible Plant/Survivalist guides. I've found several dozen through the Library. One of the best is "Edible, and, Usefule Plants of Eastern North America. It covers a wide range of plants from Iceland, all the way to FL, and, as far West as the eastern 1/3 of TX. You'll recognize a lot of the plants as common "Weeds" that you never thought of using for anything, except, possibly as a Naturalizing border. I certainly got surprised by some of them. Depending on who you ask, there are 4000 - 7000 edible plants world wide, and, at least 1/2 of them can be found here in the states. Either native, or, naturalized invasives that croud out native plants. Those you're encouraged to pull out by the roots even if you only intend to use the leaves.