They're called Dioscorea, but be VERY careful about which species you get. One species---maybe more---are horribly invasive, noxious weeds in your zone. E-mail me for more info.

You are probably talking about Dioscorea bulbifera. It's supposedly hardy in zones 8 and warmer but if you are in 7b that might be warm enough. I'm in 7a and it doesn't survive the winter here but I did keep it in a container, just in case.

Bulbifera *might* be okay in Zone 7a, but *I* wouldn't trust it in the ground, or in a container! It's those little 'air potatoes' that drop off that are so terrible! I don't know if it was bulbifera or villosa that took over my yard, but it was one of them.