I thought I remembered seeing a post where someone was searching for Above Ground Sweet Potato. I was doing a search for something else and came across a site where it is listed.

Gary/Louisville

German Aboveground Sweet Potato  This interesting winter squash gets its name from the fact that it is shaped somewhat like a sweet potato. It can be grown either on a trellis or it can be allowed to run over the ground in a large unrestricted area. Eighteen inch fruit are six inches in diameter and tapered at both ends like a sweet potato. The squash will keep for months at room temperature and are very tasty in a number of holiday dishes. PKT (15) $2

South Carolina Foundation Seed Asasociation --- 2006 Heirloom Seed Listing

http://virtual.clemson.edu/groups/seed/newpage21.htm