Dioscorea elephantipes (CHOICE):

Related to the yam, Dioscorea elephantipes is the world’s most special potato. Some extremely old plants in habitat have been recorded reaching up to 7 feet in diameter.  Although most Dioscorea in cultivation are much smaller, they are no less impressive—shooting off a vine that grows faster than you can water it. Because this species was almost harvested to extinction in the 1950s, and due to the fact that it grows very slowly, a specimen this large is a serious statement piece for collectors in-the-know. 
A perfect windowsill plant. 

These are currently growing in 5 inch pots.

Two are available

U.S. SHIPPING ONLY
Plants ship bare root, pot/soil not included