I grow the vine in a planter so the vines have nowhere else to deposit the tubers except inside the planter. So when the time
for harvesting comes i simply tip the planter over and look for the tuber. The down side of this method is that the soil soon loses its nutrients and needs to be replaced.
I used to plant the vines directly in the ground but what happened was i got a lot of small tubers and it was really difficult to dig them out of the ground. So i thought i rather have one large tuber than 20 to 30 small ones after 3-4 months..
The leaves are also edible but if you cut away too many then the vines won't produce big tubers.