This was my first year trying to grow sweet potatoes. When I harvested them, the tubers were average, to large size but most grew in the shape of "C" and many intertwined together, imagine two "C's interlocking, and I had to separate them. After curing they, have a great flavor but are a b(*tch to peel.

What caused them to curl while growing and what can I do to rectify this next year.