Sweet Potato leaves -- a source of food

I've planted sweet potatoes, plowed sweet potatoes, hoed sweet potatotes, dug sweet potatoes, eaten sweet potatoes baked, candied, with and without marsh mellows -- but until recently I didn't know the potato vines were good to eat.

Mark and Julie have as neighbors in North Carolina an elderly Japanese couple who maintain a garden of fruit trees, vegetables and flowers.   They share their produce and recently this included leaves from sweet potato plants.  Mark said the sweet potato leaves tasted much like spinach.  When we dug our potatoes we first cut off the vines and fed them to cows.  We had no idea we were giving the cows food that we could have enjoyed.