While emptying a pot of mixed annual flowers, my husband discovered what looked like radishes in the soil. I put them in the sink in the garage to clean off later and further investigate. Remembered them many hours later, brushed them off and sliced off a sliver to taste and was surprised that it didn't taste sharp like a radish, but like a raw potato, so I nuked the crop and found they were sweet! Further investigation told me they were probably Japanese sweet potatoes which are described as red skinned and white fleshed as those we had found. The mystery is, how did they get there?
The answer: They were from the sweet potato vine that was in the planter. It was quite pretty! A friend told me she pulled the vines out of her planters every year. I had been wondering what the ivy shaped leaves were.