“Were potatoes ever so valuable that miners paid for them with gold?”

About two years ago, I slipped a note into The Nine-Year-Old’s lunch box. It was one of those preprinted affairs with a sweet little message on the front and a bit of trivia on the back that read: “Did you know? Potatoes were once so valued for their Vitamin C content that miners traded them for gold.” I know the exact wording because it seemed so plausible and unlikely that I took a picture of the card so I could look it up one day. Two years later, today’s the day. Were potatoes ever so valuable that miners paid for them in gold?