In Maine we used to pick "fiddlesticks" behind our house and have them as a vegetable. They are a type of fern that grow near water and curl up to look like the head of a violin. You clean them by wacking them against your finger and making them uncurl momentarily, releasing the gunk inside, then boil them and serve with butter. I don't know where else they grow, but I've never heard of anyone else eating them outside of Maine.