My mother, Elva, grew up on the border between Maine and New Brunswick, Canada. Back in those early years of the 20th century, people ate whatever was in season or raised locally, for the most part. After a long northeastern winter of eating the canned vegetables that had been "put up" the previous spring and summer, the earliest wild spring greens--fiddleheads and dandelion greens--were coveted by the fresh vegetable-craving rural folk.
Fiddleheads are the young coiled leaves of the Ostrich Fern, and they are practically the first green sign of spring in New England, along with the bright yellow skunk cabbage. When we lived in New Hampshire, we could find them coming up back by the old stone wall. My mother tried to time her visits to us from California to coincide with the arrival of the fiddleheads, even though this meant that she mainly saw us during mud and black fly season.
I believe that when we were out picking those little greens my mother was thinking back to how her mother showed her how she had found the best fiddleheads on the farm in Maine when she was a child. When you consider it, that means three centuries--19th, 20th, and 21st--of fiddlehead memories.
The University of Maine Cooperative Extension Service has a very nice page (from which the above photo was borrowed) on fiddleheads, what they look like, when and where to find them, and how to cook them.
If you live in a part of the country where fresh fiddleheads aren't available, you might find them in the frozen food section, but the experience just won't be the same. No black fly bites, for example...