I've never really eaten fiddleheads before. My mother liked and ate them occasionally, though mostly from frozen, as they were hard to find fresh. This past weekend, the Square One Farmer's Market opened, and one vendor was selling some, so we decided to finally take the plunge and see whether what I had heard, that they were good tasting, was true. I thought that they come out in early Spring, but perhaps it's mid to late Spring (mid May to early June).
Fiddleheads are the curled edible shoots of the ostrich fern, and are supposed to taste like a combination of asparagus and green beans. You need to cook them before eating; eating them raw will likely cause you to be ill, so be cautious.
Warning aside, it's relatively easy to cook fiddleheads. First, cut off any black parts at the end, and remove any brown husks with your fingers. Then, clean them several times in changes of water (and dispose of this water). Boil them for 12-15, or steam them for 10-12 minutes (disposing of the water). You can then use them in any way you like, in a recipe that you have that has asparagus, for example, in stir-fries (which is what we did and see there), really any vegetable dish.
They tasted quite different than anything I've eaten before, but interesting, and I would like to try them again when Spring rolls around again.