Fiddlehead ferns are the edible, unfurled fronds of young ostrich ferns; they have a tightly coiled head that resembles a fiddle. You can harvest fiddlehead ferns in the spring in the Eastern United States. Fiddleheads have a flavor similar to asparagus and are rich in vitamins A and C. A 100-gram serving of raw fiddlehead ferns has 34 calories.
Fiddlehead ferns range from 1 to 2 inches in diameter. You should harvest fiddlehead ferns when they are 1 to 2 inches off the ground. Ostrich fiddlehead ferns have a brown, papery cover over the head, and the stems have a characteristic U-shaped groove. You often find fiddlheads in clusters on the banks of streams, rivers or brooks from April to May.
Fiddlehead ferns are made up mostly of water, but they also provide protein and carbohydrates. A 100-gram serving of raw fiddlehead ferns has 4.55 grams of protein, 0.4 grams of fat and 5.54 grams of carbohydrates. Adults should consume 40 percent to 60 percent of their daily calories from carbohydrates and between 46 and 56 grams of protein daily, according to the National Academies' Institute of Medicine.
Fiddlehead ferns are very high in vitamin A, a fat-soluble vitamin essential for healthy vision, immune system function and regulation of gene expression. A 100-gram serving of raw fiddlehead ferns provides 3,617 IU of vitamin A. For adults, the Institute of Medicine's upper limit daily recommendation for vitamin A equals 3,000 IU, making fiddlehead ferns an excellent source of this nutrient. Fiddlehead ferns are also an excellent source of niacin and vitamin C and a good source of riboflavin.
Fiddlehead ferns are a good source of phosphorus, a mineral that is an important structural component of cell membranes and bone. A 100-gram serving of raw fiddleheads provides 101 mg of phosphorus, which is 14 percent of the recommended daily amount for adults. Fiddlehead ferns also provide iron, a mineral essential for red-blood-cell production. A 100-gram serving of raw fiddlehead ferns has 1.31 mg of iron, which is 16 percent of the recommended daily amount for men and 7 percent for women.
Fiddlehead ferns are available seasonally at specialty markets or health food stores. Choose fiddlheads that are firm and brightly colored with no yellow or wilting. You can store fiddleheads in the refrigerator for up to two days tightly wrapped. You also can blanch and freeze fiddleheads. You can saute, steam or simmer fiddleheads or serve them raw on salads.