As Mikeb alluded to, the term "fiddlehead" is a generic term for any young fern frond edible or not but is is used as a common name
in reference to the "Ostrich Fern". To avoid confusion, the only way to be sure is to go with the Latin/Botanical/Scientific name. To add to the problem, many don't realize they're harvesting the improper species and sometimes plants are mislabeled.
"Many people mistakenly believe that all fern fiddleheads are edible. Because of this misconception, stories of people getting sick from fiddleheads are common, and this has caused many to steer clear of these wildlings.
There are three main species of edible ferns in North America: ostrich fern
), lady fern
), and bracken fern
). All of them are widespread and, in certain areas, abundant. For each of these species the part gathered and eaten is the young, tender shoot (called fiddleheads due to the curled tips, which resemble the top of a fiddle) found in spring and early summer. The mature fronds of all of these ferns should not be eaten."Ostrich Fern
"The fiddlehead stalks are smooth and naked of any scales or wool, but the coiled tops are full of brown papery flakes. The top side of the stalk (or, the part facing the center of the rosette) has a deep, U-shaped trough running its entire length – this is an important feature to look for.
Gather the fiddleheads in mid to late spring; they’ll be too old by the time the leaves are fully formed on the sugar maples and oaks. Harvest them when they are eight to twenty inches tall – as long as they are still tender and the leafy portion of the frond is not yet unfurled. Usually the bottom quarter or so of the stalk is too tough to eat; in time you’ll get the hang of knowing where to break them off. You don’t have to cut the fiddleheads; when bent they should snap off cleanly.
Many people only collect the tightly coiled tops of the fiddleheads, leaving behind the juicy stalk which constitutes the greater part of the shoot. I have never been able to figure out why this is done – there is no gustatory, culinary, or practical reason for it. In fact, I greatly prefer both the flavor and the texture of the stalks to that of the coiled leafy tips. Your fiddlehead patch will yield a lot more good food if you harvest the whole vegetable.
Simply boiled or steamed and served with butter like asparagus they are superb. Ostrich fern shoots are crisp and sweet when raw and make a pleasant addition to salads or can be just nibbled on a hike through the woods."Lady Fern
"Lady fern tastes much like ostrich fern, only with an added faint bitterness. It can be used similarly in cooking, but it is advisable to rub off the “hairs,” since their texture is rather unpleasant. I enjoy lady fern fiddleheads but find them less preferable to those of ostrich fern due to the flavor, smaller size, and somewhat annoying hairs."Bracken Fern
You'll often see these as an ingredient in packaged Asian veggies at your Asian grocery. "Unlike the other two ferns discussed, bracken does not grow in rosettes. Bracken stems grow singly, rising straight up from the ground with no branching and little taper for one to five feet – then the stalks suddenly split into three main forks, forming a large, roughly triangular frond that grows almost parallel to the ground. Bracken stalks are connected by a network of thin rhizomes found a few inches underground, and they often form very large colonies.
A distinctive feature of bracken is two black dots on the fiddlehead where the main branches fork; on warm days ants will be seen feeding on a substance produced by these dark spots. Bracken shoots are covered with a layer of short, rusty-colored fuzz which can easily be rubbed off before consumption. These fiddleheads should be collected when they are eight inches to two feet tall – as long as the forks are still unfurled and the stems snap easily. The lower portion will generally be too tough to eat, especially on the taller stalks. The season of harvest for these fiddleheads is long, as a few shoots will come up into midsummer."
"In some areas ostrich fern has been seriously overharvested by market collectors. Although they are prolific and vigorous, any of these ferns can be overcollected due to carelessness. For lady and ostrich ferns, collect only 2-5 shoots per rosette, and never more than once per season. For bracken fern, never pick more than 50 % of the stems in an area, and try to spread out your impact."http://tracksandtrees.com/articles/fiddlehead.html