Fiddlehead is a name referring either to a young fern or to the top part of the fern that appears curled. The fiddlehead, or circinate vernation, unrolls as the fern matures and grows, due to more growth in the inside of the curl.
The fiddlehead resembles the curled ornamentation (called a scroll) on the end of a stringed instrument, such as a fiddle. It is also called a crozier, after the curved staff used by shepherds and bishops.
The fiddleheads of certain ferns are eaten as a cooked green. The most popular of these are:
- Bracken, Pteridium aquilinum, found worldwide
- Ostrich fern, Matteuccia struthiopteris, found in the eastern parts of North America
- Cinnamon fern or buckhorn fern, Osmunda cinnamomea, found in the Eastern parts of North America
- Royal fern, Osmunda regalis, found worldwide
- Zenmai or flowering fern, Osmunda japonica, found in East Asia
- Vegetable fern, Athyrium esculentum, found throughout Asia and Oceania
Some ferns contain carcinogens, and Bracken has been implicated in stomach cancer. Despite this, most people can eat ostrich and cinnamon fern fiddleheads without any problems. In 1994, there were several instances of food poisoning associated with raw or lightly cooked fiddleheads in New York state and Western Canada, no definitive source of the food poisoning was identified, and authorities recommended thorough cooking of fiddlehead ferns to counteract any possible unidentified toxins in the plant.
Many ferns also contain the enzyme thiaminase, which breaks down thiamine, which can lead to beriberi and other vitamin B complex deficencies if consumed to excess or if one's diet is lacking in these vitamin.
Fiddleheads have been part of traditional diets in much of Asia, Australia and New Zealand, as well as among Native Americans for centuries. In Japan, bracken fiddleheads (known locally as わらび or 蕨, warabi) are a prized dish, and roasting the fiddleheads is reputed to neutralize any toxins in the vegetable.