Fiddlehead ferns refers to the unfurled fronds of a young fern harvested for food consumption. 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 leaf vegetable. The most popular of these are:

• Bracken, Pteridium aquilinum, found worldwide
• Ostrich Fern,Matteuccia struthiopteris, found in northern regions worldwide, and the central/eastern part 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. This can lead to beriberi and other vitamin B complex deficencies if consumed to excess or if one's diet is lacking in these vitamins.

Sources and harvesting
Though available regionally in some supermarkets and restaurants, Fiddlehead ferns remain a seasonal produce. In rural areas Fiddleheads are also harvested by individuals in early spring. When picking fiddleheads it is recommended to take no more than three tops per plant. Each shoot fruits seven tops that turn into ferns and over-picking will kill the plant. Maintaining sustainable harvesting methods is important in the propagation of any food species not farmed.

In Asian cuisine
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.

North American cooking
Ostrich fern fiddleheads are a traditional dish of New England, Québec and New Brunswick. The New Brunswick village of Tide Head bills itself as the Fiddlehead Capital of the World. In the U.S. state of Vermont fiddleheads are served with cider vinegar and butter in the spring, and pickled with dill seed for eating year round.

When cooking fiddleheads - first, remove all the yellow/brown skin, bring to a boil and remove the water; then, bring up to a boil again and cook until desired tenderness. Removing the water reduces the bitterness and reduces the content of tannins and toxins.