Fiddleheads or fiddlehead greens are the furled fronds from a fledgling fern,^[1] harvested for use as a vegetable.

Left on the plant, each fiddlehead would unroll into a new frond (circinate vernation). As fiddleheads are harvested early in the season, before the frond has opened and reached its full height, they are cut fairly close to the ground.^[2]

Fiddleheads from brackens contain ptaquiloside, a compound associated with bracken toxicity, and thiaminase.^[3] Not all species contain ptaquiloside, such as Diplazium esculentum, a fern with fiddleheads regularly consumed in parts of East Asia, which differs from bracken (Pteridium aquilinum).^[4]

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 bishops, which has its origins in the shepherd's crook.