Fiddleheads, an early spring delicacy in Maine, are the young coiled leaves of the ostrich fern (Matteuccia struthiopteris). Nearly all ferns have fiddleheads, but those of the ostrich fern are unlike any other. Ostrich fern fiddleheads, which are about an inch in diameter, can be identified by the brown papery scale-like covering on the uncoiled fern, as well as the smooth fern stem, and the deep ”U”-shaped groove on the inside of the fern stem. From the University of Maine Extension Service.