Are there any fern fiddles that should not be eaten?

Yes, some fern fiddles should not be eaten due to potential toxicity. For instance, the fiddleheads of the ostrich fern (Matteuccia struthiopteris) are edible, while those of the bracken fern (Pteridium aquilinum) contain carcinogenic compounds and should be avoided. It's crucial to properly identify ferns and ensure that any fiddleheads consumed are safe and prepared correctly, as some can cause gastrointestinal distress if eaten raw. Always consult reliable sources or experts before foraging for wild ferns.