Athyrium niponicum (Mett.) Hance var. pictum (Maxwell) Fraser-Jenk. Woodsiaceae. Japanese Painted fern. Hardy fern. Distribution: Japan. Young fronds are boiled and eaten in Japan. However after the discovery of thaiminases in certain ferns Pteridum aquilum (bracken), Marsilea drummondii and Cheilanthes sieberi cautions are given regarding the risk of thiaminase in all ferns. It can be mostly removed by boiling, but otherwise causes vitamin B1 (thiamine) deficiency and beriberi in a matter of weeks. Eating Bracken fern also causes cancer, as do the spores, but I could find no report of other ferns being toxic. Photographed in the Medicinal Garden of the Royal College of Physicians, London.

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Athyrium niponicum (Mett.) Hance var. pictum (Maxwell) Fraser-Jenk. Woodsiaceae. Japanese Painted fern. Hardy fern. Distribution: Japan. Young fronds are boiled and eaten in Japan. However after the discovery of thaiminases in certain ferns Pteridum aquilum (bracken), Marsilea drummondii and Cheilanthes sieberi cautions are given regarding the risk of thiaminase in all ferns. It can be mostly removed by boiling, but otherwise causes vitamin B1 (thiamine) deficiency and beriberi in a matter of weeks. Eating Bracken fern also causes cancer, as do the spores, but I could find no report of other ferns being toxic. Photographed in the Medicinal Garden of the Royal College of Physicians, London. Dr Henry Oakeley. Attribution 4.0 International (CC BY 4.0). Source: Wellcome Collection.