Fern Foods of Japan and the Problem of Toxicity

Abstract

As much as any other people the Japanese appreciate and continue to utilize a variety of their native wild plants as specialty foods. The suitability of a number of species of their rich island flora for emergency food must have been learned in earliest times. This knowledge culminated in the production of so-called famine herbals, which were illustrated books describing wild plants that could serve as food in periods of scarcity. Such herbals appeared in Japan principally in the 17th and 18th centuries (Bartlett & Shohara, 1961). The fact that the Japanese have been essentially the exclusive occupants of their archipelago for centuries also helps to explain the widespread knowledge of native plants and their uses which persists even today in that very modern and highly industrialized nation. In contrast, in the United States where urbanization has been the rule, the familiarity and use of edible wild plants that formerly existed is rapidly being reduced to book knowledge. A recent residence in Japan (19661970) demonstrated to me that a surprising number of native edible plants are still known and harvested for food in rural Japan. These are not only used locally, but are made available, often in modem packaging, to urban residents either in specialty food shops in the major cities or more frequently at small tourist centers or spas that exist throughout the islands. Among the best known and most popular of wild vegetable foods are the tender croziers of certain ferns. Most common are those of the cosmopolitan and weedy Bracken (Pteridium aquilinum var. latiusculum), called in Japanese. Croziers of the native Royal Fern (Osmunda japonica) known as Zenmai are also appreciated. Although several other species of Osmunda having esculent croziers are native to Japan, including 0. asiatica (the Asiatic equivalent of O. cinnamomea) and 0. claytoniana, no reference is known to me of their use in that country. This seems curious, for the young shoots of both the Cinnamon Fern and the Interrupted Fern of North America have been recorded as edible (Stone, 1903). In one or another of its varieties the ubiquitous Bracken has been used as an occasional wild food source in many parts of the world and especially in Japan. Sturtevant has summarized these uses (see Hedrick, 1919). In Japan the fiddleheads or croziers of Bracken have probably been long used as a green vegetable in spring and were noted as edules by Thunberg (1784). Additionally, the rhizomes of this species are sometimes dug for the production of starch for food or for making paste (Takashima, 1964). Most Japanese are familiar with Warabi croziers as a specialty food, although perhaps they are unaware of the possible toxicity of these shoots as reported below. According to Takashima (1964), selections of wild Bracken having superior food quality were made during the last decade of the past century and these