Why eat ferns?
Ferns are plants, and you can eat them just as you can eat other plants. Firstly, some ferns have historically been used to supply people with calories, including the rhizomes of bracken and some woodferns. Nowadays they might be used in a survival situation or in times of catastrophe (but see the chapter on bracken for information on its carcinogenicity).
Secondly, young spring fern shoots are easily available green vegetables with a nice texture, and, like other green vegetables, they contain vitamin C, folic acids, carotenoids, fibres etc. Dvorakova et al. (2021) found that the vitamin C and carotenoid content in ferns is similar to that of ordinary green vegetables, but ferns contain more antioxidants.
And I have some extra good news, especially if you are on a vegan diet. Fern fronds contain long-chain polyunsaturated fatty acids (LC-PUFAs) – arachidonic acid (20:4n-6, ARA), eicosapentaenoic acid (20:5n-3, EPA), sciadonic acid (5,11,14-20:3, SCA), juniperonic acid (5,11,14,17-20:4, JA) and other acids (Nekrasov et al. 2019; Nekrasov and Svetashev (2021)). LC-PUFAs are considered important nutrients due to their role in human physiology and difficulty with their iosynthesis by our bodies. The major LC-PUFAs are ARA, EPA, and docosahexaenoic acid (22:6n-3, DHA). LC-PUFAs are precursors of various signalling molecules and take part in the regulation of membrane properties. We usually obtain LCPUFAs from external sources, though some endogenic synthesis from the corresponding essential fatty acids is also possible.
Moreover, ferns are aesthetically pleasing. The fiddlehead or crozier shape gives green fern dishes a particularly interesting appearance. They also have a nice, crunchy texture, something my Chinese friends would call cui. This is what makes them so appreciated in Chinese, Japanese and Korean cuisine.
Most ferns are perennials, so they can form a wonderful part of a permaculture garden. For those not acquainted with botanical terminology – perennials are plants which, although they may lose leaves in winter, can produce new shoots in spring from their ‘permanent’ root or rhizome (underground stem), so there is no need to sow or plant them anew every year. Ostrich fern is especially suitable for temperate permaculture gardens, and vegetable fern for the tropics, as they have the best taste. Given the right conditions (semi-shaded, fertile and moist), ostrich fern can create an extensive stand in your garden for you to harvest each spring. Many ferns are shade resistant and can grow in parts of forest gardens that very few other wild vegetables are able to survive in.
Like many flowering plants, ferns and horsetails contain the enzyme thiaminase, which breaks up thiamine (vitamin B1). The frequent consumption of raw or undercooked ferns can cause beri-beri illness (vitamin B1 deficiency). Thiaminase is quite temperature stable, but its content can probably be greatly reduced by cooking and discarding the water, which is part of many traditional recipes. Moreover, the occasional consumption of tiaminase-containing plants is not dangerous. Such foods pose a problem only if they become everyday culinary ingredients.
Some ferns may contain carcinogenic agents. This is mainly the case with bracken (Pteridium), which contains ptaquilioside, one of the most carcinogenic of any natural substances known in nature. Fortunately, out of 21 fern species, mainly native Danish ferns, Rasmussen and Pedersen (2017) found the ptaquiloside to be present only in bracken and none of the other ferns. On the other hand, 19 of 31 fern species tested by chemotaxonomic methods in Japan are known to contain ptaquiloside and/or related carcinogens (Potter and Baird 2004). In my opinion we need more studies on fern carcinogenity to dispel fears abou it. The issue of bracken carcinogenicity is discussed in detail in the chapter on bracken. Here I should only mention that flour extracted from bracken rhizomes has not been found to be carcinogenic (Rasmussen 2021), and boiling the fiddleheads and discarding the water should also remove considerable amounts of the toxin but not all of it (Rasmussen 2021). Surprisingly, crosiers with no carcinogens were found in the USA (Rasmussen (2021) and New Zealnd (Rasmussen et al. 2008), indicating a potential for commercial production of ptaquiloside-free fronds.
Ferns have been consumed for millennia in many countries, and even if some studies correlate their life-long consumption with increased gastro-intestinal cancers, in my opinion the argument is weak. Occasional consumption of traditionally made fern dishes should not harm you. I cannot guarantee you will live to ninety, but I have personally eaten ferns hundreds of times. In this place I would like to quote Wilson et al. (1998):
When considering the possible harmful properties of bracken, distinguishing between the concepts of hazard and risk is useful. A hazard is a set of circumstances that may have harmful consequences; risk is the probability of harmful consequences occurring from a hazard. For example, lightning is a hazard, but the risk of being struck by lightning is very small, approximately one in ten million.
The practice of eating ferns can be called ‘pteridophagy’ (analogous to similar terms such as ‘geophagy’ – eating soil, or ‘entomophagy’ – eating insects). Where is pteridophagy found? Although there are many areas of the world where a single species of fern is or was eaten, in some regions people have specialized in eating ferns and consume more species. These are usually places with damp climates where at least for some part of the year ferns can obtain enough moisture to thrive. Here we should mention east and south-east Asia, including Indonesia and the Philippines, parts of Africa, and, in the past – New Zealand and the Pacific coast of North America. However, the inhabitants of some moist areas of the world that are rich in ferns have never eaten them. This is the case with Great Britain as well as South America. In the province of Misiones in Argentina, only one species of fern is eaten (Pecluma pectinatiformis (Lindm.) M. G. Price), whereas about 50 species are used medicinally (Keller et al. 2011). For comparison, 23 species of pteridophytes are used in the cuisine of NE India (Yumkham et al. 2017) and 26 species in Nepal (Ojha and Devkota 2021), while at least 52 species of ferns are eaten in China (Liu et al. 2012). This shows the importance of cultural factors. In some areas of the world, the edibility of ferns has never been discovered due to a distrust in green foods, known as herbophobia (Łuczaj 2008a). The Amazon, where people generally refuse to eat leaves (Katz et al. 2012), is a good example of this.
For references see my newly published book:
The book presents around 80 species of edible ferns and horsetails used across the globe. As ferns often have large geographic ranges, knowledge of them may also be useful for you when travelling to distant countries. Such issues as possible toxicity, detoxification procedures, cooking techniques and basic identification principles for ferns are also discussed.
A whole spectrum of possible fern foods is presented: from green fiddleheads in spring, starch from bracken rhizomes and the pith of tree ferns, to eating polypody fern rhizomes as a sweet snack. As ferns often have large geographic ranges, knowledge of them may also be useful for you when travelling to distant countries.
A special effort was made to encompass the edible species commonly found in North America and Europe. The book includes plenty of examples from areas in temperate and tropical Asia, where the author took part in several ethnobotanical expeditions and witnessed local people gathering ferns for food and making dishes out of them. The fascinating tradition of using ferns in New Zealand was not neglected either. The book also presents traditional fern cooking recipes from all over the world.
Writing this post I would also like to recommend a book about wild foods of Japan (Eating Wild Japan) writtinen by Winifred Bird. She shared two recipes with me and I was greatly inspired by her book containing lots of info on fern uses in Japan.