About Pteridium aquilinum subsp. wightianum (Wall. ex J.Agardh) W.C.Shieh
This subspecies is Pteridium aquilinum subsp. wightianum (Wall. ex J.Agardh) W.C.Shieh, a form of common bracken. Common bracken is a herbaceous perennial deciduous plant that loses all above-ground growth in winter. Its large, roughly triangular fronds grow individually upward from an underground rhizome, reaching 0.3–1 metre (1–3+1⁄2 feet) in height. The main stem (called the stipe) grows up to 1 centimetre (1⁄2 inch) in diameter at its base, and all fronds die back to ground level each autumn. The underground rhizome can grow up to 3.5 metres (11+1⁄2 ft) deep, around 5 cm (2 in) in diameter, and up to 15 m (50 ft) in length. Because bracken regrows each spring from this shared underground rhizome, it typically forms dense colonies made up of genetically identical fronds. These colonies can reach up to 650 years of age, and individual rhizomes can live up to 72 years. One colony studied by Eino Oinonen in Raakkyla, North Karelia, Finland was measured at 489 m (1,604 ft) in diameter, and estimated to be over 1400 years old based on its growth rate. At the start of the spring growing season, the rhizome produces new fiddleheads. A single rhizome’s density and spread improves its biological success when producing new growth. New growth emerges as vertical, coiled stalks covered in silver-grey hairs, which can reach a metre or more in height before unfurling into mature fronds. Bracken is native to Europe, Eastern Asia and North America, and now has an almost cosmopolitan global distribution. In the Americas, it occurs across the continental United States, and in the Canadian provinces of Ontario, Quebec, and Newfoundland. The northern edge of its range reaches southern Alaska, while it extends south to northern portions of Mexico, as well as the Greater Antilles in the Caribbean. It grows as a weed in acidic upland pastures of northwestern Europe. It can be found in pastures, deciduous woodlands, coniferous woodlands, and on hillsides, and prefers acidic soils. It is an adaptable species that readily colonizes disturbed areas, and can grow aggressively even in its native range. For example, it has invaded heather (Calluna vulgaris (L.) Hull) stands on the North Yorkshire moors in native England. In Ireland, it grows in open woodland and sandy pastures. For reproduction, bracken produces sporangia grouped into sori on the underside of its fronds. The sori are arranged in narrow brown bands, and spores develop and release over July, August and September. Common bracken contains ptaquiloside, a carcinogenic compound. Ptaquiloside causes haemorrhagic diseases in ruminants, and tumours plus haematological problems in non-ruminants. It is also correlated with higher rates of oesophageal and gastric cancer in humans. Chronic consumption of bracken is associated with squamous cell carcinomas of the upper digestive tract (UDT) in cattle (a type of ruminant), with the most aggressive and serious tumours forming in the caudal (lower) UDT. Regions with high stomach cancer rates, such as Japan and North Wales where young bracken stems are eaten as a vegetable, do not yet have confirmed confirmation that bracken itself causes the higher cancer rates, as the increase could be attributed to other factors. Consumption of milk contaminated with ptaquiloside is thought to contribute to human gastric cancer cases in the Andean states of Venezuela. Bracken spores have also been implicated as carcinogens, and consuming contaminated water or meat may also be dangerous. However, ptaquiloside is water-soluble, so its levels can be greatly reduced by soaking bracken in cool water. Korean and Japanese cooks have traditionally soaked bracken shoots in water and ash to detoxify the plant before eating it. Ptaquiloside also degenerates naturally at room temperature, which is why toxicology studies on rats use the toxin stored at −20 °C (−4 °F). Almost all of the carcinogen denatures completely at boiling temperature. Salt and baking soda also help to volatilize the chemical. Selenium supplementation has been suggested as a way to both prevent and reverse the immunotoxic effects caused by ptaquiloside from Pteridium aquilinum. Despite its confirmed toxicity, P. aquilinum is the fifth most widely distributed common weed species in the world, and it has a long history of human consumption across many regions. Its toxicity and widespread distribution have led to varied cultural attitudes toward eating the plant. In the United Kingdom, where P. aquilinum grows very successfully, the rhizome was eaten during and after World War I. However, the Royal Horticultural Society now explicitly advises against eating bracken due to its toxicity. Bracken is widely eaten as a vegetable in Korea, Japan, the Russian Far East, and parts of China, where it has historically been one of the most important wild vegetables consumed. When people from these cultures have immigrated to new regions, they have been able to source bracken locally due to P. aquilinum's global ubiquity. In Korea, bracken is called gosari. It is soaked, parboiled, stir-fried, and commonly served as a side dish called namul. It is also a classic ingredient in the dish bibimbap. In Japan, bracken is called warabi (蕨, ワラビ), and a jelly-like starch made from the plant is a key ingredient in the chilled dessert warabimochi. As a type of sansai (mountain vegetable), young bracken shoots are steamed, boiled, or cooked in soups. Shoots can also be preserved in salt, sake, or miso. Bracken shoots have been used to produce beer in Siberia, and by indigenous peoples of North America. The rhizome can be ground into flour to make bread. Historically in the Canary Islands, rhizomes were used to make a porridge called gofio. In the Mediterranean region, bracken leaves are used to filter sheep's milk, and to store freshly made ricotta cheese. The name Nooksack translates to "always bracken fern place" in the Nooksack language, and the Nooksack people along with other Pacific Northwest tribes ate the plant's rhizome extensively. Young bracken fronds can be harvested easily, and should be cooked for 30 to 60 minutes before consumption. Mature bracken is toxic due to the enzyme thiaminase, and this toxicity can be destroyed by thorough cooking. Bracken should be avoided for consumption if you do not have the skill to prepare it correctly. In Finnish traditional medicine, bracken has been used as a remedy in multiple ways: Elias Lönnrot recommended using a powder made from the plant's roots to drive away maggots. A decoction of bracken was used to treat stomach problems, gout and joint pain. Bracken leaves were used as mattress filling, as it was believed to reduce rheumatic pain and drive away vermin.
