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Brackens (Pteridium) are a genus of about ten species of large, coarse ferns, in the family Dennstaedtiaceae. The genus has probably the widest distribution of any fern genus in the world, being found on all continents except Antarctica and in all environments except for hot and cold deserts. Therefore it is considered to have a cosmopolitan distribution. In the past, the genus was commonly treated as having only one species, Pteridium aquilinum, but the recent trend is to subdivide it into several species.
Evolutionarily, bracken may be considered to be one of the most successful ferns. The plant sends up large, triangular fronds from a wide-creeping underground rootstock, and may form dense thickets. This rootstock may travel a metre or more underground between fronds. The fronds may grow up to 2.5 m (8 feet) long or longer with support, but typically are in the range of 0.6-2 m (2-6 feet) high. In cold environments bracken is winter-deciduous, and, as it requires well-drained soil, is generally found growing on the sides of hills.
Brackens are used as food plants by the larvae of some Lepidoptera species including Dot Moth, Gold Swift, Map-winged Swift, Orange Swift and Small Angle Shades.
Pteridium aquilinum (Bracken or Common Bracken) is the most common species with a cosmopolitan distribution, occurring in temperate and subtropical regions throughout much of the world, including most of Europe, Asia, and North America in the Northern Hemisphere, and Australia, New Zealand and northern South America in the Southern Hemisphere. It is a prolific and abundant plant in the highlands of British Isles. It causes such a problem of invading pastureland that at one time the British government had an eradication program. Special filters have even been used on some British water supplies to filter out the bracken spores.
It is a herbaceous perennial plant, deciduous in winter. The fronds are produced singly from an underground rhizome, and grow to 1-3 m tall; the main stem is up to 1 cm diameter at the base.
The plant is a known carcinogen to animals such as mice, and communities (mainly in Japan and Korea) where the young stems are used as a vegetable have some of the highest stomach cancer rates in the world . The spores have also been implicated as a carcinogen. Danish scientist Lars Holm Rasmussen released a study in 2004 showing that the carcinogenic compound in bracken, ptaquiloside or PTQ, can leach from the plant into the water supply, increasing the incidence of gastric and oesophageal cancers in bracken-rich areas .
The word bracken is of Old Norse origin, related to the Swedish word bräken, meaning fern.
Bracken fiddleheads (the immature, tightly curled emerging fronds) have been considered edible by many cultures throughout history, and are still commonly used today as a foodstuff. Bracken fiddleheads are either consumed fresh (and cooked) or preserved by salting, pickling, or sun drying. In Korea, where they are called gosari namul, they are a typical ingredient in the mixed rice dish called bibimbap.
Both fronds and rhizomes have been used to brew beer, and the rhizome starch has been used as a substitute for arrowroot. Bread can be made out of dried and powered rhizomes alone or with other flour. American Indians cooked the rhizomes, then peeled and ate them or pounded the starchy fiber into flour. In Japan, starch from the rhizomes used to be used to make confections.
The Māori of New Zealand used the rhizomes of P. esculentum (aruhe) as a staple food, especially for exploring or hunting groups away from permanent settlements; much of the widespread distribution of this species in present-day New Zealand is in fact a consequence of prehistoric deforestation and subsequent tending of aruhe stands on rich soils (which produced the best rhizomes). The rhizomes were air-dried so that they could be stored and became lighter; for consumption, they were briefly heated and then softened with a patu aruhe (rhizome pounder); the starch could then be sucked from the fibers by each diner, or collected if it were to be prepared for a larger feast. Patu aruhe were significant items and several distinct styles were developed (McGlone et al. 2005).
Bracken has also been used as a form of herbal remedy. Powdered rhizome has been considered particularly effective against parasitic worms. American Indians ate raw rhizomes as a remedy for bronchitis.
Bracken has been shown to be carcinogenic and is thought to be an important cause of the high incidence of stomach cancer in Japan, where it is eaten as a vegetable, called 蕨 （わらび-warabi). It is currently under investigation as a possible source of new insecticides.
Besides causing cancer, uncooked bracken contains the enzyme thiaminase, which breaks down thiamine. Thus, eating excessive quantities of bracken can also cause beriberi, especially in creatures with simple-stomachs. Ruminants are less vulnerable because they synthesize thiamine.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Bracken". A list of authors is available in Wikipedia.|