Bracken

Bracken(Pteridium) is agenusof large, coarsefernsin thefamilyDennstaedtiaceae. Ferns (Pteridophyta) arevascular plantsthat have alternating generations, large plants that produce spores and small plants that producesex cells(eggs and sperm). Brackens are noted for their large, highly divided leaves. They are found on all continents except Antarctica and in all environments except deserts, though their typical habitat ismoorland. The genus probably has the widest distribution of any fern in the world.
The wordbrackenis ofOld Norseorigin, related to Swedishbräkenand Danishbregne, both meaning fern.
In the past, the genus was commonly treated as having only one species,Pteridium aquilinum, but the recent trend is to subdivide it into about ten species.
Like other ferns, brackens do not have seeds or fruits, but the immature fronds, known asfiddleheads, are sometimes eaten, although some are thought to be carcinogenic.
Bracken is one of the oldest ferns, with fossil records over55 million years oldhaving been found. The plant sends up large, triangularfrondsfrom a wide-creeping undergroundrootstock, and may form densethickets. This rootstock may travel a meter or more underground between fronds. The fronds may grow up to 2.5 m (8 ft) long or longer with support, but typically are in the range of0.6–2 m (2–6+1⁄2ft) high. In cold environments, bracken isdeciduousand, as it requires well-drained soil, is generally found growing on the sides of hills.
Fernsporesare contained in structures found on the underside of the leaf calledsori. The linear, leaf-edge pattern of these in bracken is different from that in most other ferns, where the sori are circular and occur towards the center of the leaf.
Pteridium aquilinum(bracken or common bracken) is the most common species with acosmopolitan distribution, occurring intemperateandsubtropicalregions throughout much of the world. It is a prolific and abundant plant in the moorlands of Ireland, where it is limited to altitudes of below 600 metres. It does not like poorly drained marshes or fen. It has been observed growing in soils frompH2.8 to 8.6. Exposure to cold or high pH inhibits its growth. It causes such a problem in invading pasturelands that at one time the British government had an eradication programme. Special filters have even been used on some British water supplies to filter out the bracken spores.
Bracken is a characteristic moorland plant in Ireland which over the last decades has increasingly out-competed characteristic ground-cover plants such asmoor grasses,cowberry,bilberry, andheathers, and now covers a considerable part of upland moorland.
Once valued and gathered for use in animal bedding, tanning, soap and glass making, and as a fertiliser, bracken is now seen as a pernicious, invasive, and opportunistic plant, taking over from the plants traditionally associated with open moorland and reducing easy access by humans. It is toxic to cattle, dogs, sheep, pigs, and horses, and is also linked to cancers in humans.It can harbour high levels of sheep ticks, which can pass onLyme disease. Grazing provided some control by stock trampling, but this has almost ceased since the2001 foot-and-mouth disease outbreakreduced commercial livestock production. Global climatic changes have also suited bracken well and contributed to its rapid increase in land coverage.
Bracken is a well-adapted pioneer plant which can colonise land quickly, with the potential to extend its area by as much as 1%–3% per year. This ability to expand rapidly at the expense of other plants and wildlife can cause major problems for land users and managers. It colonises ground with an open vegetation structure, but is slow to colonise healthy, well managed heather stands.
Bracken presents a threat to biodiversity. Many plant species occur only on upland moorland, tied to unique features in the habitat. The loss and degradation of such areas due to the dominance of bracken has caused many species to become rare and isolated.
Evolutionarily, bracken may be considered one of the most successful ferns. It is considered highlyinvasive, and can survive inacid soils.
Woodlandfungisuch asMycena epipterygiacan be found growing under the bracken canopy. BothCamarographium stephensiiandTyphula quisquiliarisgrow primarily from dead bracken stems.
Bracken is known to produce and releaseallelopathicchemicals, which is an important factor in its ability to dominate other vegetation, particularly in regrowth after fire. Its chemical emissions, shady canopy, and thick litter inhibit other plant species from establishing themselves – with the occasional exception of plants which support rare butterflies. Herb and tree seedling growth may be inhibited even after bracken is removed, apparently because active plant toxins remain in the soil.
Bracken substitutes the characteristics of a woodlandcanopy, and is important for giving shade to European plants such ascommon bluebellandwood anemonewhere the woodland does not exist. These plants are intolerant to stock trampling. Dead bracken provides a warm microclimate for development of the immature stages.Climbing corydalis,wild gladiolus, andchickweed wintergreenalso seem to benefit from the conditions found under bracken stands.
The high humidity in the stands helps mosses survive underneath, includingCampylopus flexuosus,Hypnum cupressiforme,Polytrichum commune,Pseudoscelopodium purumandRhytidiadelphus squarrosus.
Brackenfiddleheadshave been eaten by many cultures throughout history, either fresh, cooked, or pickled.Pteridium aquilinumis especially common inEast Asiancuisine.
In Korea, bracken (sometimes referred to as 'fernbrake' in Korean recipes) is known asgosari(고사리), and is a typical ingredient inbibimbap, a popular mixed rice dish.Stir-fried bracken (gosarinamul) is also a common side dish (banchan) in Korea.
In Japan, bracken is known aswarabi(わらび), and is steamed, boiled, or cooked in soups.Warabimochibracken jelly, named after its resemblance tomochirice cakes, is a popular traditional dessert, although commercial variants are often made with cheaperpotato starchinstead.  The fiddleheads are also preserved in salt,sake, ormiso.
In China, bracken is known asjuecai(蕨菜), and is eaten like vegetables or preserved by drying. Also called "fernbrake", it is used as a vegetable in soups and stews.
Brackenrhizomescan be ground into flour to make bread. In theCanary Islands, the rhizome was historically used to make a porridge calledgofio.Both fronds and rhizomes have been used to produce beer in Siberia, and among indigenous peoples of North America.
Bracken leaves are used in the Mediterranean region to filter sheep's milk, and to store freshly madericottacheese.
P. esculentumrhizomes were traditionally used by theMāori peopleof New Zealand as a staple food, and are known asaruhe. They were eaten by exploring or hunting groups away from permanent settlements. The plant was widely distributed across New Zealand as a result of prehistoric deforestation, and planting on rich soils, which produced the best rhizomes. The rhizomes were dried, and could be heated and softened with a pounder (patu aruhe),after which the starch could be sucked from the fibers.Patu aruhewere important ritual items, and several distinct styles were developed.
Green bracken ferns average 25%potashand can contain as much as 55%.It has advantages over other sources of plant ash, such as hardwood, due to its high potash yield as a percentage of both dry and fresh mass, abundance, growth rate, and ease of harvesting.Bracken has been recognized as a source of potash since at least the 10th century AD, with numerous references in European texts, typically in relation to its use for soap and glass making.The turn to mined sources of potash in the industrial age ended significant use of bracken as a source of potash, contributing to its status as a troublesome weed.
Bracken has traditionally been used for animal bedding, which later breaks down into a richmulchthat could be used as fertilizer. It is still used this way inWales.It is also used as a winter mulch, which has been shown to reduce the loss ofpotassiumandnitrogenin the soil, and to lowersoil pH.
Bracken contains thecarcinogeniccompoundptaquiloside, which causes damage to DNA, thus leading to cancers of the digestive tract.Highstomach cancerrates are found inJapanandNorth Wales, where bracken is often eaten, but it is unclear whether bracken plays a role.Consumption of ptaquiloside-contaminated milk is thought to contribute to human gastric cancer in the Andean states ofVenezuela.Thesporeshave also been implicated as carcinogens.
However, ptaquiloside is water-soluble and destroyed in heat (by cooking) and alkaline conditions (by soaking).Korean and Japanese cooks have traditionally soaked the shoots in water andashto detoxify the plant before eating.Ptaquiloside also degenerates at room temperature, and denatures almost completely at boiling temperature.Despite this, moderation of consumption is still recommended to reduce chances of cancer formation.The British Royal Horticultural Society recommends against consumption of bracken altogether, by both humans and livestock.
Ptaquiloside has been shown to leach from wild bracken plants into the water supply, which has been implicated in high rates of stomach and oesophageal cancers in areas with high bracken growth, such as Wales and South America.
Uncooked bracken also contains theenzymethiaminase, which breaks downthiamine(vitamin B1). Excessive consumption of bracken can lead to vitamin B1 deficiency (beriberi), especially in animals with simple stomachs.Ruminantsare less vulnerable because they synthesize thiamine.
Ptaquiloside from bracken has been shown to becarcinogenicin some animals.Animals may ingest the plant when other sources of food are unavailable, such as during droughts or after snowfalls.
In cattle, bracken poisoning can occur in acute and chronic forms, acute poisoning being the most common. Milk from cows that have eaten bracken may also contain ptaquiloside, which is especially concentrated inbuttermilk.In pigs and horses, bracken poisoning induces vitamin B1 deficiency.
Hydrogen cyanideis released by the young fronds of bracken when eaten by mammals or insects.Two major insectmoultinghormones, alphaecdysoneand 20-hydroxyecdysone, are found in bracken. These cause uncontrollable, repeated moulting in insects ingesting the fronds, leading to rapid death.Bracken is currently under investigation as a possible source of newinsecticides.
Many sites have archaeological remains dating from theNeolithicandBronze Agesthrough to theIndustrial Revolution. The root systems of established bracken stands degrade archaeological sites by disrupting thestrataand other physical evidence. These rhizomes may travel a metre or more underground between fronds and form 90% of the plant, with only the remainder being visible.
Some small level of scattered cover can provide beneficial habitats for some wildlife, at least in the UK (as given above). However, on balance, removing bracken encourages primary habitats to re-establish, which are of greater importance for wildlife. Control is a complex question with complex answers, which need to form part of a wider approach. Management can be difficult and expensive; plans may need to be about cost-effective, practical limitation and control rather than give an expectation for eradication.
All methods need follow-up over time, starting with the advancing areas first. Given the decades elapsed to arrive at the current levels of coverage on many sites, slowing or reversing the process will be also of necessity long-term, with consistency and persistence from all parties being key.
Various techniques are recommended byNatural Englandand theRSPBto control bracken either individually or in combinationRSPB Bracken management in the uplands.
Natural Englandrecommends that only Asulam can be sprayed aerially, Glyphosate requires spot treatment, e.g. using a weedwiper or knapsack spray. The toxicity of Asulam is low and has been generally highly cost-effective but its use is now restricted by the EU after 2012, at least until specific registered uses can be defined.
Selective sprays like Starane, Access, Metsulfuron 600WG, etc. work well but only if sprayed in late autumn so the rhizomes store food for winter and hence absorb the poison.
On archaeological sites, chemical control is usually required as mechanical methods may cause damage.
Any bracken control programme must be completed, or bracken will re-establish.
A Bracken Control Group was established in 2012 to provide best-practice guidance for all bracken control techniques. The Group has also been responsible for submitting an application for an Emergency Authorisation to secure the continued availability of Asulam for bracken control, following the decision not to register the product under new regulations in the EU. Registration has been re-applied for but this will not be available until 2017 at the earliest. Until re-registration is approved the Group will aim to keep Asulam available under the emergency provisions.Bracken Control Group website
Bracken is commonly referred to by local populations in the north of England as 'Moorland Scrub'.
The creature ’Bracken’ from the 2023 video gameLethal Companyis named after the plant.