Bracken

{{Short description|Genus of ferns}} {{Redirect|Pteridium|the Ediacaran organism|Pteridinium}} {{Other uses}} {{multiple issues|{{more science citations needed|date=May 2026}}}}{{use dmy dates|date=May 2026}} {{use British English|date=May 2026}} {{Automatic taxobox | fossil_range = Paleogene-Recent, {{Fossil range|55|0}}<ref>{{Cite journal |last=Vetter |first=János |date=2009-03-01 |title=A biological hazard of our age: Bracken fern [ Pteridium aquilinum (L.) Kuhn] — A Review |journal=Acta Veterinaria Hungarica |volume=57 |issue=1 |pages=183–196 |doi=10.1556/avet.57.2009.1.18 |issn=0236-6290}}</ref><ref>{{Cite journal |last=Gomes |first=Joana |last2=Magalhães |first2=Ana |last3=Michel |first3=Valérie |last4=Amado |first4=Inês F. |last5=Aranha |first5=Paulo |last6=Ovesen |first6=Rikke G. |last7=Hansen |first7=Hans C. B. |last8=Gärtner |first8=Fátima |last9=Reis |first9=Celso A. |last10=Touati |first10=Eliette |date=2012-03-01 |title=Pteridium aquilinum and Its Ptaquiloside Toxin Induce DNA Damage Response in Gastric Epithelial Cells, a Link With Gastric Carcinogenesis |journal=Toxicological Sciences |volume=126 |issue=1 |pages=60–71 |doi=10.1093/toxsci/kfr329 |issn=1096-6080}}</ref> | image = Pteridium_aquilinum_nf.jpg | image_caption = ''Pteridium aquilinum''<ref>painting circa 1920 by the Swedish botanist C. A. M. Lindman (1856–1928), taken from his book(s) Bilder ur Nordens Flora (first edition published 1901–1905, supplemented edition 1917–1926?).</ref> | taxon = Pteridium | authority = Gled. ex Scop. 1760 not Raf. 1814 (Pteridaceae) | subdivision_ranks = Species | subdivision = See text }}'''Bracken''' ('''''Pteridium''''') is a genus of large, cosmopolitan, coarse ferns in the family Dennstaedtiaceae. Brackens are noted for their large, highly divided fronds and are found on all continents except Antarctica; their typical habitat is moorland.The word ''bracken'' is of Old Norse origin, related to Swedish ''bräken'' and Danish ''bregne'', both meaning fern. In the past, the genus was commonly treated as having only one species, ''Pteridium aquilinum'', but the current trend is to subdivide it into about ten species. Like other ferns, brackens reproduce by spores rather than seeds or fruit. The immature fronds, known as ''fiddleheads'', are sometimes eaten, although some contain carcinogenic compounds.

==Description== {{unreferenced section|date=May 2026}} thumb|Sori (paler green) along outer edge on underside of leaves Bracken is one of the oldest ferns, with fossil records from the Eocene period 55 million years old having been found. 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 {{convert|2.5|m|ft|abbr=on|frac=2}} long or longer with support, but typically are in the range of {{convert|0.6–2|m|ft|abbr=on|frac=2}} high. In cold environments, bracken is deciduous and, as it requires well-drained soil, is generally found growing on the sides of hills.

Fern spores are contained in structures found on the underside of the leaf called sori. The sori of bracken are located in a line next to the leaf-edge and are distinctly different from those in most other ferns, where the sori are circular and occur towards the centre of the leaf.

== Species == {{refimprove section|date=May 2026}} As of this date,{{when|date=May 2026}} the following is a list of recognised ''Pteridium'' species:<ref>{{Cite web | url=http://www.theplantlist.org/tpl1.1/search?q=Pteridium | title=The Plant List, search for ''Pteridium'' | archive-url=https://web.archive.org/web/20191101214436/http://www.theplantlist.org/tpl1.1/search?q=Pteridium | archive-date=2019-11-01}}{{full|date=May 2026}}</ref>{{better source|date=May 2026}}

{{Columns-list|colwidth=30em| # ''Pteridium aquilinum'' - nearly cosmopolitan # ''Pteridium arachnoideum'' - Mexico, Central and South America, Galápagos # ''Pteridium caudatum'' - Mexico, Central and South America, Florida, West Indies # ''Pteridium centrali-africanum'' - Zaire, Zambia, Tanzania, Burundi # ''Pteridium esculentum'' - China, Southeast Asia, Australia, New Zealand # ''Pteridium falcatum'' - Guangxi # ''Pteridium feei'' - Mexico, Central America # ''Pteridium lineare'' - Yunnan # ''Pteridium revolutum'' - China # ''Pteridium tauricum'' - Caucasus # ''Pteridium yunnanense'' - Yunnan }}

==Distribution and habitat== {{copy edit|section|for=redundant content, poorly structured narrative flow, impulsive unsourced content additions|date=May 2026}} {{more science citations needed|section|date = April 2014}} ''Pteridium aquilinum'' (bracken or common bracken) is the most common species of this plant type with a cosmopolitan distribution (occurring in suitable habitats in temperate and subtropical regions throughout much of the world).{{cn|date=May 2026}}

It is a prolific and abundant plant in the moorlands of Ireland, where it is limited to altitudes of below 600 metres.{{cn|date=May 2026}} It does not like poorly drained marshes or fen.{{cn|date=May 2026}} It has been observed growing in soils from pH 2.8 to 8.6.{{cn|date=May 2026}} Exposure to cold or high pH inhibits its growth.{{cn|date=May 2026}}

As of the mid-1990s,{{update inline|date=May 2026}} the problem of the expansive growth of the range of bracken was an acute issue in Great Britain; as Malcolm Smith noted in reporting for ''The Independent'' in September 1996,<blockquote>The area covered by [bracken, as of that date] in Britain is equivalent to the size of Yorkshire, 2.5 [million] acres... [and] it is still spreading, in places by up to three per cent a year<ref name=IndependentBrackenSporeOverview/></blockquote> citing a Bracken Advisory Commission member and professor of sustainable land use.<ref name=IndependentBrackenSporeOverview/><ref>See also the {{Cite web | url=https://species.nbnatlas.org/species/NBNSYS0000002031 | title=NBN distribution map for the United Kingdom | website=species.nbnatlas.org}}{{full|date=May 2026}}{{primary source inline|date=May 2026}}</ref> That expert, Roy Brown, noted bracken to be "particularly bad in eastern Scotland, Cumbria, in the North York Moors, parts of Wales and southwest England", and "spreading on many lowland roadside verges, sometimes into pastures", noting that "In the uplands, if heather moorland is burnt too often, or grazed too heavily, bracken takes over... spread[ing] very quickly, especially on deeper soils, by its underground rhizomes", noting that once it becomes established, its eradication is difficult.<ref name=IndependentBrackenSporeOverview/> Brown stated his view, at that time, that "removing the grants that used to be paid to farmers to eradicate bracken has done us no favours".<ref name=IndependentBrackenSporeOverview/> (At one time the British government had an eradication programme, paying farmers to do so—but as of September 1996, such support had ceased, except in Wales.<ref name=IndependentBrackenSporeOverview>{{cite web| author = Smith, Malcolm | date = 21 September 1996 | title=Spores for Thought| work = The Independent (independent.co.uk) | url=https://www.independent.co.uk/arts-entertainment/spores-for-thought-1364558.html| access-date=2026-05-10}}</ref>)

Bracken is a characteristic moorland plant in Ireland,{{cn|date=May 2026}} which over the last decades{{when|date=May 2026}} has increasingly out-competed characteristic ground-cover plants such as moor grasses, cowberry, bilberry, and heathers.{{cn|date=May 2026}} It now{{when|date=May 2026}} covers a considerable part of upland moorland.{{what|date=May 2026}}{{cn|date=May 2026}} It causes problems in its invading pasturelands.{{cn|date=May 2026}} left|thumb|Bahamian Pineyards with Southern Bracken Fern at The Lucayan National Park of the Bahamas

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.{{cn|date=May 2026}} It is toxic to cattle, dogs, sheep, pigs, and horses,{{cn|date=May 2026}} and is also linked to cancers in humans.<ref>{{cite journal|last1=Potter|first1=D.M.|title=Carcinogenic effects of ptaquiloside in bracken fern and related compounds|journal=British Journal of Cancer|date=4 September 2000|volume=83|issue=7|pages=914–920|doi=10.1054/bjoc.2000.1368|pmid=10970694|pmc=2374682}}{{primary source inline|date=May 2026}}</ref>{{primary source inline|date=May 2026}} In the United Kingdom, concern over the ptaquiloside-class of oncogenic natural products has led to application of special filters in processing British water supplies, to filter out bracken spores.<ref name=IndependentBrackenSporeOverview/>

Bracken can harbour high levels of sheep ticks, which can pass on Lyme disease.{{cn|date=May 2026}} Grazing provided some control by stock trampling,{{cn|date=May 2026}} but this has almost ceased since the 2001 foot-and-mouth disease outbreak reduced commercial livestock production.{{cn|date=May 2026}}

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.{{cn|date=May 2026}} This ability to expand rapidly at the expense of other plants and wildlife can cause major problems for land users and managers.{{cn|date=May 2026}} It colonises ground with an open vegetation structure, but is slow to colonise healthy, well managed heather stands.{{cn|date=May 2026}}

Bracken presents a threat to biodiversity.{{Citation needed|date=April 2014}} Many plant species occur only on upland moorland, tied to unique features in the habitat.{{Citation needed|date=April 2014}} The loss and degradation of such areas due to the dominance of bracken has caused many species to become rare and isolated.{{Citation needed|date=April 2014}}

Bracken is known to form large fern prairies (sometimes known as fern savannahs or the Fernland).{{cn|date=May 2026}}<ref>{{Cite journal |last=Ellis |first=David V. | date=2003 | title= Review: [Untitled] | format = book review | journal=Oregon Historical Quarterly |volume=104 |issue=3 |pages=140-142 |issn=2329-3780 | url = https://www.jstor.org/stable/20615351 | access-date = 2025-05-10 | url-access = registration | quote = Reviewed Work: ''Changing Landscapes: "Sustaining Traditions": Proceedings of the Fifth and Sixth Annual Coquille Cultural Preservation Conferences'' by Donald B. Ivy, R. Scott Byram}}{{failed verification|date=May 2026}}</ref>{{failed verification|date=May 2026}}<ref>{{Cite journal |last=Maguire |first=Bassett |last2=Ashton |first2=Peter S. |date=1977 |title=Systematic, Geographic and Phyletic Considerations |url=https://www.jstor.org/stable/1220033 |journal=Taxon |volume=26 |issue=4 |pages=343–368 |doi=10.2307/1220033 |issn=0040-0262|url-access=subscription }}{{primary source inline|date=May 2026}}</ref>{{primary source inline|date=May 2026}}<ref>{{Cite journal |last=McGlone |first=M. S. |date=2001 |title=The Origin of the Indigenous Grasslands of Southeastern South Island in Relation to Pre-Human Woody Ecosystems |url=https://www.jstor.org/stable/24056358 |journal=New Zealand Journal of Ecology |volume=25 |issue=1 |pages=1–15 |issn=0110-6465}}{{primary source inline|date=May 2026}}</ref>{{primary source inline|date=May 2026}}<ref name=":1">{{Cite journal |last=Huber |first=Otto |last2=Steyermark |first2=Julian A. |last3=Prance |first3=Ghillean T. |last4=Alès |first4=Catherine |date=1984-04-01 |title=The Vegetation of the Sierra Parima, Venezuela-Brazil: Some Results of Recent Exploration |journal=Brittonia |language=en |volume=36 |issue=2 |pages=104–139 |doi=10.2307/2806619 |issn=1938-436X}}{{primary source inline|date=May 2026}}</ref>{{primary source inline|date=May 2026}} Some of these are natural but others can be formed via fires created by humans.<ref name=":1" />{{primary source inline|date=May 2026}} Brackens are also key parts of other types of savannah such as Pine savannah and Pineyards.<ref>{{Cite book |last=Nickrent |first=Daniel L. |title=The Vascular Flora of Andros Island, Bahamas |last2=Eshbaugh |first2=W. Hardy |last3=Wilson |first3=Thomas K. |date=1988 |publisher=Kendall/Hunt Publishing Company |isbn=978-0-8403-4756-5 |location=Dubuque,Iowa}}{{page needed|date=May 2026}}</ref>{{page needed|date=May 2026}}

==Ecology== {{expand section | with = a proper description of the plant ecology of the species, gathering the disparate statements throughout the article already, and adding secondary and tertiary source-derived treatments to give this section proper scope|small = no|date=May 2026}} Evolutionarily, bracken may be considered one of the most successful ferns. It is considered highly invasive, and can survive in acid soils.<ref>{{cite book |author = | date = 2003 | title=Bracken and Its Management | location=Bingley, England | publisher=Sports Turf Research Institute | isbn = | url = | access-date = }}{{page needed|date=May 2026}}</ref>{{full|date=May 2026}}{{better source|date=May 2026}}

=== Fungal associations === {{unreferenced section|date=May 2026}} Woodland fungi such as ''Mycena epipterygia'' can be found growing under the bracken canopy.{{cn|date=May 2026}} Both ''Camarographium stephensii'' and ''Typhula quisquiliaris'' grow primarily from dead bracken stems.{{cn|date=May 2026}}

=== Other plant associations === {{unreferenced section|date=May 2026}} thumb|Young bracken fronds curled Bracken is known to produce and release allelopathic chemicals, 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 woodland canopy, and is important for giving shade to European plants such as common bluebell and wood anemone where 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, and chickweed wintergreen also seem to benefit from the conditions found under bracken stands.

The high humidity in the stands helps mosses survive underneath, including ''Campylopus flexuosus'', ''Hypnum cupressiforme'', ''Polytrichum commune'', ''Pseudoscelopodium purum'' and ''Rhytidiadelphus squarrosus''.

==Control== {{unreferenced section|date=May 2026}} 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 by Natural England and the RSPB to control bracken either individually or in combination  RSPB Bracken management in the uplands. * Cutting — Once or twice a year, repeatedly cutting back the fronds for at least 3 years. * Crushing/rolling — Using rollers, again for at least 3 years. * Livestock treading — During winter, encouraging livestock to bracken areas with food. They trample the developing plants and allow frost to penetrate the rhizomes. In May and June, temporary close grazing or mob stocking on small areas away from nests, particularly using cattle, horses, pigs, or ponies may crush emerging bracken fronds resulting in reduced bracken cover. Sufficient fodder will be required to prevent livestock eating the bracken. This may suit steep areas where human access is difficult and herbicide undesirable. * Herbicide — Asulam (also known as Asulox) is selective for ferns; glyphosate is not; but the latter has the advantage that the effects can be seen soon after application. They are applied when the fronds are fully unfurled to ensure that the chemical is fully absorbed. Rare ferns such as adder's tongue (''Ophioglossum vulgatum''), killarney (''Trichomanes speciosum'') and lemon-scented ferns can also be found in similar habitats and it is important that these are not destroyed in the process of bracken control. Natural England recommends 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. * Allowing plants to grow in its place, e.g., the establishment of woodland, causes shade that inhibits bracken growth. In the UK, trees, notably rowan, have done well since grazing reduced greatly after the foot-and-mouth epidemic in 2000 but young saplings struggle in high bracken. In decades to come and if permitted, tree shade cover may increase and so may reduce bracken growth, but this is both long-term and in some cases is contentious in the change it would bring to traditionally open heath or moorland, both aesthetically and as a valuable habitat. * Burning — Useful for removing the litter, but may be counter-productive as bracken is considered to be a fire-adapted species. * Ploughing — Late in the season followed by sowing seed.

Any bracken control programme must be completed, or bracken will re-establish.

<gallery> Image:Adelaarsvaren planten Pteridium aquilinum.jpg|''Pteridium aquilinum'' Image:Tylerfinvold023 bracken ferns.jpg|Fronds of bracken Image:The Dingle Peninsula, County Kerry, Ireland as seen from the south 05.jpg|Bracken fronds emerging from uncultivated land that was recently burned of heather </gallery>

==Uses== [[File:Dried Eastern brakenfern.jpg|thumb|Dried bracken bundles (''P. aquilinum'') at a food market in South Korea]]

=== Food === [[File:Senjuan_Yoshimune_warabimochi.jpg|thumb|''Warabimochi'' bracken jelly, a traditional Japanese dessert. The darker jelly on the left is made from pure bracken powder, while the lighter jelly on the right uses other starches as well.]]

Bracken fiddleheads have been eaten by many cultures throughout history, either fresh, cooked, or pickled.{{cn|date=May 2026}} ''Pteridium aquilinum'' is especially common in East Asian cuisine.{{cn|date=May 2026}}

In Korea, bracken (sometimes referred to as 'fernbrake' in Korean recipes) is known as ''gosari'' ({{CJKV|k=고사리}}), and is a typical ingredient in ''bibimbap'', a popular mixed rice dish.<ref>{{Cite news|url=http://isthmus.com/food-drink/reviews/five-star-korean-bbq/|title=I brake for fernbrake|last=Fontella|first=Amelia Cook|date=16 February 2017|work=Isthmus|access-date=19 April 2017}}</ref> Stir-fried bracken (''gosari namul'') is also a common side dish (''banchan'') in Korea.<ref>{{Cite news|url=https://www.nytimes.com/2017/02/16/dining/cafe-lily-review-bensonhurst-korean-uzbek.html|title=At Cafe Lily, the Korean-Uzbek Menu Evokes a Past Exodus|last=Mishan|first=Ligaya|date=16 February 2017|work=The New York Times|access-date=19 April 2017}}</ref>

In Japan, bracken is known as {{Nihongo|''warabi''|ワラビ}}(ja), and is steamed, boiled, or cooked in soups. ''Warabimochi'' bracken jelly, named after its resemblance to ''mochi'' rice cakes, is a popular traditional dessert, although commercial variants are often made with cheaper potato starch instead. The fiddleheads are also preserved in salt, sake, or miso.<ref name="pieroni">{{cite book |editor1-last=Prance |editor1-first=Ghillean |editor2-last=Nesbitt |editor2-first=Mark |last1=Pieroni |first1=Andrea |author-link=Andrea Pieroni (ethnobotanist) |date=2005 |title=The Cultural History of Plants |publisher=Routledge |page=35 |isbn=0-415-92746-3}}</ref>

In China, bracken is known as ''juecai'' ({{Lang-zh|t=蕨菜}}), and is eaten like vegetables or preserved by drying. Also called "fernbrake", it is used as a vegetable in soups and stews.<ref>Longmeimei cooking channel: Archived at [https://ghostarchive.org/varchive/youtube/20211211/Oy3ixwCSgZk Ghostarchive]{{cbignore}} and the [https://web.archive.org/web/20210319155122/https://www.youtube.com/watch?v=Oy3ixwCSgZk Wayback Machine]{{cbignore}}: {{Citation|title=Authentic Guizhou Special Sauerkraut with Wild Herbs and Green Vegetables| date=13 March 2021 |url=https://www.youtube.com/watch?v=Oy3ixwCSgZk|language=en|access-date=2021-06-26}}{{cbignore}}</ref>

Bracken rhizomes can be ground into flour to make bread. In the Canary Islands, the rhizome was historically used to make a porridge called ''gofio''.<ref name="pieroni"/> Both fronds and rhizomes have been used to produce beer in Siberia, and among indigenous peoples of North America.<ref name="pieroni"/><ref>{{cite book|last1=Jones|first1=David L.|title=Encyclopaedia of ferns: an introduction to ferns, their structure, biology, economic importance, cultivation and propagation|date=1987|publisher=Timber Press|location=Portland, Ore.|isbn=978-0-88192-054-3|page=[https://archive.org/details/encyclopaediaoff00jone/page/13 13]|url-access=registration|url=https://archive.org/details/encyclopaediaoff00jone/page/13}}</ref>

Bracken leaves are used in the Mediterranean region to filter sheep's milk, and to store freshly made ricotta cheese.<ref name="pieroni"/>

''P. esculentum'' rhizomes were traditionally used by the Māori people of New Zealand as a staple food, and are known as ''aruhe''. 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''),<ref name=":0">{{Cite book |last1=Lehnebach |first1=Carlos A. |url=https://www.wikidata.org/wiki/Q124332398 |title=Flora: Celebrating our Botanical World |last2=Regnault |first2=Claire |last3=Rice |first3=Rebecca |last4=Awa |first4=Isaac Te |last5=Yates |first5=Rachel A. |date=2023-11-01 |publisher=Te Papa Press |isbn=978-1-9911509-1-2 |page=310 |language=English}}</ref> after which the starch could be sucked from the fibres. ''Patu aruhe'' were important ritual items, and several distinct styles were developed.<ref>{{cite journal |author1=McGlone, Matt S. |author2=Wilmshurst, Janet M. |author3=Leach, Helen M. |year=2005 |title=An ecological and historical review of bracken (''Pteridium esculentum'') in New Zealand, and its cultural significance |url=https://newzealandecology.org/nzje/2269 |journal=New Zealand Journal of Ecology |volume=28 |pages=165–184}}</ref><ref name=":0" />

=== Source of potash === Green bracken ferns average 25% potash and can contain as much as 55%.<ref>{{cite book |last=Kourik |first=Robert |year=1986 |title=Designing and maintaining your edible landscape naturally |others=Kane, Mark |location=Santa Rosa, CA |publisher=Metamorphic Press |isbn=0-9615848-0-7 |page=268 |oclc=14258849 }}</ref> 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.<ref name=rymer1976>{{cite journal |last=Rymer |first=Julia |date=July 1976 |title=The history and ethnobotany of bracken |journal=Botanical Journal of the Linnean Society |volume=73 |issue=1–3 |pages=151–176 |doi=10.1111/j.1095-8339.1976.tb02020.x}}</ref> 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.<ref name=rymer1976/> 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.<ref name=rymer1976/>

=== Others === Bracken has traditionally been used for animal bedding, which later breaks down into a rich mulch that could be used as fertilizer. It is still used this way in Wales.<ref name="abdn.ac.uk">{{cite web |url=http://www.abdn.ac.uk/organic/organic_24.php |title=Uses for Bracken |access-date=2009-07-08 |archive-url=https://web.archive.org/web/20091212233858/http://www.abdn.ac.uk/organic/organic_24.php |archive-date=2009-12-12 }}</ref> It is also used as a winter mulch, which has been shown to reduce the loss of potassium and nitrogen in the soil, and to lower soil pH.<ref name="abdn.ac.uk"/>

==Toxicity== {{multiple issues|section = yes| {{more science citations needed|section|date=May 2026}} {{update |section|date=May 2026}} }} === In animals === The ptaquiloside family of natural products from bracken have been shown to be carcinogenic in some animals.<ref name=Evans71>{{cite journal |vauthors=Evans IA, Widdop B, Jones RS |title=The possible human hazard of the naturally occurring bracken carcinogen |journal=Biochem. J. |volume=124 |issue=2 |pages=29P–30P |date=September 1971 |pmid=5158492 |pmc=1177200 |display-authors=etal|doi=10.1042/bj1240029pa }}{{primary source inline|date=May 2026}}</ref>{{primary source inline|date=May 2026}} Foraging animals may ingest the plant when other sources of food are unavailable, such as during droughts or after snowfalls.{{cn|date=May 2026}} In cattle, bracken poisoning can occur in acute and chronic forms, acute poisoning being the most common;{{verification needed|date=May 2026}} milk from cows that have eaten bracken may also contain ptaquiloside, which is especially concentrated in buttermilk.<ref name="rasmussen"/>{{better source|date=May 2026}}

With regard to human impact, the carcinogenic ptaquilosides in bracken have been shown to cause damage to DNA, and their consumption correlates with cancer incidence, in particular, gastrointestinal cancers.<ref>{{cite journal |doi=10.1093/toxsci/kfr329 |pmid=22143989 |title=Pteridium aquilinum and Its Ptaquiloside Toxin Induce DNA Damage Response in Gastric Epithelial Cells, a Link with Gastric Carcinogenesis |journal=Toxicological Sciences |volume=126 |issue=1 |pages=60–71 |year=2012 |last1=Gomes |first1=Joana |last2=Magalhães |first2=Ana |last3=Michel |first3=Valérie |last4=Amado |first4=Inês F |last5=Aranha |first5=Paulo |last6=Ovesen |first6=Rikke G |last7=Hansen |first7=Hans C B |last8=Gärtner |first8=Fátima |last9=Reis |first9=Celso A |last10=Touati |first10=Eliette |doi-access=free }}{{primary source inline|date=May 2026}}</ref>{{primary source inline|date=May 2026}} Ptaquilosides have 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.<ref name="rasmussen">{{cite web|url=https://www.theguardian.com/society/2004/sep/09/research.science|title=The fatal fern|first=Kate|last=Ravilious|date=9 September 2004|website=the Guardian|access-date=6 April 2018}}{{better source|date=May 2026}}</ref>{{better source|date=May 2026}} Consumption of ptaquiloside-contaminated milk is thought to contribute to human gastric cancer in the Andean states of Venezuela.<ref>{{cite journal |doi=10.1002/1097-0215(200002)9999:9999<::AID-IJC1028>3.0.CO;2-H |title=Possible association between gastric cancer and bracken fern in Venezuela: An epidemiologic study |journal=International Journal of Cancer |volume=91 |issue=2 |pages=252–259 |year=2001 |last1=Alonso-Amelot |first1=Miguel E |last2=Avendaño |first2=Marisabel |pmid=11146454 |doi-access=free }}{{primary source inline|date=May 2026}}</ref>{{primary source inline|date=May 2026}}  (High stomach cancer rates are found in Japan and North Wales, where bracken is often eaten, but it is unclear whether bracken plays a role.<ref>{{cite journal|author1=I A Evans |author2=B Widdop |author3=R S Jones |author4=G D Barber |author5=H Leach |author6=D L Jones |author7=R Mainwaring-Burton |name-list-style=amp | title=The possible human hazard of the naturally occurring bracken carcinogen|journal=Biochem. J.|year=1971|volume= 124 |issue=2 |pages=29P–30P|pmid=5158492|pmc=1177200 |doi=10.1042/bj1240029pa}}{{primary source inline|date=May 2026}}</ref>{{primary source inline|date=May 2026}})

The ptaquilosides are water-soluble and destroyed in heat (by cooking) and alkaline conditions (by soaking).<ref>{{cite web|url=http://www.fs.fed.us/database/feis/plants/fern/pteaqu/all.html|title=Pteridium aquilinum|website=www.fs.fed.us|access-date=6 April 2018}}</ref> Korean and Japanese cooks have traditionally soaked the shoots in water and ash to detoxify the plant before eating.<ref name="pieroni"/> Ptaquiloside also decomposes at room temperature, and almost completely at boiling temperature.<ref name="atlantic">{{cite web|url=https://www.theatlantic.com/health/archive/2011/06/the-bracken-fern-a-natural-born-killer/241271/|title=The Bracken Fern: A Natural Born Killer?|first=Hank|last=Shaw|date=2011-06-30|website=theatlantic.com|access-date=6 April 2018}}{{better source|date=May 2026}}</ref>{{better source|date=May 2026}}

The British Royal Horticultural Society recommends against consumption of bracken altogether, by both humans and livestock.<ref>{{cite web|title=Dol Sot Bibimbap|url=http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=445|access-date=2011-12-19|archive-url=https://web.archive.org/web/20111111190952/http://apps.rhs.org.uk/advicesearch/profile.aspx?PID=445|archive-date=2011-11-11}}</ref> Moderation of consumption is recommended by some popular, non-expert publications (to reduce chances of cancer formation).<ref name="atlantic"/>{{better source|date=May 2026}} ====Thiamine breakdown==== Uncooked bracken also contains the enzyme thiaminase, which breaks down thiamine (vitamin B1). Excessive consumption of bracken can lead to vitamin B1 deficiency (beriberi), especially in animals with simple stomachs. Ruminants are less vulnerable because they synthesize thiamine.<ref>{{Cite journal |last1=Pan |first1=Xiaohua |last2=Nan |first2=Xuemei |last3=Yang |first3=Liang |last4=Jiang |first4=Linshu |last5=Xiong |first5=Benhai |date=September 2018 |title=Thiamine status, metabolism and application in dairy cows: a review |journal=British Journal of Nutrition |language=en |volume=120 |issue=5 |pages=491–499 |doi=10.1017/S0007114518001666 |issn=0007-1145|doi-access=free |pmid=29986774 }}{{primary source inline|date=May 2026}}</ref>{{primary source inline|date=May 2026}} In pigs and horses, bracken poisoning induces vitamin B1 deficiency.<ref>{{cite book |author1=Auld, RA |author2=Medd, RW |title=Weeds |publisher=Inkata Press |location=Sydney |year=1992 }}{{page needed|date=May 2026}}</ref>{{full|date=May 2026}}

=== In insects === Hydrogen cyanide is released by the young fronds of bracken when eaten by mammals or insects.<ref>{{cite journal|last=Amelot ME|first=Alonso|date=February 2005|title=Kinetics of the natural evolution of hydrogen cyanide in plants in neotropical Pteridium arachnoideum and its ecological significance|journal=Journal of Chemical Ecology|volume=31 | issue = 2|pages=315–31|doi=10.1007/s10886-005-1343-z|pmid=15856786|bibcode=2005JCEco..31..315A |citeseerx=10.1.1.517.4271|s2cid=30063246}}{{primary source inline|date=May 2026}}</ref>{{primary source inline|date=May 2026}} Two major insect moulting hormones, alpha ecdysone and 20-hydroxyecdysone, are found in bracken. These cause uncontrollable, repeated moulting in insects ingesting the fronds, leading to rapid death.<ref>{{cite journal | title= Insect Hormones: Alpha Ecdysone and 20-Hydroxyecdysone in Bracken Fern|journal= Science|volume=157 |pages=1436–1438|date=22 September 1967 |doi= 10.1126/science.157.3795.1436 |pmid= 6037858 |issue=3795|last1= Kaplanis |first1= J. N. |last2= Thompson |first2= M. J. |last3= Robbins |first3= W. E. |last4= Bryce |first4= B. M. |bibcode= 1967Sci...157.1436K|s2cid= 37746757}}{{primary source inline|date=May 2026}}</ref>{{primary source inline|date=May 2026}} As of 2008, bracken was under investigation as a possible source of new insecticides.<ref>{{cite journal |vauthors=Jbilou R, Amri H, Bouayad N, Ghailani N, Ennabili A, Sayah F |title=Insecticidal effects of extracts of seven plant species on larval development, α-amylase activity and offspring production of ''Tribolium castaneum'' (Herbst) (Insecta: Coleoptera: Tenebrionidae) |journal=Bioresour. Technol. |volume=99 |issue=5 |pages=959–64 |date=March 2008 |pmid=17493805 |doi=10.1016/j.biortech.2007.03.017 |bibcode=2008BiTec..99..959J }}{{primary source inline|date=May 2026}}</ref>{{primary source inline|date=May 2026}}

==Archaeology== {{unreferenced section|date=May 2026}} thumb|200px|Bracken in Ireland with a linear pattern running across the hillside, a possible indication of past cultivation. Many sites have archaeological remains dating from the Neolithic and Bronze Ages through to the Industrial Revolution. The root systems of established bracken stands degrade archaeological sites by disrupting the strata and 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.

==In culture== Bracken is commonly referred to by local populations in the north of England as 'Moorland Scrub'.{{citation needed|date=January 2023}}

The creature 'Bracken' from the 2023 video game ''Lethal Company'' is named after the plant.{{cn|date=May 2026}}

== See also == * List of plants poisonous to equines

== References == {{Reflist|25em}}

==Further reading== * {{cite journal |vauthors=Alonso-Amelot ME, Avendaño M |title=Human carcinogenesis and bracken fern: a review of the evidence |journal=Curr. Med. Chem. |volume=9 |issue=6 |pages=675–86 |date=March 2002 |pmid=11945131 |url=http://www.benthamdirect.org/pages/content.php?CMC/2002/00000009/00000006/0004C.SGM |doi=10.2174/0929867023370743 |archive-url=https://web.archive.org/web/20111006102621/http://www.benthamdirect.org/pages/content.php?CMC%2F2002%2F00000009%2F00000006%2F0004C.SGM |archive-date=2011-10-06 |url-access=subscription }} * {{cite journal |last1=Marrs |first1=R.H. |last2=Watt |first2=A.S. |year=2006 |title=Biological Flora of the British Isles 245: ''Pteridium aquilinum'' {{small|(L.) Kuhn}} |journal=Journal of Ecology |volume=94 |issue=6 |pages=1272–1321 |doi=10.1111/j.1365-2745.2006.01177.x |s2cid=85114338 }} * {{cite web |title=''Pteridium aquilinum'' |website=Germplasm Resources Information Network |url=http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?312948 |via=ars-grin.gov |archive-url=https://web.archive.org/web/20150924144819/http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?312948 |archive-date=2015-09-24}} * {{cite web |title=''Pteridium aquilinum'' |department=Flora Europaea |website=rbge.org.uk |url=http://rbg-web2.rbge.org.uk/cgi-bin/nph-readbtree.pl/feout?FAMILY_XREF=&GENUS_XREF=Pteridium&SPECIES_XREF=&TAXON_NAME_XREF=&RANK= }} * {{cite web |title=''Pteridium aquilinum'' |department=Flora of North America |website=efloras.org |url=http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200003325 }}

== External links == {{Commons|Pteridium aquilinum}} * [https://web.archive.org/web/20110608070303/http://homepages.caverock.net.nz/~bj/fern/pteridium.htm World fern species list — ''Pteridium''] * [https://web.archive.org/web/20020808100202/http://www.rook.org/earl/bwca/nature/ferns/pteridiumaqui.html Independent page devoted to bracken (uses older classification scheme)] * [https://web.archive.org/web/20140815035945/http://www.rspb.org.uk/ourwork/farming/advice/details.aspx?id=204253 RSPB: Bracken management in the uplands] * [https://web.archive.org/web/20080720075204/http://www.butterfly-conservation.org/downloads/47/Habitat_Advice.html Bracken for Butterflies] by Butterfly Conservation * [http://www.northernbushcraft.com/plants/bracken/notes.htm Edibility of Bracken]: Identification and edible parts of bracken

Category:Dennstaedtiaceae Category:Japanese vegetables Category:IARC Group 2B carcinogens Category:Ferns of Asia Category:Ferns of the Americas Category:Ferns of Africa Category:Ferns of Europe Category:Ferns of Oceania