Bracken (''Pteridium'') is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of large, coarse
fern
A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...
s in the
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
Dennstaedtiaceae
Dennstaedtiaceae is one of fifteen families in the order Polypodiales, the most derived families within monilophytes (ferns). It comprises 10 genera with ca 240 known species, including one of the world's most abundant ferns, ''Pteridium aquilin ...
. Ferns (Pteridophyta) are
vascular plant
Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They al ...
s that have alternating generations, large plants that produce spores and small plants that produce
sex cells
Sex is the trait that determines whether a sexually reproducing animal or plant produces male or female gametes. Male plants and animals produce smaller mobile gametes (spermatozoa, sperm, pollen), while females produce larger ones ( ova, of ...
(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 is
moorland
Moorland or moor is a type of habitat found in upland areas in temperate grasslands, savannas, and shrublands and montane grasslands and shrublands biomes, characterised by low-growing vegetation on acidic soils. Moorland, nowadays, generally ...
. The genus probably has the widest distribution of any fern in the world.
The word ''bracken'' is of
Old Norse
Old Norse, Old Nordic, or Old Scandinavian, is a stage of development of North Germanic languages, North Germanic dialects before their final divergence into separate Nordic languages. Old Norse was spoken by inhabitants of Scandinavia and t ...
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
''Pteridium aquilinum'' (bracken, brake or common bracken), also known as eagle fern, is a species of fern occurring in temperate and subtropical regions in both hemispheres. Originally native to Eurasia and North America, the extreme lightness o ...
'', 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 as ''
fiddlehead
Fiddleheads or fiddlehead greens are the furled fronds of a young fern, harvested for use as a vegetable.
Left on the plant, each fiddlehead would unroll into a new frond (circinate vernation). As fiddleheads are harvested early in the sea ...
s'', are sometimes eaten, although some are
thought to be carcinogenic.
Description and biology
Evolutionarily, bracken may be considered one of the most successful ferns. It is considered highly
invasive, and can survive in
acid soils
Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the neg ...
.
Bracken, like heather, is typically found in moorland environments, and is commonly referred to by local populations in the north of England as 'Moorland Scrub'. It is also one of the oldest ferns, with fossil records over 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 long or longer with support, but typically are in the range of high. In cold environments, bracken is
deciduous
In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, aft ...
and, as it requires well-drained soil, is generally found growing on the sides of hills.
Fern
spores
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...
are contained in structures found on the underside of the leaf called
sori. 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 centre of the leaf.
Distribution
''
Pteridium aquilinum
''Pteridium aquilinum'' (bracken, brake or common bracken), also known as eagle fern, is a species of fern occurring in temperate and subtropical regions in both hemispheres. Originally native to Eurasia and North America, the extreme lightness o ...
'' (bracken or common bracken) is the most common species with a
cosmopolitan distribution
In biogeography, cosmopolitan distribution is the term for the range of a taxon that extends across all or most of the world in appropriate habitats. Such a taxon, usually a species, is said to exhibit cosmopolitanism or cosmopolitism. The ext ...
, occurring in
temperate
In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...
and
subtropical
The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Geographical z ...
regions throughout much of the world. It is a prolific and abundant plant in the moorlands of Great Britain, 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 from
pH 2.8 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 the UK which over the last decades has increasingly out-competed characteristic ground-cover plants such as
moor grasses,
cowberry,
bilberry
Bilberries (), or sometimes European blueberries, are a primarily Eurasian species of low-growing shrubs in the genus ''Vaccinium'' (family Ericaceae), bearing edible, dark blue berries. The species most often referred to is ''Vaccinium myrtillus ...
, and
heathers
''Heathers'' is a 1989 American black comedy film written by Daniel Waters and directed by Michael Lehmann, in both of their respective film debuts. The film stars Winona Ryder, Christian Slater, Shannen Doherty, Lisanne Falk, Kim Walker, and ...
, 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 on
Lyme disease
Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the ''Borrelia'' bacterium, which is spread by ticks in the genus ''Ixodes''. The most common sign of infection is an expanding red rash, known as erythema migran ...
. Grazing provided some control by stock trampling, but this has almost ceased since the
2007 foot-and-mouth disease outbreak reduced 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.
Species
Fungal associations
Woodland
fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
such as ''
Mycena epipterygia
''Mycena epipterygia'' is a species of fungus in the family Mycenaceae of mushrooms commonly found in Europe.Gerhardt, Ewald (2006). De grote paddenstoelengids voor onderweg, Tirion uitgevers B.V., Baarn, It is commonly known as yellowleg bo ...
'' can be found growing under the bracken canopy. Both ''
Camarographium stephensii'' and ''
Typhula quisquiliaris
''Typhula quisquiliaris'', commonly known as the bracken club, is a species of club fungus in the family Typhulaceae. It produces small, white fruit bodies up to in height, each with a single distinct "head" and "stem". The head is fertile, w ...
'' grow primarily from dead bracken stems.
Other plant associations
Bracken is known to produce and release
allelopathic
Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the germination, growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have ben ...
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
Canopy may refer to:
Plants
* Canopy (biology), aboveground portion of plant community or crop (including forests)
* Canopy (grape), aboveground portion of grapes
Religion and ceremonies
* Baldachin or canopy of state, typically placed over an a ...
, and is important for giving shade to European plants such as
common bluebell
''Hyacinthoides non-scripta'' (formerly ''Endymion non-scriptus'' or ''Scilla non-scripta'') is a bulbous perennial plant, found in Atlantic areas from north-western Spain to the British Isles, and also frequently used as a garden plant. It is k ...
and
wood anemone The phrase wood anemone is used in common names for several closely related species of flowering plants in genus ''Anemonoides'', including:
* ''Anemonoides nemorosa
''Anemonoides nemorosa'' (syn. ''Anemone nemorosa''), the wood anemone, is an e ...
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
''Lysimachia europaea'' (formerly known as ''Trientalis europaea'') is a flowering plant in the primrose Family (biology), family Primulaceae, called by the common name chickweed-wintergreen or arctic starflower. It is a small herbaceous perennia ...
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
''Polytrichum commune'' (also known as common haircap, great golden maidenhair, great goldilocks, common haircap moss, or common hair moss) is a species of moss found in many regions with high humidity and rainfall. The species can be exceptiona ...
'', ''Pseudoscelopodium purum'' and ''Rhytidiadelphus squarrosus''.
Uses
Food
![Senjuan_Yoshimune_warabimochi](https://upload.wikimedia.org/wikipedia/commons/c/cf/Senjuan_Yoshimune_warabimochi.jpg)
Bracken
fiddlehead
Fiddleheads or fiddlehead greens are the furled fronds of a young fern, harvested for use as a vegetable.
Left on the plant, each fiddlehead would unroll into a new frond (circinate vernation). As fiddleheads are harvested early in the sea ...
s have been eaten by many cultures throughout history, either fresh, cooked, or pickled. ''Pteridium aquilinum'' is especially common in
East Asia
East Asia is the eastern region of Asia, which is defined in both geographical and ethno-cultural terms. The modern states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. China, North Korea, South Korea and ...
n cuisine.
In Korea, bracken (sometimes referred to as 'fernbrake' in Korean recipes) is known as ''gosari'', and is a typical ingredient in ''
bibimbap
Bibimbap
* ( , from Korean , literally "mixed rice"), sometimes romanized as bi bim bap or bi bim bop, is a Korean rice dish. The term "bibim" means "mixing" and "bap" refers to cooked rice. ''Bibimbap'' is served as a bowl of warm white rice ...
'', a popular mixed rice dish. Stir-fried bracken (''gosari
namul
Namul ( ko, 나물) refers to either a variety of edible grass or leaves or seasoned herbal dishes made of them. Wild greens are called ''san-namul'' (, "mountain namul"), and spring vegetables are called ''bom-namul'' (, "spring namul"). On t ...
'') is also a common side dish (''
banchan
''Banchan'' (, from Korean: ) or bansang are small side dishes served along with cooked rice in Korean cuisine. As the Korean language does not distinguish between singular and plural grammatically, the word is used for both one such dish or ...
'') in Korea.
In Japan, bracken is known as ''warabi'' (わらび), and is steamed, boiled, or cooked in soups. ''
Warabimochi
is a wagashi (Japanese confection) made from warabiko (bracken starch) and covered or dipped in ''kinako'' ( sweet toasted soybean flour). It differs from true ''mochi'' made from glutinous rice. It is popular in the summertime, especially in t ...
'' bracken jelly, named after its resemblance to ''
mochi
is a Japanese rice cake made of , a short-grain japonica glutinous rice, and sometimes other ingredients such as water, sugar, and cornstarch. The rice is pounded into paste and molded into the desired shape. In Japan, it is traditionally ma ...
'' rice cakes, is a popular traditional dessert, although commercial variants are often made with cheaper
potato starch
Potato starch is starch extracted from potatoes. The cells of the root tubers of the potato plant contain leucoplasts (starch grains). To extract the starch, the potatoes are crushed, and the starch grains are released from the destroyed cells. Th ...
instead. The fiddleheads are also preserved in salt,
sake
Sake, also spelled saké ( ; also referred to as Japanese rice wine), is an alcoholic beverage of Japanese origin made by fermenting rice that has been polished to remove the bran. Despite the name ''Japanese rice wine'', sake, and indee ...
, or
miso
is a traditional Japanese seasoning. It is a thick paste produced by fermenting soybeans with salt and ''kōji'' (the fungus ''Aspergillus oryzae'') and sometimes rice, barley, seaweed, or other ingredients. It is used for sauces and spread ...
.
In China, bracken is known as ''juecai'' (蕨菜), and is eaten like vegetables or preserved by drying. Also called "fernbrake", it is used as a vegetable in soups and stews.
Bracken
rhizome
In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...
s can be ground into flour to make bread. In the
Canary Islands
The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Morocc ...
, the rhizome was historically used to make a porridge called ''gofio''.
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 made
ricotta
Ricotta ( in Italian) is an Italian whey cheese made from sheep, cow, goat, or Italian water buffalo milk whey left over from the production of other cheeses. Like other whey cheeses, it is made by coagulating the proteins that remain after the ...
cheese.
''P. esculentum'' rhizomes were traditionally used by the
Māori people
The Māori (, ) are the indigenous Polynesian people of mainland New Zealand (). Māori originated with settlers from East Polynesia, who arrived in New Zealand in several waves of canoe voyages between roughly 1320 and 1350. Over several ce ...
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''), after which the starch could be sucked from the fibers. ''Patu aruhe'' were important ritual items, and several distinct styles were developed.
Others
Bracken has traditionally been used for animal bedding, which later breaks down into a rich
mulch
A mulch is a layer of material applied to the surface of soil. Reasons for applying mulch include conservation of soil moisture, improving fertility and health of the soil, reducing weed growth and enhancing the visual appeal of the area.
A m ...
that could be used as fertilizer. It is still used this way in
Wales
Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...
.
It is also used as a winter mulch, which has been shown to reduce the loss of
potassium
Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...
and
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
in the soil, and to lower
soil pH
Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the neg ...
.
Green bracken ferns average 25 percent potash and can contain as much as 55 percent.
Toxicity
Bracken contains the
carcinogen
A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...
ic compound
ptaquiloside
Ptaquiloside is a norsesquiterpene glucoside produced by bracken ferns (majorly ''Pteridium aquilinum'') during metabolism. It is identified to be the main carcinogen of the ferns and to be responsible for their biological effects, such as bleedin ...
, which causes damage to DNA, thus leading to cancers of the digestive tract. High
stomach cancer
Stomach cancer, also known as gastric cancer, is a cancer that develops from the lining of the stomach. Most cases of stomach cancers are gastric carcinomas, which can be divided into a number of subtypes, including gastric adenocarcinomas. Lymph ...
rates are found in
Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
and
North Wales
, area_land_km2 = 6,172
, postal_code_type = Postcode
, postal_code = LL, CH, SY
, image_map1 = Wales North Wales locator map.svg
, map_caption1 = Six principal areas of Wales common ...
, 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 of
Venezuela
Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...
. The
spore
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...
s have 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 and
ash
Ash or ashes are the solid remnants of fires. Specifically, ''ash'' refers to all non-aqueous, non- gaseous residues that remain after something burns. In analytical chemistry, to analyse the mineral and metal content of chemical samples, ash ...
to 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 the
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
thiaminase
Thiaminase is an enzyme that metabolizes or breaks down thiamine into two molecular parts. It is an antinutrient when consumed.
The old name was "aneurinase".
There are two types:
* Thiamine pyridinylase, Thiaminase I (, )
* Aminopyrimidine ami ...
, which breaks down
thiamine
Thiamine, also known as thiamin and vitamin B1, is a vitamin, an essential micronutrient, that cannot be made in the body. It is found in food and commercially synthesized to be a dietary supplement or medication. Phosphorylated forms of thi ...
(vitamin B1). Excessive consumption of bracken can lead to vitamin B1 deficiency (
beriberi
Thiamine deficiency is a medical condition of low levels of thiamine (Vitamin B1). A severe and chronic form is known as beriberi. The two main types in adults are wet beriberi and dry beriberi. Wet beriberi affects the cardiovascular system, r ...
), especially in animals with simple stomachs.
Ruminant
Ruminants (suborder Ruminantia) are ungulate, hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by Enteric fermentation, fermenting it in a specialized stomach prior to digestion, principally ...
s are less vulnerable because they synthesize thiamine.
In animals
Ptaquiloside from bracken has been shown to be
carcinogen
A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...
ic in 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 in
buttermilk
Buttermilk is a fermented dairy drink. Traditionally, it was the liquid left behind after churning butter out of cultured cream. As most modern butter in western countries is not made with cultured cream but uncultured sweet cream, most mod ...
.
In pigs and horses, bracken poisoning induces vitamin B1 deficiency.
In insects
Hydrogen cyanide
Hydrogen cyanide, sometimes called prussic acid, is a chemical compound with the formula HCN and structure . It is a colorless, extremely poisonous, and flammable liquid that boils slightly above room temperature, at . HCN is produced on an ...
is released by the young fronds of bracken when eaten by mammals or insects. Two major insect
moulting
In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...
hormones, alpha
ecdysone
Ecdysone is a prohormone of the major insect molting hormone 20-hydroxyecdysone, which is secreted from the prothoracic glands. It is of steroidal structure. Insect molting hormones (ecdysone and its homologues) are generally called ecdysteroids. ...
and 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 new
insecticide
Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to b ...
s.
Archaeology
![Bleak hillside with bracken - geograph](https://upload.wikimedia.org/wikipedia/commons/6/66/Bleak_hillside_with_bracken_-_geograph.org.uk_-_1618991.jpg)
Many sites have archaeological remains dating from the
Neolithic
The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several parts ...
and
Bronze Age
The Bronze Age is a historic period, lasting approximately from 3300 BC to 1200 BC, characterized by the use of bronze, the presence of writing in some areas, and other early features of urban civilization. The Bronze Age is the second pri ...
s through to the
Industrial Revolution
The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
. The root systems of established bracken stands degrade archaeological sites by disrupting the
strata
In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ei ...
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.
Control
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
Natural England is a non-departmental public body in the United Kingdom sponsored by the Department for Environment, Food and Rural Affairs. It is responsible for ensuring that England's natural environment, including its land, flora and fauna, ...
and the
RSPB
The Royal Society for the Protection of Birds (RSPB) is a Charitable_organization#United_Kingdom, charitable organisation registered in Charity Commission for England and Wales, England and Wales and in Office of the Scottish Charity Regulator, ...
to control bracken either individually or in combinatio
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 botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...
. 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
Asulam is a herbicide invented by May & Baker Ltd , internally called M&B9057, that is used in horticulture and agriculture to kill bracken
Bracken (''Pteridium'') is a genus of large, coarse ferns in the family Dennstaedtiaceae. Ferns (Pt ...
(also known as Asulox) is selective for ferns;
glyphosate
Glyphosate (IUPAC name: ''N''-(phosphonomethyl)glycine) is a broad-spectrum Herbicide, systemic herbicide and Crop desiccation, crop desiccant. It is an organophosphorus compound, specifically a phosphonate, which acts by inhibiting the plan ...
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
''Ophioglossum vulgatum'', commonly known as adder's-tongue, southern adders-tongue or adders-tongue fern, is a species of fern in the family ''Ophioglossaceae''.
The adder’s tongue fern is generally believed to have the largest number of chro ...
''), 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
Natural England is a non-departmental public body in the United Kingdom sponsored by the Department for Environment, Food and Rural Affairs. It is responsible for ensuring that England's natural environment, including its land, flora and fauna, ...
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.
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
Image:Adelaarsvaren planten Pteridium aquilinum.jpg, ''Pteridium aquilinum''
Image:Tylerfinvold023 bracken ferns.jpg, Fronds of bracken
See also
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List of plants poisonous to equines
Many plants are poisonous to equines; the species vary depending on location, climate, and grazing conditions. In many cases, entire genera are poisonous to equines and include many species spread over several continents. Plants can cause reactio ...
References
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Germplasm Resources Information Network: ''Pteridium aquilinum''Flora Europaea: ''Pteridium aquilinum''Flora of North America: ''Pteridium aquilinum''
External links
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ttp://naturalengland.communisis.com/NaturalEnglandShop/product.aspx?ProductID=30f3211f-bc91-4e19-9d74-77b49cc0ba29 Natural England — Bracken control, vegetation restoration and land managementRSPB: Bracken management in the uplandsby
Butterfly Conservation
Butterfly Conservation (BC) is a UK-wide nonprofit environmentalist organization and charity dedicated to conserving butterflies, moths, and the environment. The charity uses its research to provide advice on how to conserve and restore butterfly ...
Edibility of Bracken Identification and edible parts of bracken
{{Taxonbar, from=Q258034
Dennstaedtiaceae
Japanese vegetables
IARC Group 2B carcinogens