Bracken (Pteridium aquilinum) is a conspicuous fern that forms large clonal colonies in a variety of habitats. The large, more or less triangular leaves develop from fiddleheads that develop widely spaced along the branches of an extensive subterranean rhizome that may reach nearly 400 m in length. The taxonomy of the genus remains controversial, but most botanists currently favor a classification involving five or more species. In this sense, Pteridium aquilinum is distributed widely in mostly the northern hemisphere, in both the New and Old Worlds.

Bracken produces a pharmacopeia of toxic compounds, including: thiaminase (which breaks down the amino acid thiamine and results in vitamin B deficiency), ecdysomes (hormones that stimulate uncontrolled early molting in insects), tannins (which bind to proteins and other compounds), and hydrogen cyanide, and also produces carcinogenic compounds. The combination of chemicals renders the plants toxic to most animals, both invertebrates and vertebrates, although some insect specialists ingest bracken tissue to become poisonous to their predators. Humans have long eaten the fiddleheads (emerging young leaves) of bracken, but over-ingestion of fresh or dried fronds has been linked to stomach and esophageal cancers.

Bracken is an aggressive colonizer of disturbed and other successional habitats and has been considered an invader of pastureland. It has been shown to be allelopathic (to produce compounds that inhibit the growth of other plant species) and can for dense monocultures. It is difficult to eradicate or control and, because it is toxic, renders such pasturage unfit for grazing. Pteridium aquilinum is considered a noxious weed, especially in portions of Great Britain and mainland Europe.

Curled bracken shoots first appear in May, and are vulnerable to late frosts at this time (5). This species reproduces by means of spores, which are released from the brown spore-cases on the undersides of the fronds (5). It can also spread by vegetative reproduction, from a subterranean creeping storage organ known as a rhizome (2). When cut in half, the rhizome is said to display a pattern reminiscent of an oak tree, or outspread eagle wings (which may account for the specific name, aquila, which means eagle). It was also believed that letters could be seen in the patterns inside a rhizome; these were thought to show the initials of a future spouse (5). This fern also became associated with invisibility, although the reason is not entirely clear. It has been suggested that the lack of flowers may have fuelled the association; the mysterious absence of flowers was once thought to be magical (6). This species has been put to a wide range of practical uses, as manure, mulch, tinder, and fuel; in 18th Century Scotland it was burned to obtain potash needed for glass and soap manufacture, and it was (and still is in some areas) used as a bedding for livestock (6). One of its main uses, however, was as a packaging material (6). As these applications have declined, bracken cutting has ceased in many areas, and the species has spread dramatically as a result (6). Although livestock tend to avoid bracken, as it is extremely toxic, in dry years when there is very little else to eat livestock may browse on bracken, often with fatal results (6).

Archaeologists excavating a ca. 30 m² stable associated with Hadrian’s Wall in England (Roman, ca. 100 AD) found more than 250,000 puparia of the stable fly (Stomoxys calcitrans). Subsequently it was discovered that most of the larvae had pupated prematurely, before reaching full developmental maturity. The most likely cause of this phenomenon is that bracken was a major component of the plant litter used to line the floors of such structures, a testament to the efficacy of the insecticidal ecdysomes in the bracken. For a fascinating narrative on this situation and other aspects of bracken toxicology, see Robbin Moran’s (2004) excellent book, A Natural History of Ferns.

Medium- to large-size fern with an extensive underground rhizome, forming large colonies of broad, 2- to 4- times divided leaves.

Pteridium aquilinum was well-known to botanists in pre-Linnaean times, and Linnaeus (1753) cited older European literature sources in his description of Pteris aquilina. Maximilian Kuhn (1879), who studied pteridophyte specimens made during the African expedition of Baron Carl Claus von der Decken, determined that Pteris aquilina was best transferred to Pteridium, which had been described as a genus without a list of constituent species by Scopoli (1760). Pteridium aquilinum is thus the type species of the genus Pteridium Gled. ex Scop.

See GBIF. It should be noted that misdetermined or incompletely determined specimens in this difficult genus may result in spurious distributional data.

Basionym: Pteris aquilina L., Species Plantarum 2: 1075.
Linnaeus, C. 1753. Species Plantarum : Exhibentes Plantas Rite Cognitas, Ad Genera Relatas, cum Differentiis Specificis, Nominibus Trivialibus, Synonymis Selectis, Locis Natalibus, Secundum Systema Sexuale Digestas, vol. 2. Impensis Laurentii Salvii, Stockholm.

Combination: Pteridium aquilinum (L.) Kuhn, Botanik von Ost-Afrika 3(3): 11. 1879
von der Decken, C. C. 1869–1879. Baron Carl Claus von der Decken’s Reisen in Ost-Afrika in den Jahren 1859 bis 1861, 4 vols in 6 pts. C. F. Winter, Leibzig. [vol. 3, in 3 parts (1869–1879), = Beiträge zur Botanik, by various contributors]

Pteris aquilina L.:
Ecuador (South America)

Pteridium aquilinum (L.) Kuhn:
China (Asia)
Venezuela (South America)
Bolivia (South America)

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Almost ubiquitous, bracken is extremely common throughout Britain, and its range has increased dramatically during the 20th century. It occurs around the world, with the exception of the Arctic and Antarctic regions (4).

In the New World, Pteridium aquilinum in the strict sense occurs nearly throughout the United States and southern Canada, with extensions northward to about 55° N Latitude. The species is distributed southward through the mountains of Mexico into Central America as far as Honduras. It is also present in the Caribbean Islands and one subspecies is endemic to Hawaii. In the Old World, P. aquilinum occurs nearly throughout Europe (north to near the Arctic Circle) and Africa (excluding the Saharan portion), is present on a number of islands, including Madagascar, Réunion, the Mascarenes, Mauritius, and Macaronesia. Its Asian distribution extends eastward across Russia and south through China and Indochina into Malaysia. Farther south in both the Old and New Worlds, other species of Pteridium replace P. aquilinum, but there is distributional overlap between P. aquilinum and the other taxa, mainly in Latin America and portions of Asia.

In accord with the most recent revision (R. M. Tryon 1941) of the genus, Pteridium is treated here as a single widespread species composed of two subspecies with 12 varieties. So treated, it is probably the most widespread species of all vascular plants, with the exception of a few annual weeds (F. H. Perring and B. G. Gardner 1976). The plants are generally aggressive, invading disturbed areas as weeds in pastures, cultivated fields, and roadsides. In Europe, it was harvested and burned to produce potash. Although croziers are eaten in many temperate cultures, bracken has been shown to contain thiaminase (and other compounds with mutagenic and carcinogenic properties). 

 Disagreement exists among taxonomists regarding the rank that should be accorded to the taxa treated herein as varieties. In a survey of the genus, C. N. Page (1976) noted uniform chromosome numbers and flavonoid compositions of the varieties. D. B. Lellinger (1985) separated the genus into at least two species based on morphology, recognizing as species the subspecies of R. M. Tryon (1941). J. T. Mickel and J. M. Beitel (1988) reported sympatric occurrence in Mexico of three taxa that maintained consistent characteristics and only rarely produced plants with combined characteristics. They suggested that these three taxa should be considered as species that occasionally hybridize. P. J. Brownsey (1989) reported that two different brackens in Australia formed sterile hybrids and should be treated as species. Modern systematic studies are needed to evaluate the status and rank of the four North American varieties. As treated below, Pteridium aquilinum var. pubescens , var. latiusculum , and var. pseudocaudatum are in subsp. aquilinum , and var. caudatum is in subsp. caudatum (Linnaeus) Bonaparte.

Petioles scattered along creeping stems, 0.3--3.5 m, shallowly to deeply grooved adaxially, base not strongly distinct from stem. Blades broadly deltate, papery to leathery, sparsely to densely hairy abaxially, rarely glabrous. Pinnae often opposite to subopposite [alternate]; proximal pinnae often prolonged basiscopically, each proximal pinna nearly equal to distal part of leaf in size and dissection (except in var. caudata ). Segments alternate, numerous.

Medium- to large-sized ferns with a usually extensive system of long-creeping, branched, subterranean, hairy rhizomes, often forming large clonal colonies. Leaves mostly 0.5–1.5 m long, rarely to 2.5 m long, glabrous or variously hairy, long-petiolate, the petioles grooved along the upper side. Leaf blades 2 to 3 times pinnately compound and lobed, broadly deltate to deltate-triangular, ovate-triangular, or nearly pentagonal, the ultimate lobes or segments rounded to pointed at the tip, with strongly recurved, often pale margins, these irregular and usually sparsely to densely fringed along the edge, acting as a pseudoindusium to cover the developing sporangia (a true, outward-oriented indusium absent or vestigial). Sporangia in a continuous band along the leaf margins, hidden by the pseudoindusium until maturity. Spores 64 per sporangium, brown, nearly spherical (slightly tetrahedral), with a 3-branched tetrad scar (trilete), 23–40 μm in diameter, the outer surface irregularly granular. Source documents: Tryon (1941), Tryon and Tryon (1982), Kramer (1990), Tryon and Lugardon (1991), Jacobs and Peck (1993), Mickel and Smith (2004).

Pteris aquilina Linnaeus, Sp. Pl. 2: 1075. 1753

Large clonal ferns with medium- to large-size fronds. Rhizomes deeply seated, very long-creeping, repeatedly branched (some branches more elongate and not producing leaves, others shorter and frondiferous), densely pubescent with pale to dark brown, multicellular hairs; stele complex, described as two, concentric, highly corrugated solenosteles. Leaves (fronds) produced singly and remotely at rhizome nodes, (30–)50–150(–250) cm long. Petioles (stipes) not sharply distinct basally from the rhizome, (10–)25–100 cm long, erect or ascending, shallowly to deeply grooved adaxially, glabrous, glabrescent or hairy, the trichomes usually a mixture of short white hairs and minute gland-tipped, reddish hairs (these mostly in the groove); vascular bundles several, forming a U-shaped, horseshoe-shaped, or Ω-shaped pattern in cross-section. Laminae (blades) 20–150(–200) × 15–100 cm, broadly deltate to deltate-triangular, ovate-triangular, or nearly pentagonal, 2-pinnate-pinnatifid to 3-pinnate-pinnatifid (proximally), the pinnae mostly opposite to subopposite; proximal pinnae often prolonged basiscopically, the rachis and costae shallowly to deeply grooved with confluent, grooves, lacking prickles, pubescent similar to the petiole; small glandular patches (nectaries) present at bases of proximal and sometimes also distal pinnae; pinnules short to elongate, unlobed or few- to many-lobed, the lobes triangular to narrowly oblong or oblong-linear, rounded to pointed at the tips, the margins strongly reflexed; tissue chartaceous to somewhat coriaceous, abaxially glabrous to more commonly variously hairy (sometimes only on the costae and veins), adaxially glabrous or very sparsely hairy, except sometimes near the margins; veins mostly 1-forked, the branches often confluent marginally into a commissural vein. Sori an uninterrupted submarginal band along the commissural vein; excurrent true indusium absent or vestigial, a very slight ridge; pseudoindusium strongly developed, consisting of the recurved pinnule margin, this often white or pale, erose and often sparsely to densely long-ciliate. Sporangia with well-developed, triseriate stalks, the vertical annulus usually with a well-developed stomium. Spores 64 per sporangium, trilete, tetrahedral-globose, 23–32 μm in diameter, brown; perispore irregularly granular; exospore thin, undulate. Source documents: Tryon (1941), Tryon and Tryon (1982), Kramer (1990), Tryon and Lugardon (1991), Jacobs and Peck (1993), Mickel and Smith (2004).

This fern is found in moorland, hill pasture and a variety of other habitats with acidic soils. It particularly thrives on deep loams and sands, but is rare on alkaline soil; it has been found at heights of up to 585 m, but probably occurs higher than this in some areas (3).

Pteridium aquilinum is a terrestrial species that occurs in a wide variety of habitats, ranging from sand dunes to peatlands and open meadows to forests. It is especially aggressive in disturbed or successional habitats, including those prone to periodic disturbance by natural processes such as fires. Human-mediated perturbations such as grazing and timber removal tend to stimulate its growth and spread. It occurs from sea level to ca. 3300 m in soils derived from a wide variety of substrates and with various pH levels.

In Great Britain and/or Ireland:
Plant / associate
fruitbody of Amanita fulva is associated with Pteridium aquilinum

Plant / associate
fruitbody of Ampulloclitocybe clavipes is associated with Pteridium aquilinum

Foodplant / open feeder
larva of Aneugmenus coronatus grazes on frond of Pteridium aquilinum
Other: major host/prey

Plant / associate
Aneugmenus f is associated with Pteridium aquilinum
Other: major host/prey

Plant / associate
larva of Aneugmenus padi is associated with frond of Pteridium aquilinum
Other: major host/prey

Plant / associate
Aneugmenus temporalis is associated with Pteridium aquilinum
Other: major host/prey

Foodplant / saprobe
colony of Arthrinium dematiaceous anamorph of Arthrinium phaeospermum is saprobic on dead leaf of Pteridium aquilinum
Remarks: season: esp. 7-8

Foodplant / saprobe
solitary or few, epiphyllous, immersed then erumpent to superficial pycnidium of Ascochyta coelomycetous anamorph of Ascochyta pteridis is saprobic on dead petiolule of Pteridium aquilinum
Remarks: season: 7

Plant / epiphyte
fruitbody of Athelia pyriformis grows on dead frond of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Athelopsis lembospora is saprobic on decayed debris of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Basidiodendron cremeum is saprobic on dead, standing rachis of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Basidiodendron radians is saprobic on debris of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Basidiodendron spinosum is saprobic on decayed debris of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Boidinia furfuracea is saprobic on decayed debris of Pteridium aquilinum
Other: minor host/prey

Foodplant / saprobe
fruitbody of Botryobasidium danicum is saprobic on debris of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Botryobasidium pruinatum is saprobic on debris of Pteridium aquilinum

Foodplant / parasite
effuse colony of Botryosporium anamorph of Botryosporium pulchrum parasitises live Pteridium aquilinum
Remarks: season: 5-11

Foodplant / saprobe
linearly arranged, subepidermal then epidermis turns brown and opens by a slit conidioma of Camarographium coelomycetous anamorph of Camarographium stephensii is saprobic on dead petiole of Pteridium aquilinum
Remarks: season: 5-7

Foodplant / feeds on
basidiome of Ceratobasidium anceps feeds on live frond of Pteridium aquilinum

Foodplant / saprobe
effuse colony of Chalara dematiaceous anamorph of Chalara fungorum is saprobic on dead Pteridium aquilinum

Foodplant / saprobe
effuse colony of Chalara dematiaceous anamorph of Chalara parvispora is saprobic on dead frond of Pteridium aquilinum
Remarks: season: 5

Foodplant / saprobe
effused Chalara dematiaceous anamorph of Chalara pteridina is saprobic on dead petiole of Pteridium aquilinum
Remarks: season: 4-11

Foodplant / saprobe
erumpent pycnidium of Coniothyrium coelomycetous anamorph of Coniothyrium pteridis is saprobic on dead pinna of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Crepidotus luteolus is saprobic on dead stem of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Cristinia helvetica is saprobic on decayed debris of Pteridium aquilinum

Foodplant / saprobe
short-stalked apothecium of Crocicreas cyathoideum var. cyathoideum is saprobic on dead stem of Pteridium aquilinum
Remarks: season: 3-10

Foodplant / saprobe
short-stalked apothecium of Crocicreas cyathoideum var. pteridicola is saprobic on dead stem of Pteridium aquilinum
Remarks: season: 4-7

Plant / resting place / on
adult of Cryptocephalus bipunctatus may be found on near ant nest Pteridium aquilinum
Remarks: season: 4-late 8

Foodplant / saprobe
conidioma of Cryptomycella coelomycetous anamorph of Cryptomycina pteridis is saprobic on dead frond of Pteridium aquilinum

Foodplant / pathogen
Dactylium dendroides ssp. leptosporum infects and damages diseased frond of Pteridium aquilinum

Foodplant / gall
larva of Dasineura filicina causes gall of frond of Pteridium aquilinum

Foodplant / saprobe
erumpent conidioma of Phomopsis coelomycetous anamorph of Diaporthopsis pantherina is saprobic on dead petiole of Pteridium aquilinum
Remarks: season: 2+

Foodplant / saprobe
epiphyllous, densely gregarious pseudothecium of Didymella lophospora is saprobic on dead frond of Pteridium aquilinum
Remarks: season: 7

Foodplant / saprobe
immersed, raising the epidermis pseudothecium of Didymella prominula is saprobic on dead stem of Pteridium aquilinum
Remarks: season: 6

Foodplant / saprobe
fruitbody of Endoperplexa enodulosa is saprobic on decayed debris of Pteridium aquilinum

Foodplant / saprobe
Exochalara anamorph of Exochalara longissima is saprobic on Pteridium aquilinum

Foodplant / debris feeder
larva of Fannia monilis feeds on rotten Pteridium aquilinum

Foodplant / saprobe
fruitbody of Galerina ampullaceocystis is saprobic on debris of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Galerina cinctula is saprobic on debris of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Galerina marginata is saprobic on debris of Pteridium aquilinum

Plant / associate
fruitbody of Geastrum triplex is associated with Pteridium aquilinum
Other: minor host/prey

Foodplant / saprobe
fruitbody of Hemimycena delectabilis is saprobic on decayed debris of Pteridium aquilinum

Plant / associate
fruitbody of Hygrocybe laeta var. laeta is associated with live Pteridium aquilinum

Foodplant / saprobe
fruitbody of Hyphodontia detritica is saprobic on dead, decayed frond of Pteridium aquilinum
Other: minor host/prey

Foodplant / saprobe
fruitbody of Hyphodontia griseliniae is saprobic on dead, decayed debris of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Hypochnicium geogenium is saprobic on dead, fallen, decayed debris of Pteridium aquilinum
Other: minor host/prey

Foodplant / saprobe
apothecium of Lachnum pteridialis is saprobic on dead frond of Pteridium aquilinum
Remarks: season: 10

Foodplant / saprobe
apothecium of Lachnum pteridis is saprobic on dead stem of Pteridium aquilinum
Remarks: season: 8-5

Foodplant / saprobe
long stalked apothecium of Lachnum virgineum is saprobic on dead frond of Pteridium aquilinum
Remarks: season: 2-10

Plant / associate
fruitbody of Lactarius camphoratus is associated with Pteridium aquilinum

Foodplant / saprobe
Pycnothyrium anamorph of Leptopeltis litigiosa is saprobic on dead petiole of Pteridium aquilinum
Remarks: season: 6-9

Foodplant / saprobe
subcuticular, usually confluent thyriothecium of Leptopeltis pteridis is saprobic on dead frond (vein) of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Leptosporomyces galzinii is saprobic on dead, decayed debris of Pteridium aquilinum
Other: unusual host/prey

Foodplant / saprobe
fruitbody of Leucoagaricus georginae is saprobic on dead, decayed debris of Pteridium aquilinum
Other: unusual host/prey

Foodplant / saprobe
thyriothecium of Lichenopeltella nigroannulata is saprobic on dead frond of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Lindtneria trachyspora is saprobic on dead stem of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Litschauerella clematidis is saprobic on dead stem of Pteridium aquilinum
Other: unusual host/prey

Foodplant / saprobe
fruitbody of Luellia cystidiata is saprobic on dead, decayed debris of Pteridium aquilinum
Other: unusual host/prey

Foodplant / saprobe
fruitbody of Luellia recondita is saprobic on dead stem of Pteridium aquilinum
Other: major host/prey

Foodplant / saprobe
fruitbody of Marasmiellus vaillantii is saprobic on dead stem of Pteridium aquilinum

Foodplant / pathogen
fruitbody of Marasmius undatus infects and damages dying rhizome of Pteridium aquilinum
Other: sole host/prey

Foodplant / saprobe
immersed, exposed by irregualr splitting of epidermis apothecium of Mellitiosporium pteridinum is saprobic on dead stem of Pteridium aquilinum
Remarks: season: 3-4

Plant / associate
fruitbody of Micromphale impudicum is associated with Pteridium aquilinum

Foodplant / saprobe
apothecium of Micropodia pteridina is saprobic on dead stem of Pteridium aquilinum
Remarks: season: 3-9

Foodplant / saprobe
hypophyllous, short-stalked apothecium of Microscypha grisella is saprobic on damp, dead frond of Pteridium aquilinum
Remarks: season: 5-8

Foodplant / saprobe
apothecium of Mollisia pteridis sensu Gillet is saprobic on locally blackened, dead, standing stem of Pteridium aquilinum
Remarks: season: 6-7

Foodplant / sap sucker
adult of Monalocoris filicis sucks sap of sporangia of Pteridium aquilinum
Other: major host/prey

Foodplant / gall
larva of Monochroa cytisella causes gall of stem, side-shoot of Pteridium aquilinum

Foodplant / saprobe
ascocarp of Monographos fuckelii is saprobic on dead petiole of Pteridium aquilinum
Remarks: season: 7-8

Foodplant / saprobe
fruitbody of Mycena amicta is saprobic on dead, fallen, decayed litter of Pteridium aquilinum
Other: unusual host/prey

Foodplant / saprobe
fruitbody of Mycena arcangeliana is saprobic on dead, decayed stem of Pteridium aquilinum
Other: unusual host/prey

Foodplant / saprobe
fruitbody of Mycena clavularis is saprobic on dead, decaying debris of Pteridium aquilinum
Other: unusual host/prey

Foodplant / saprobe
fruitbody of Mycena epipterygia is saprobic on dead, decayed debris of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Mycena pterigena is saprobic on dead, decayed debris of Pteridium aquilinum

Foodplant / saprobe
toadstool of Mycena vulgaris is saprobic on dead, fallen, decaying debris of Pteridium aquilinum
Other: minor host/prey

Foodplant / parasite
Mycosphaerella aspidii parasitises Pteridium aquilinum

Foodplant / saprobe
epiphyllous, often grouped, immersed pseudothecium of Mycosphaerella pteridis is saprobic on dead frond of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Oliveonia pauxilla is saprobic on dead, decayed debris of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Phanerochaete martelliana is saprobic on dead stem of Pteridium aquilinum

Foodplant / saprobe
hypophyllous apothecium of Phialina flaveola is saprobic on damp, dead frond of Pteridium aquilinum
Remarks: season: 6-7

Foodplant / saprobe
fruitbody of Phlebiella christiansenii is saprobic on debris of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Phlebiella fibrillosa is saprobic on dead, decayed debris of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Phlebiella filicina is saprobic on dead, decayed debris of Pteridium aquilinum
Other: major host/prey

Foodplant / saprobe
deeply immersed perithecium of Phomatospora endopteris is saprobic on dead frond of Pteridium aquilinum

Foodplant / saprobe
gregarious, lirelliform pycnidium of Phomopsis coelomycetous anamorph of Phomopsis aquilina is saprobic on dead rhachis of Pteridium aquilinum
Remarks: season: 8-9

Plant / resting place / on
puparium of Phytoliriomyza hilarella may be found on frond of Pteridium aquilinum

Foodplant / feeds on
Procas granulicollis feeds on Pteridium aquilinum
Remarks: Other: uncertain

Foodplant / saprobe
short-stalked apothecium of Psilachnum chrysostigmum is saprobic on dead frond of Pteridium aquilinum
Remarks: season: 10-5

Foodplant / saprobe
sessile apothecium of Psilachnum pteridigenum is saprobic on dead frond of Pteridium aquilinum
Remarks: season: 5-9

Plant / associate
fruitbody of Ramariopsis kunzei is associated with debris of Pteridium aquilinum

Foodplant / saprobe
subepidermal, often confluent stroma of Rhopographus filicinus is saprobic on dead petiole of Pteridium aquilinum
Remarks: season: 2-6

Foodplant / saprobe
subepidermal, splitting the epidermis stroma of Scirrhia aspidiorum is saprobic on dead petiole of Pteridium aquilinum
Remarks: season: 5-7

Plant / associate
fruitbody of Scleroderma cepa is associated with Pteridium aquilinum
Other: unusual host/prey

Foodplant / saprobe
fruitbody of Scotomyces subviolaceus is saprobic on dead, decayed debris of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Sistotrema oblongisporum is saprobic on dead, decayed debris of Pteridium aquilinum

Foodplant / saprobe
Sphaerothyrium coelomycetous anamorph of Sphaerothyrium filicinium is saprobic on dead Pteridium aquilinum

Foodplant / saprobe
effuse colony of Stachylidium dematiaceous anamorph of Stachylidium bicolor is saprobic on dead stem of Pteridium aquilinum

Foodplant / open feeder
larva of Strombocerus delicatulus grazes on frond of Pteridium aquilinum
Other: major host/prey

Foodplant / open feeder
larva of Strongylogaster filicis grazes on frond of Pteridium aquilinum
Other: major host/prey

Foodplant / open feeder
larva of Strongylogaster lineata grazes on frond of Pteridium aquilinum
Other: major host/prey

Foodplant / open feeder
larva of Strongylogaster macula grazes on frond of Pteridium aquilinum
Other: major host/prey

Foodplant / open feeder
larva of Strongylogaster xanthocera grazes on frond of Pteridium aquilinum
Other: sole host/prey

Foodplant / internal feeder
larva of Syagrius intrudens feeds within rootstock of Pteridium aquilinum

Foodplant / open feeder
nocturnal larva of Tenthredo colon grazes on frond of Pteridium aquilinum

Foodplant / open feeder
nocturnal larva of Tenthredo ferruginea grazes on frond of Pteridium aquilinum

Foodplant / open feeder
nocturnal larva of Tenthredo livida grazes on frond of Pteridium aquilinum

Plant / associate
fruitbody of Tephrocybe confusa is associated with Pteridium aquilinum

Plant / resting place / on
fruitbody of Tomentella radiosa may be found on dead, decayed debris of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Trechispora stellulata is saprobic on dead, decayed stem of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Tricholomopsis rutilans is saprobic on dead, decayed debris of Pteridium aquilinum
Other: unusual host/prey

Foodplant / saprobe
Tubulicrinis regificus is saprobic on dead stem of Pteridium aquilinum

Foodplant / saprobe
basidiome of Tulasnella brinkmannii is saprobic on dead stem of Pteridium aquilinum

Foodplant / saprobe
fruitbody of Typhula quisquiliaris is saprobic on dead, decayed stem of Pteridium aquilinum
Other: major host/prey

Pteridium aquilinum is especially aggressive in disturbed or successional habitats, including those prone to periodic disturbance by natural processes such as fires.

Pteridium aquilinum is a genetically diploid, sexual, homosporous fern producing haploid spores that are dispersed by air and gravity. The spores germinate to produce small, potentially bisexual gametophytes. In spite of the potential for intragametophytic self-fertilization, genetic data suggest that bracken sporophytes in nature mainly are the result of outcrossing between gametophytes (Wolf et al., 1988, 1991). Klekowski (1972) presented data showing that this outcrossing was not due to the presence of a genetic incompatibility system, but that genetic load (the presence of deleterious alleles in natural populations that minimize the number of successful self-fertilizations) might play a role in enforcing outcrossing.

In vitro studies also have shown that bracken gametophytes have an antheridiogen system (Döpp, 1950); that is, the first gametophytes developing at a site become functionally female and produce hormonal substances (antheridiogens) that cause subsequently developing gametophytes nearby to become functionally male. In fact Döpp’s initial report on the existence of antheridiogens involved the study of cultured gametophytes of Pteridium aquilinum, and the species is still used a standard for assaying the production of antheridiogen A in ferns.

The studies of Wolf et al. (1991) on plants in Britain also have shown that the high dispersability of bracken spores leads to high rates of gene flow and consequently potentially very large metapopulations.
In nature, many bracken plants rarely produce sporangia. In such populations, sexual reproduction does not occur regularly. Vegetative reproduction is thus very important in bracken and is accomplished by fragmentation of the long-creeping, branched rhizomes. Some rhizome branches are leafless and elongate extensively as a mechanism to increase the overall size and spread of the clone. Bracken is one of the largest organisms in the world. Sheffield et al. (1989b) used isozyme data to document a single clone of Pteridium aquilinum in Great Britain whose rhizome apparently covered an area 390 m in length.

Apospory on aberrant fronds in nature was demonstrated by Farlow (1889) and confirmed by Whittier (1966a). Whittier (1966b) also demonstrated in vitro that normal haploid gametophytes and diploid gametophytes resulting from apospory could be induced to become apogamous.

The mostly northern hemisphere distribution of Pteridium aquilinum sensu stricto vs. the mostly southern hemisphere distribution of the remaining diploid species in the genus is suggestive of a Laurasian/Gondwanan split, however, there is no fossil evidence to directly confirm the development this biogeographic pattern. Currently, there is a large area of geographic overlap between the two groups in Latin America and portions of southern Asia. Rymer (1973) reviewed the fossil history of Pteridium. The oldest macrofossils attributed to the genus date to the Oligocene of Hungary, and unequivocal leaf compressions of Pteridium have been recorded from the late Miocene of England and late Pliocene of New Zealand (Oliver, 1928). Rymer reviewed the Quaternary history of Pteridium in Great Britain in somewhat more detail, noting that its distribution waxed and waned during successive glacial and interglacial stages, and that generally the current distribution of P. aquilinum is a relatively recent phenomenon affected greatly by prehistoric and historic human-mediated perturbations such as clearing of forests and introduction of livestock.

Although the taxonomy of the genus Pteridium is still controversial, four or five species are often accepted in modern accounts, including: P. aquilinum (L.) Kuhn sensu stricto, P. arachnoideum (Kaulf.) Maxon, P. caudatum (L.) Maxon, P. esculentum (G. Forst.) Cockayne, and P. semihastatum (Wall. ex J. Agardh) S.B. Andrews (P. yarrabense (Domin) N.A Wakef.) (Thomson, 2004).

The list of epithets that have been applied as infraspecific taxa within P. aquilinum when the genus was still considered monospecific includes nearly 20 names. A number of these are now applied to segregate species within the genus and the taxonomic status of most others still has not been fully resolved.

The genus Pteridium is a member of the homosporous fern family Dennstaedtiaceae. Generic relationships within the family still are not fully understood, but the genus is morphologically quite distinct. The taxonomy and classification within Pteridium continues to be controversial. Traditionally and as monographed by Tryon (1941), the genus was thought to comprise a single, highly variable and nearly cosmopolitan species, P. aquilinum, which could be divided into two subspecies, with a complex series of eight and four varieties respectively. However, over time, some of the morphological variants became elevated to separate species status, with the result that more than a dozen species epithets have been published within the genus. Long-term research on the systematics and phylogeny of Pteridium, mainly by John Thomson (National Herbarium of New South Wales) and his collaborators (Thomson, 2004) has resulted in the recognition of four or five species: a New and Old World northern hemisphere diploid (P. aquilinum sensu stricto), a pair of closely related New and Old World mostly southern hemisphere diploids (P. arachnoideum, P. esculentum), an uncommon neotropical tetraploid (P. caudatum), and a Malaysian/Australian tetraploid (P. semihastatum, aka. P. yarrabense). Within P. aquilinum sensu stricto, infraspecific classification also continues to be controversial, with ten or more geographically and morphologically defined subspecies possibly recognized.

Cyanide protects from herbivores: brackenfern
 

Bracken protects its leaves from being eaten by filling them with cyanide.

   
  "Bracken, that most widespread of ferns in Britain, fills its young tender leaves with cyanide. That deters most insects...By the time the leaves are mature and so tough that they seem likely to be of interest only to larger grazers such as rabbits and deer, they have manufactured a cocktail of toxins so powerful that they can cause blindness and cancer in mammals." (Attenborough 1995:70)
  Learn more about this functional adaptation.

Much has been written on the biochemistry of bracken because of its toxicity (see under Toxicity).  As noted under Life History, Pteridium aquilinum was the first species in which the production of antheridiogens (hormones that cause gametophytes to become exclusively male, thus facilitating cross-fertilization) was detailed.  Gametophytes of the species also have been model systems for the in vitro study of gametophyte growth and development, as well as the induction of apogamy and apospory (e.g., Whittier, 1966b, c; Sobota and Partanan, 1967; Raghavan, 1969, 1970

The genus Pteridium has been nearly uniformly reported as having n=52 or 2n=104 from numerous reports covering several of the described taxa within P. aquilinum (for a summary, see Löve et al., 1977). This ploidy generally is regarded as the current diploid in the genus. However, a few exceptions exist. Löve and Kjellqvist (1972) reported a count of n=26 from a plant that they referred to P. herediae. This count, which was published without documenting photos or illustrations, was later refuted as based on an aberrant cell by Sheffield et al. (1986, 1989a). Additionally, an apparent tetraploid count of 2n=208 was reported by Jarrett et al. (1983) from the Galapagos and a second tetraploid from Malaysia and Australia was inferred by Thomson (2000a, b) based on morphometric and DNA fingerprinting data (but no cytological data). However, these unusual New and Old World polyploids are best treated as allopolyploid species separate from P. aquilinum sensu stricto (Thomson, 2004). Sheffield et al. (1993) also reported an unusual, partially fertile, triploid clone from England with 2n=156, whose taxonomic affinities await further research.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 9
Species: 11
Species With Barcodes: 1

A number of systematic and phylogenetic studies have been published on the genus involving molecular and other genetic data, but thus far there has not been a comprehensive account. Papers involving Pteridium aquilinum: cpDNA restriction site analysis (Jubrael et al., 1986, 1990; Tan and Thomson, 1990b; Thomson et al., 1995); arbitrarily-primed PCR fingerprinting of nuclear genome (Thomson 2000a, b; Thomson and Alonso-Amelot, 2002; Thomson et al., 2005); ISSR analysis (Thomson et al., 2005); isozyme analysis (Wolf et al., 1988, 1991; Sheffield et al., 1989a, b, 1993, 1995; Rumsey et al., 1991; Bridges et al., 1998; Speer et al., 1999); genome size (Tan and Thomson, 1990a); chloroplast sequence data (Wolf et al., 1995; Speer, 2000); mitochondrial sequence data (Wolf et al., 1995); nuclear sequence data (Thomson et al., 1995, 2000; Wolf et al., 1995).

See under Reproduction and Life History for additional references on genetics.

The species Pteridium aquilinum is considered globally Secure. Conversely, it is considered a noxious weed (officially or unofficially) in portions or North America, Europe, New Zealand, and Australia.

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Very widespread and common (3).

Not threatened at present.

Control of bracken is very difficult. Mechanical control of aboveground portions of the plants is ineffective, because of the deep-seated perennial rhizome, as is application of controlled burns. Plowing is somewhat effective when crop fields have been infested, but is not feasible in most natural habitats. Under natural conditions, bracken frond density decreases with increasing shade as forest canopies develop closure, but this is a lengthy process and sometimes at odds with other management objectives for given parcels of land.

On a small scale, bracken ferns can be controlled by foliar application of herbicides such as glyphosate and asulam, with repeated application to resprouting fronds necessary and the use of a surfactant to facilitate uptake of the herbicide through the waxy cuticle increasing the chances of success. At larger geographic scales, herbicides have been applied by aircraft, but this process has the potential to impact adjacent nontarget plant species.

Biological controls have thus-far not been implemented successfully to control stands of Pteridium aquilinum in nature. However, searches for potential organisms with which to develop a biocontrol program have been going on for years, principally in Great Britain, mainly involving potential fungal and insect pathogens. Source documents: Gaskin et al. (1986), Sharma and Kirkwood (1995), Womack et al. (1995); Petrov and Marrs (2000), Robinson (2000), Robinson and Page (2000), Fowler (2002).

Pteridium is not recommended for gardens, as it is too aggressive, the deep-seated, creeping rhizomes are difficult to control, and the plants release allelopathic compounds into the soil that inhibit the growth of other plants. Occasionally, it is planted in places where a large space needs to be filled.

No conservation action is required for this very common species.

Occasionally, in gardens around the world that have sufficient space to allow for a colony.

Rymer (1976) reviewed the ethnobotany of Pteridium aquilinum. Historically, dried fronds of bracken were used to stuff mattresses, as other bedding, and as litter to cover floors, because of their insecticidal properties. Whole plants were used in thatch for houses and fronds were used to shade and cover other items. The fronds also decay quickly when mixed with urine, dung, or other organic material; thus the species has been used in composting. Bracken was burned historically to produce potash, which is used in the manufacture of soap and glass, as well as in dyeing, bleaching, and wool scouring. It also was a fuel for cookfires and lime kilns. Minor uses included as a tanning agent for leather and as a substitute or adulterant for hops in beer brewing.

The emerging young fiddleheads are collected for human consumption in most regions where the fern is abundant, especially in portions of Asia. This practice is to be discouraged, however, because of the strong link between heavy ingestion of fresh or dried bracken leaves and the incidence of stomach cancer (see also under toxicity).

According to Rymer (1976), bracken had a number of medicinal uses in Europe. As with many ferns, the rhizome was used as an anthelmintic. The rhizomes and leaves also were used in various tonics and even as an aphrodesiac.

Moerman (1998 and http://herb.umd.umich.edu) noted a number of medicinal uses among North American Indian tribes, including: the use of rhizomes as an antiemetic, antihemorrhagic, analgesic, tonic, and for skin problems; an infusion of fronds used as a gynecological aid, antirheumatic, and for liver, urinary, and venereal problems; and a poultice of leaves for skin sores. Plants also were used in basketry and sleeping mats, to cover produce and fish, and cooking aid.

Pteridium aquilinum is highly palatable, but toxic, to animals, both invertebrates and vertebrates. Several modes of action have been studied:

The fronds produce a large number of ecdysomes, which are hormones that cause uncontrolled molting in insect larvae and thus disrupt normal maturation processes.

The fronds, are cyanogenic. They contain a substance known as prunasin that is converted into the poison, hydrogen cyanide, in response to tissue damage (such as from insect predation).

The plants, particularly the rhizomes and young fronds, produce type I thiaminase, an enzyme that breaks down thiamine and thus causes vitamin B deficiency. The effects are cumulative over time and even hay contaminated with bracken can produce symptoms. The name bracken staggers has been applied to this problem in horses, but a variety of neurological symptoms occur and also anorexia, hemorrhaging, conjunctivitis, fever, muscular tremors and spasms, accelerated heartbeat, and seizures. Some of the symptoms are thought to represent more than one interacting causal agent. Mortality can be high.

The plants are rich in tannins, which bind to proteins, enzymes, and other cellular products, doing all sorts of harm in the bodies of organisms that ingest the tissues of bracken. Cooking tends to break down tannins.
The plants are carcinogenic, containing a substance known as ptaquiloside, as well as other norsesquiterpene glucosides. Regions in which humans ingest large quantities of bracken have long been known to have elevated rates of stomach and esophageal cancers, and various gastrointestinal and urinary cancers also have been observed in livestock. Related symptoms in some animals include retinal degeneration (bright blindness of sheep) and acute hemorrhagic disease (tied to degeneration of the bone marrow). Laboratory experiments on animals confirmed the link between Pteridium and these symptoms. When bracken is eaten by cattle, ptaquiloside apparently also can be transmitted through the milk, potentially leading to stomach and esophageal cancers. Even the spores are carcinogenic.

Bracken also can contribute secondarily to human health hazards. Areas with dense stands of bracken can develop a thick layer of decaying thatch from old fronds and a humid microhabitat develops under the canopy of living fronds. Such a habitat apparently promotes higher densities of ticks that are carriers of Lyme Disease.

Additionally, bracken has been shown to be allelopathic (producing compounds that inhibit the germination/growth of other plants), although the results of laboratory studies to demonstrate this have varied. Source documents: Hodge (1973), I. A. Evans (1976, 1986), W. C. Evans (1976, 1986), Gliessman (1976), Hannam (1986), Hudson (1986), Ferguson and Boyd (1988), Hirono (1990), Villalobos-Salazar et al. (1990, 1995), Brown (10995), Hopkins (1995), Ouden (1995), Potter and Pitman (1995), Alonso-Amelot et al. (2000), Simán et al. (2000), Smith et al. (2000), Burrows and Tyrl (2001), Moran (2004).

• Dr. John A. Thomson
• Dr. Elizabeth A. Sheffield
• Dr. Paul G. Wolf

• BioImages (extensive images from Britain plus table of associated invertebrates)
• USDA Plants Profile: Pteridium aquilinum (extensive summary information and several images from the U.S.A.)
• International Bracken Group
• Native American ethnobotany