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 bräkencode: swe promoted to code: sv 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
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 2.5 m (8 ft) long or longer with support, but typically are in the range of 0.6–2 m (2–6+1⁄2 ft) 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 As of August 2026, Plants of the World Online accepted 20 species:
Distribution and habitat
Pteridium aquilinum (bracken or common bracken) is the most common species of this genus with a cosmopolitan distribution (occurring in suitable habitats in temperate and subtropical regions throughout much of the world). It is a prolific and abundant plant in the moorlands of Ireland, where it is limited to altitudes of below 600 metres (2,000 ft). 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.
As of the mid-1990s, 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,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 citing a Bracken Advisory Commission member and professor of sustainable land use. 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. 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". (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.) Bracken is a characteristic moorland plant in Ireland, which over the last decades has increasingly out-competed characteristic ground-cover plants such as moor grasses, cowberry, bilberry, and heathers. It now covers a considerable part of upland moorland. It causes problems in its invading pasturelands.
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. 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. Bracken can harbour high levels of sheep ticks, which can pass on Lyme disease. Grazing provided some control by stock trampling, but this has almost ceased since the 2001 foot-and-mouth disease outbreak reduced commercial livestock production. 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. Bracken is known to form large fern prairies (sometimes known as fern savannahs or the Fernland). Some of these are natural but others can be formed via fires created by humans. Brackens are also key parts of other types of savannah such as Pine savannah and Pineyards.
Ecology
Evolutionarily, bracken may be considered one of the most successful ferns. It is considered highly invasive, and can survive in acid soils.
Fungal associations
Woodland fungi such as Mycena epipterygia can be found growing under the bracken canopy. Both Camarographium stephensii and Typhula quisquiliaris grow primarily from dead bracken stems.
Other plant associations
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