Pteridium aquilinum

Pteridium aquilinum (bracken, brake or common bracken), also known as eagle fern, and Eastern brakenfern, is a species of fern occurring in temperate and subtropical regions in both hemispheres. The extreme lightness of its spores has led to its global distribution. Common bracken was first described as Pteris aquilina by Carl Linnaeus, in Volume 2 of his Species Plantarum in 1753. The origin of the specific epithet derived from the Latin aquila 'eagle'. In the reprint of the Flora Suecica in 1755, Linnaeus explains that the name refers to the image of an eagle seen in the transverse section of the root. In spite of this, the opinion has been forwarded that the name pertains to the shape of the mature fronds appearing akin to an eagle's wing. However, medieval scholars, including Erasmus, thought the pattern of the fibres seen in a transverse section of the stipe resembled a double-headed eagle or oak tree. It was traditionally treated as the sole species in the genus Pteridium (brackens); authorities have split and recognised up to 11 species in the genus, however. It was placed in the genus Pteridium by Friedrich Adalbert Maximilian Kuhn in 1879. Common bracken is a herbaceous perennial plant, deciduous in winter. The large, roughly triangular fronds are produced singly, arising upwards from an underground rhizome, and grow to 0.3–1 m (1–3ft) tall; the main stem, or stipe, is up to 1 cm (0.4 in) diameter at the base. It dies back to ground level in autumn. Sporangia are formed in sori on the underside of the frond. In Ireland found in open woodland and sandy pastures. An adaptable plant, bracken readily colonises disturbed areas. It can even be aggressive in countries where it is native, such as England, where it has invaded heather (Calluna vulgaris (L.) Hull) stands on the North Yorkshire moors. Bracken is a widely eaten vegetable in Korea, Japan and parts of China.