Angiopteris evecta

A. evecta growing on the Lamb Range, Queensland, Australia

A. evecta near Cape Tribulation, Australia

Angiopteris evecta is a self-supporting evergreen perennial fern with very large bipinnate fronds. The massive trunk-like rhizome grows vertically up to 1.2 m (3.9 ft) high by 1 m (3.3 ft) wide. The arching, glossy green fronds, which emanate from the top of the trunk, may reach up to 2.5 m (8.2 ft) wide and 9 m (30 ft) long, with the fleshy green petiole (leaf stem) making up 2 m (6.6 ft) of that length.[5][6][10][11] They are said to be the longest fern fronds in the world.[12][13][14] Despite their size they have no strengthening tissues, instead they are supported entirely by the turgor pressure of the sap.[15] The rachises, pinnae and pinnules are all pulvinate. Sporangia are borne on the underside of the pinnules, very close to the margin, in clusters of 5 to 8 opposite pairs.[10][15] On either side of the petiole where it arises from the trunk there are flat, rounded, leathery, ear-shaped stipules, known as "auricles",[16] which can measure up to 10 to 15 cm (3.9 to 5.9 in). Overall dimensions of this fern can be up to 7 m (23 ft) high by 16 m (52 ft) wide.[4][5][10][11][17][18]

Underside of a pinnule of A. evecta, showing sporangia

Angiopteris evecta is the type species of the genus Angiopteris.[19] It was originally named Polypodium evectum and described by Georg Forster in 1786,[20] but was reclassified in 1796 by Georg Franz Hoffmann.[21] There are many synonyms (see Synonyms section below) which are considered by some authorities to potentially be distinct species, calling for a more thorough taxonomic investigation.[4][6][22]

The genus name comes from the Ancient Greek aggeion, a vessel, and pteris, a fern. The species epithet derives from the Latin adjective evectus meaning swollen or inflated.[5]

Rachis of a frond of A. evecta, showing pulvini at the bases of side branches

Fossil records in Paleozoic rocks have been found which are very similar to Angiopteris evecta, indicating that the species has been in existence for around 300 million years.[12][13][14][18][23] The geographically isolated communities seen today point to favourable climatic conditions being more widespread in the past.[5]

Angiopteris evecta is native to southeast Asia, from Singapore through Indonesia, Papua New Guinea and Australia to Melanesia, Micronesia and Polynesia. It has been introduced to most of the rest of tropical Asia, as well as Madagascar and parts of the tropical Americas.[3][6][5][9]

The species grows in very rich soils, often of volcanic origin[4][5] and prefers a very warm wet climate. It is most commonly found as an understorey plant in well developed rainforest, especially along creek banks in deep sheltered gullies where there is good drainage but also a plentiful supply of fresh water.[5][8][17] The preferred annual mean temperature range is 19–27 °C (66–81 °F) and annual precipitation between 1,000–5,447 mm (39.4–214.4 in). It may grow at altitudes from sea level to 1,500 m (4,900 ft)[4][6][11]

The starchy rhizomes are eaten after long processing to remove toxins,[5] used to perfume coconut oil, [6][11] to flavour rice and to produce an intoxicating drink.[5] The 1889 book The Useful Native Plants of Australia records Indigenous Australians ate the pith of this fern.[24]

The conservation status of Angiopteris evecta varies from place to place. For example in Australia's Northern Territory it is listed as vulnerable, with only one small population in north eastern Arnhem Land;[13][25] in New South Wales, where suitable habitat is restricted to a small area in the north east corner of the state and only a single, non-reproductive specimen is known,[5] it is listed as endangered.[17][25] However in Queensland, which sits in between the previous two and where there is an abundance of suitable habitat, it is listed as least concern.[17][25][26]

When introduced to an area with a suitable climate, Angiopteris evecta can establish dense stands that inhibit local species. It is listed as invasive in Costa Rica, Cuba, Jamaica and Hawaii, where in each case it has escaped from plantings in botanic gardens. It has also been introduced to many tropical countries and has repeatedly escaped from cultivation.[6]

Plants of the World Online lists 74 synonyms for Angiopteris evecta:[3]

Map of observations of Angiopteris evecta at the Australasian Virtual Herbarium