Acrostichum speciosum

mangrove fern


Acrostichum speciosum

(Feé) C.Presl 1825

pronounced: ak-roe-STICK-um speck-ee-OH-sum

(Pteridaceae — the maidenhair fern family)

common name: mangrove fern

Acrostichum is from the Greek ακρος (akros), outermost, and στιχος (stichos), a row; speciosum is from the Latin speciosus, showy, beautiful, handsome.

There is some doubt as to the authorship of this plant. Both IPNI and Tropicos ascribe it to Willdenow, but the Kew Plant List gives (Feé) C.Presl. The Plant List even quotes Tropicos as its source, but Tropicos gives (Feé) C.Presl. as a synonym.

The species is restricted to tropical and south-east Asia and northern Australia. In Australia it is found in the coastal strip of northern Western Australia and the Northern Territory, and down the east coast of Queensland, into northern NSW. It is found in mangroves, tidal flats, brackish swamps and on coastal strips. In mangroves, it is usually found in colonies or clumps on the landward margin in high intertidal zones where there is some freshwater input. It is the only fern to inhabit the floor of the mangrove forest. It has also been recorded as growing on the periphery of, or occasionally within, saltmarshes in Queensland. The clump photographed was by the West Point road, on the edge of the mangroves.

This is a perennial clumping terrestrial fern growing up to 1.5 m high, with rhizomatous, often buttress-like roots. The caudex is stout and erect, bearing polished dark brown scales, spreading on to the stipe bases. The dark or dull green fronds are 30 – 150 cm tall, but mostly less than a metre, the stipe to 50 cm long, 3 – 8 mm in diameter; once-pinnate, the pinnae are on stalks about 1 cm long, and are leathery in texture, narrowly oblong or lanceolate, 10 – 20 cm long and 2 – 3 cm wide, with entire margins and a pointed tip. The venation is reticulate without free vein endings

When fertile, the apical few pinnae are completely covered with rusty brown sporangia beneath, although sometimes only the apical half of the pinna has fertile spores. The spores are large, tetrahedral, clear to translucent, 1 – 1.5 mm wide, and buoyant.

The stems, after being roasted, were used as a food by the Aborigines.
In Vietnam the fern is the preferred fuel for domestic cooking, the young leaves are eaten in times of famine, and the crushed rhizome is used to treat wounds and boils. In Malaya and some of the Pacific islands the fronds are used for thatching.

There are usually plenty of insects to be found on and around the plant, and they attract birds such as scrub hens.

Information about medicinal qualities of plants, or about their use as medicines, is for interest only, and is not intended to be used as a guide for the treatment of medical conditions.

Photographed by the West Point road, 2014
Page last updated 4th December 2019