Gahnia aspera  (R.Br.) Spreng. 1825

pronounced: GARN-ee-uh ASS-per-uh

(Cyperaceae – the sedge family)

common names:  Saw-sedge, Sword Grass

Gahnia saw-sedge is named for Dr Henrik Gahn (1747-1816), Swedish student of Linnaeus; aspera is from the Latin asper, rough, harsh. The plant was originally described by Robert Brown in 1810 as Lampocarya aspera, and placed in its current genus by the German botanist Kurt Sprengel in 1825.

This sedge is a widespread plant in the drier parts of rainforest, open forest and woodland on Cape York Peninsula, north-east Queensland and southwards as far as south-eastern NSW. It also occurs in Malaysia, New Guinea and the Pacific islands. It is often found in disturbed areas in well-developed rainforest.

It grows from an underground rhizome as a strappy tussock about 15 – 65 cm or more  in height, and to 50–150 cm across, and has long grass-like erect to spreading leaves to about 80 cm long with sharp, saw-edged margins. The underside of the leaves is also sharp, and these, with the edges, can easily cut human skin. The creamy flowers grow in spikes from the centre of the plant (usually from October to January), and are followed by shiny red or red-brown nuts, that measure up to 6 mm in length and 4 mm in width, globose to broad-ovoid, more-or-less terete. These fruits are very hard, and cannot be crushed between the teeth. When mature, they are pendulous, hanging from the infructescence by a fine thread. The embryo is small, and located near the base of the seed. The endosperm comprises most of the seed.

The caterpillars of several Lepidoptera feed on the leaves, including;

• the Spotted Sedge-skipper Hesperilla ornata;

• the Swordgrass Brown Tisiphone abeona;

• the Dark Palm Dart Telicota ancilla;

• the Two-spotted Sedge-skipper Hesperilla malindeva and

• the Flame Sedge-skipper Hesperilla idothea.

The seeds were pounded by the aboriginal peoples to make a type of flour. The leaf bases are also edible.

Saw-sedge has potential as a garden plant, although it needs to be kept away from borders and paths because of the sharpness of the foliage. It is quite difficult to grow from seed, but easy to propagate by division, if you can avoid being savaged by the leaves. It prefers a moist situation to produce best foliage, and will grow in semi-shade or some sun. In the garden is serves as shelter for small birds. On Magnetic Island, this sedge is usually found near watercourses, and the plant pictured was near Gustav Creek in Nelly Bay.

Photograph taken at Nelly Bay 2010

Page last updated 6th December 2016

 

 

 

 

 

 

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