Gahnia grandis

Appearance

''Gahnia grandis'' is a perennial tussock-forming sedge growing to 1–3 × 2–3m tall. The flowering stems are stout, often sprawling before becoming erect. The sharp-edged leaves are flat, brown-sheathed, and channelling to a 2.5m long, narrow, spiral stem. The inflorescences emerge from a long, tangled stem with weeping leaves. The stems are stout, 1–3 m high and c. 2–10 mm in diameter, often sprawling for 1–2 m from their base. It is widespread throughout Tasmania.

Flowers may be drooping, with spikes 50–100 cm long. They are often one-sided, with bracts much shorter on the lower than on the upper side. The flower-heads are panicle-like in shape. The flowers are in spikelets. Each spikelet is two-flowered, the upper flower being bisexual and the lower flower sterile or male. The lowest glumes, which number 8-12, are much shorter than the upper glumes, and are irregularly toothed at the brown to dark grey-brown erose . The erose is slightly rough to the touch. The apex of the plant's upper glumes is pointed to bluntly-rounded. The cream-coloured flowers possess 4-5 stamens with 2–3 mm long anthers. The smooth, dark reddish-brown to orange-brown seeds resemble a nut, and are oblong to narrow and ovaloid in shape. They are about 3.0–4.5 mm long, and 1.2–1.9 mm in diameter.

Distribution

''Gahnia grandis'' originated in southern Australia. About 40 species are found in Australia, Asia, and the Pacific Islands. The species is found particularly in Western Australia, Queensland, New South Wales, Tasmania, and Victoria, where it is native to areas such as the Gippsland plain, Wilsons Promontory, and Highlands-Southern Fall bioregions. Past records in Victoria show it at only two possible sites: the Gembrook-Beenak area, and the northern part of Wilsons Promontory.


''Gahnia'' is common in Tasmania, which has seven native species of the plant. These species are widespread in wet forest, and are more frequently observed after fire. They are also found in coastal areas, sometimes also occurring in dry woodland.

''Gahnia rodwayi'', a small, grass-like plant found in the dry forests in the southeast of Tasmania, generally flowers between October and January. This species grows in moist soil beside water, in shady forest gullies and in dappled to semi-shade. ''Gahnia grandis'' is widespread in all regions of Tasmania except the midlands and the northeast, growing in poorly-drained soil types from sea-level to the mountains. It is also found on the margins of wetlands and forests, in riparian areas on button grass heaths, and along road cuttings and ditches.

Habitat

''Gahnia grandis'' originated in southern Australia. About 40 species are found in Australia, Asia, and the Pacific Islands. The species is found particularly in Western Australia, Queensland, New South Wales, Tasmania, and Victoria, where it is native to areas such as the Gippsland plain, Wilsons Promontory, and Highlands-Southern Fall bioregions. Past records in Victoria show it at only two possible sites: the Gembrook-Beenak area, and the northern part of Wilsons Promontory.


''Gahnia'' is common in Tasmania, which has seven native species of the plant. These species are widespread in wet forest, and are more frequently observed after fire. They are also found in coastal areas, sometimes also occurring in dry woodland.

''Gahnia rodwayi'', a small, grass-like plant found in the dry forests in the southeast of Tasmania, generally flowers between October and January. This species grows in moist soil beside water, in shady forest gullies and in dappled to semi-shade. ''Gahnia grandis'' is widespread in all regions of Tasmania except the midlands and the northeast, growing in poorly-drained soil types from sea-level to the mountains. It is also found on the margins of wetlands and forests, in riparian areas on button grass heaths, and along road cuttings and ditches.''Gahnia grandis'' is a very hardy, perennial grass species with woody rhizomes, which forms large tussocks. Most of the year it is found in moist soil, often subject to periodic inundation. Once it is established, cutting grass is drought and wind tolerant. The flowering season is from spring through summer. Seed maturity can be predicted by the colour of the flower head, the bright brown immature fruits turning black at maturity. At this stage they are ready for use in food preparation.

''Gahnia grandis'' is resistant to disease caused by the water mould ''Phytophthora cinnamomi'', but is highly flammable.

Many species in the family Cyperaceae, including cutting grass, are considered important as food sources and safe habitat for native birds, such as the currawong, native insects, moths, and butterflies, such as the chaostola skipper . The larvae of the choastola skipper feed nocturnally on ''Gahnia'' species, including ''Gahnia radula'' and ''Gahnia grandis''. The butterfly plays a vital role in pollination. Many other insects also feed exclusively on ''Gahnia'' species.

Cutting grass is dependent for seed dispersal on birds such as the currawong, which eat the fruit then regurgitate the partially-digested hard inner nut. One hypothesis is that germination is facilitated by contact with the birds' stomach acid, which weakens the tough seed coat.

Cutting grass is also a key habitat species for the rare and threatened Burnie burrowing crayfish .