Plants of
South Australia
Gahnia trifida
Cyperaceae
Coast Saw-sedge,
Cutting Grass
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Adelaide
Arkaroola
Ceduna
Coober Pedy
Hawker
Innamincka
Marla
Marree
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Oodnadatta
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Wudinna
Keith
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Botanical art

Kath Alcock painting: 1

Prior names

Cladium trifidum

Common names

Coast Saw-sedge

Cutting Grass

Etymology

Gahnia named after Dr. Henricus Gahn, 19th century Swedish botanist and student of Linnaeus. Trifida from the Latin 'trifidus' meaning split into three, referring to the 3-fid style.

Distribution and status

Found mainly in southern South Australia, with a disjunct population further north, growing on the margins of coastal saltmarsh or farther inland near saline and sub-saline lakes and watercourses. Also found in Western Australia, New South Wales, Victoria and Tasmania. Native. Common in South Australia. Rare in New South Wales. Common in the other States.
Herbarium regions: Lake Eyre, Eyre Peninsula, Northern Lofty, Murray, Yorke Peninsula, Southern Lofty, Kangaroo Island, South Eastern, Green Adelaide
NRM regions: Adelaide and Mount Lofty Ranges, Eyre Peninsula, Kangaroo Island, Northern and Yorke, South Australian Arid Lands, South Australian Murray-Darling Basin, South East
AVH map: SA distribution map (external link)

Plant description

Tussock-forming perennial sedge with culms to 100 cm high and 4 mm diameter. Leaves flat to inrolled, spreading; scabrous, longer than or equalling inflorescence. Inflorescence erect, narrow, to 70 cm long, yellowy to dark brown to black. Flowers in Spring. Fruits are light brown dense spike. Seeds are black three-sided ovoid seed to 3 mm long and 1.3 mm wide, with a fine pitted surface. Seed embryo type is capitate.

Seed collection and propagation

Collect seeds between December and February. Collect heads that are dying off and turning brown with obvious hard black seeds. Place the heads in a tray and leave to dry for one to two weeks. Then rub the heads with a rubber bung to dislodge the seeds. Use a sieve to separate any unwanted material. Store the seeds with a desiccant such as dried silica beads or dry rice, in an air tight container in a cool and dry place. From three collections, the seed viability was average to high, ranging from 55% to 100%.

This species has morphophysiological dormancy. The combination of dry heat (90 - 100°C) for 15 min, hydrogen peroxide and gibberellic acid treatments increased germination levels.

Seed collection and germination research for this species was supported by AMLR NRM in 2017-2018 and 1,500 plants will be propagated for reintroduction to Stipituris CP in 2019.

Seeds stored:
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LocationNo. of seeds
(weight grams)		Number
of plants		Date
collected		Collection number
Collection location		Date
stored		% ViabilityStorage
temperature
BGA1,100 (1.29 g)623-Jan-2007DJD752
Kangaroo Island		1-Aug-200795%-18°C
BGA2,950 (4.42 g)1-Feb-2008Bryan Haywood
South Eastern		19-Sep-2008100%-18°C
BGA11,000 (14.89 g)40+18-Feb-2016DJD3328
South Eastern		2-May-201755%-18°C
BGA5,400 (8.57 g)25-Feb-2016D250216SL
Southern Lofty		2-May-201785%-18°C
Location: BGA — the seeds are stored at the Adelaide Botanic Gardens, MSB — the seeds are stored at the Millennium Seed Bank, Kew, England.
Number of plants: This is the number of plants from which the seeds were collected.
Collection location: The Herbarium of South Australia's region name.
% Viability: Percentage of filled healthy seeds determined by a cut test or x-ray.
Germination table:
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We acknowledge the contributions of the South Australian Seed Conservation Centre, the Botanic Gardens of South Australia, and the Department for Environment and Water.